Field of Science

Algal Intrafamilial Strife

Most of you are probably familiar with the old adage that one should keep one's friends close and one's enemies closer. From a phylogenetic perspective, the red algal genus Plocamium has certainly achieved the latter.

Plocamium species growing on the coast of South Africa, copyright Derek Keats.


Plocamiaceae is a cosmopolitan family of marine red algae found mostly in temperate waters. They may grow in a variety of habitats from sheltered to exposed. Phylogenetic analyses have indicated that the family is somewhat distantly related to other red algal families, such that it is currently classified in its own order (Saunders & Kraft 1994). The great majority of the forty-odd known species of Plocamiaceae are currently placed in the genus Plocamium. These are reasonably sized seaweeds with erect or decumbent thalli that can grow about half a metre in length/height. They have flattened, complanately branched axes (that is, the branches are in the same plane as the axis they branch from). Branching is pectinate (comb-like) with each axis producing usually between two and six branchlets. The lower branchlets in a series are usually unbranched but higher ones will produce their own series of side-branchlets. In particular, the last branchlet will generally grow and overtop the axis it arose from to effectively replace it (as a result, the axis of the algal thallus will appear at first glance to have many more side branches than mentioned previously but can be seen on close inspection to have something of a zig-zag appearance representing the successive axes). The comb-like pattern of the branching is particularly evident in terminal branches of the thallus. In section, the axes have a disorganised cortex surrounding the central axial cells. Plocamiaceae have the standard triphasic red algal life cycle with gametophytes and sporophytes similar in outward appearance. Cystocarps appear to be more or less globular and borne along axial margins. Tetrasporangia are borne on the underside of modified branchlets called stichidia in a manner reminiscent of the sporangia of ferns (Gabrielson & Scagel 1989).

Close-up on terminal brachlets of Plocamium coccineum, copyright Fernan Federici. Some tetrasporangia-bearing stichidia are visible in the lower part of the image.


Only a few species have been described to date of the other genus of Plocamiaceae, Plocamiocolax. Though its reproductive anatomy demonstrates its relationship to Plocamium, Plocamiocolax is very different in its superficial appearance. It is a parasite, specifically a parasite of its sister genus. As such, they exhibit greatly reduced thalli and coloration. They grow on the host Plocamium as wartlike cushions, up to about five millimetres in diameter. As the cushion grows, it produces short, flattened projections that may be simple or forked. Tetrasporophytes may bear tetrasporangia on greatly reduced stichidia or on partially endophytic, verrucose patches.

Plocamiocolax pulvinata growing on Plocamium, copyright Michael Hawkes.


Parasitic forms that are closely related to the species they infect are referred to as 'adelphoparasites', meaning 'sister-parasites'. Adelphoparasitism is remarkably common among red algae: of over sixty known genera of parasitic red algae, about 90% are adelphoparasites (Salomaki & Lane 2014). One of the very first posts I ever wrote on this site was about red algal adelphoparasites, way back in...(gosh, really?...doesn't time fly when you're marching unceasingly towards oblivion...) It is possible that the regularity of this phenomenon is related to a distinctive feature of red algal development: the ability to open connections between adjacent cells allowing the passage of cytoplasm and organelles. Though the primary function of this process is presumably to facilitate the transfer of cellular products between cells of a single individual, it is not difficult to imagine a scenario where one individual hijacks another. The more closely related the adjacent cells, the greater the chance of an illicit connection succeeding. And succeeding multiple times. Though treated as a distinct genus, 'Plocamiocolax' lineages have apparently arisen within Plocamium multiple times (Goff et al. 1996). In some cases, a Plocamiocolax species proves to be the direct derivative of the Plocamium species they are found infesting. In others, a Plocamiocolax has arisen on one host species but later made the switch to another. Children are supposed to become independent and find their own way in the world, but sometimes the blighters just won't leave.

REFERENCES

Gabrielson, P. W., & R. F. Scagel. 1989. The marine algae of British Columbia, northern Washington, and southeast Alaska: division Rhodophyta (red algae), class Rhodophyceae, order Gigartinales, families Caulacanthaceae and Plocamiaceae. Canadian Journal of Botany 67: 1221–1234.

Goff, L. J., D. A. Moon, P. Nyvall, B. Stache, K. Mangin & G. Zuccarello. 1996. The evolution of parasitism in the red algae: molecular comparisons of adelphoparasites and their hosts. Journal of Phycology 32: 297–312.

Salomaki, E. D., & C. E. Lane. 2014. Are all red algal parasites cut from the same cloth? Acta Societatis Botanicorum Poloniae 83 (4): 369–375.

Saunders, G. W., & G. T. Kraft. 1994. Small-subunit rRNA gene sequences from representatives of selected families of the Gigartinales and Rhodymeniales (Rhodophyta). 1. Evidence for the Plocamiales ord.nov. Canadian Journal of Botany 72: 1250–1263.

Air-breathing Limpets

For many people, the most familiar members of the gastropods are the terrestrial snails. Gastropods started their evolution as marine animals, breathing through gills, but members of one lineage would instead evolve their own version of a lung, a large hollow in the mantle cavity opening through a hole alongside the head called the pneumostome. Possession of this lung cavity would enable slugs and snails to thrive in the terrestrial environment but the structure had originally evolved in a marine context, and even today one may find marine lung-bearers occupying habitats along the coast. One such group is the siphon limpets or 'false limpets'* of the Siphonarioidea.

*You know, normally I don't overly concern myself with vernacular names. They are not regulated and not obliged to follow reason. But even so, the name 'false limpet' makes me grit my teeth. The name is presumably inspired by the fact that siphonariids are not direct relatives of the 'true' limpets of the Patellogastropoda. But the limpet morphotype, where the typical spiral gastropod shell is reduced to a simple cap, has evolved on multiple occasions. As well as the siphonariids and patellogastropods, there are the keyhole limpets of the Fissurellidae, the freshwater limpets of the Ancylini, and many others, all consistently referred to as 'limpets'. The name refers to a morphology, not to a clade, and by that measure the siphonariids are no more 'false' than any other limpets.

Flat siphon limpets Siphonaria atra, copyright Ria Tan.


Living siphonarioids are placed within a single family, the Siphonariidae, whose members with their cap-shaped, often radially ribbed shells are found in littoral environments in temperate and tropical regions of the world. A second family, the Acroreiidae, is recognised from the Cretaceous and early Tertiary; the inclusion of these smooth, thin shells in the Siphonarioidea is somewhat tentative (classification of limpets in the fossil record is always a challenge because their simple shell form renders them light on distinguishing characters). Siphonariids are readily distinguished from other living limpets by the presence of a groove on the underside of the right side of the shell marking the position of the pneumostome. In dorsal view, this groove is often indicated by an asymmetry in the outline of the shell with one side produced. The pneumostome is also associated with a broad gap in the ring of muscle holding the shell in place; the ring is more complete in other limpets. Seemingly as a result of this lower extent of muscle, siphonariids cling to their home rocks with less tenacity than other limpets and are mostly restricted to more sheltered locations (Simone & Seabra 2017). On the other hand, they do have a more flexible foot than their competitors, allowing them to potentially move more quickly. Like other limpets, siphonariids are grazers, scraping microalgae as they crawl about. Siphonariids have a weaker radula than patellogastropods and so scrape somewhat less forcefully; when members of the two clades occupy the same habitats, patellogastropods are generally the more abundant. The majority of siphonariids (where known) have planktonic larvae but some species are known to be direct developers.

Siphonaria lessonii, copyright Mikelzubi.


Obviously, the marine but lung-possessing siphonariids are potentially of great interest in understanding how the gastropod lung evolved. Many earlier researchers thought that the siphonariids may have evolved from terrestrial ancestors who had returned to the seashore but this is no longer thought likely to be the case. In most lunged gastropods, gas exchange is effected in the mantle cavity via dense blood vessels in the cavity wall but in siphonariids a gill structure is present within the lung (this lung-gill combination makes the siphonariids particularly well suited for moving freely both above and below the water surface). The gill of siphonariids is quite similar to that of the sacoglossans, a group of herbivorous sea-slugs. Though it was long presumed that the lung-bearing gastropods belonged to a single clade, more recent molecular phylogenies have confused the issue (Kocot et al. 2013). The sacoglossans are likely to be close to the ancestry of lunged gastropods as a whole, but it is possible that siphonariids are more closely related to the sacoglossans than the other lung-bearers. It remains an open question whether the siphonariid combination of lung and gill represents an intermediate stage towards the vascular lung of the terrestrial forms, or whether siphonariids and other lung-bearers each evolved their pneumostome from close but distinct ancestors.

REFERENCES

Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

Simone, L. R. L., & M. I. G. L. Seabra. 2017. Shell and body structure of the plesiomorphic pulmonate marine limpet Siphonaria pectinata (Linnaeus, 1758) from Portugal (Gastropoda: Heterobranchia: Siphonariidae). Folia Malacologia 25 (3): 147–164.

The Colletinae: Going to Ground

In a recent post, I considered one of the families of short-tongued bees, the Halictidae. In this post, I'll turn my attention to members of one of the other short-tongued bee families, the Colletidae. Specifically, I'm looking at members of the subfamily Colletinae.

Mating ball of male ivy bees Colletes hederae, copyright Charles J. Sharp.


Members of the Colletidae differ from other bee families in that their glossa, the 'tongue' at the end of the proboscis, is apically bilobed or bifurcate. They are also distinctive in lining their nests with a plasticky, cellophane-like material. It has been thought that this material was made from dry saliva but the bulk of it is now known to come from a large gland in the abdomen that opens near the base of the sting (Almeida 2008). A nesting female will swallow droplets of the glandular secretion from her partially protruded sting then regurgitate it as she licks the wall of the nest cell. This waterproof lining both protects the cell from outside elements while preventing the loss of moisture from within. Many colletids, including colletines, leave the cell food provisions in a semi-liquid state; other bees whose nests are less watertight will dry and compact the provisions, presumably because the bulk of them would otherwise be lost before the larva hatched. In colletines, the egg is attached to the cell lining when laid, suspended above the provisions for the hatching larva to swandive into upon emergence. All colletids are solitary nesters with species nesting either in burrows in the ground or in hollows in vegetation; the majority of colletines are ground nesters*.

*One species, Colletes daviesianus, has apparently taken in Germany to boring its nests in the sandstone and mortar used in building construction.

Female Colletes daviesianus, copyright Donald Hobern.


In his 2007 edition of The Bees of the World, Charles Michener recognised five subfamilies within the Colletidae. The Colletinae were distinguished from three of these subfamilies by their retention of a covering of dense hair over the body (from the last subfamily, the Diphaglossinae, they differ in features of the glossa and wing venation). The hind leg of the female bears a well-developed scopa (dense arrangement of hairs for the carrying of pollen) on the femur and tibia with a corbicula (bare patch within the scopa where a ball of compacted pollen may be carried) on the underside of the femur. Hairiness is an ancestral characteristic for bees and phylogenetic studies have established that the Colletinae as recognised by Michener is a paraphyletic grouping (e.g. Almeida & Danforth 2009). As a result, it has been further subdivided with the name 'Colletinae' now restricted to what Michener had recognised as the tribe Colletini. As such, the Colletinae now includes just two genera of moderate-sized bees (seven to sixteen millimetres in length). The larger of these, Colletes, is found in temperate and tropical regions around the world except for the Indo-Australian region where it is notably absent. The other genus, Maurecolletes, is restricted to South America. One of the most distinctive features of Colletinae in the strict sense compared to other ex-colletines is the lack of the basitibial and pygidial plates, flattened and hardened plates possessed by other hairy colletids at the base of the hind tibia and at the end of the abdomen.

The absence of these plates is intriguing in light of the ground-nesting habits that seem to be the norm for Colletes (the nesting habits of Maurecolletes seem to be unknown). In other ground-nesting bees, the basitibial and pygidial plates are used to press the soil of the nest walls and opening into place. One would think this would mitigate against their loss. An explanation may be provided by the fact that some South American Colletes nest in the hollows of dead, pithy plant stems instead of in the ground, a characteristic shared with members of the less hairy colletid subfamilies belonging to the sister group of the colletines (Almeida & Danforth 2009). Ground-nesting Colletes species also bear noteworthy resemblances to stem-nesting colletids. Nest cells are closed with a layer of the cellophane-like wall membrane rather than the earthen plugs used by other ground-nesting bees. In many species, cells are lined up in a burrow divided by transverse partitions rather than placed in their own individual side branches. The possibility has been suggested that stem-nesting arose within the common ancestors of modern colletines and less hairy colletids. Ground-nesting in Colletes would then represent a secondary reversion by these species to the previous habit. When they did so, they retained the adaptations and habits that had originally been associated with their time in the twigs.

REFERENCES

Almeida, E. A. B. 2008. Colletidae nesting biology (Hymenoptera: Apoidea). Apidologie 39: 16–29.

Almeida, E. A. B., & B. N. Danforth. 2009. Phylogeny of colletid bees (Hymenoptera: Colletidae) inferred from four nuclear genes. Molecular Phylogenetics and Evolution 50: 290–309.

Michener, C. D. 2007. The Bees of the World 2nd ed. John Hopkins University Press: Baltimore.

Colpochila: The Chafing of a Mega-genus

Just a few weeks ago, I discussed the melolonthines, a hyperdiverse group of beetles including the chafers that have historically presented something of a taxonomic challenge. In the comments on that post, Adam Yates brought up one aspect of the difficulties presented by this group that I hadn't gotten around to discussing. This is the presence among melolonthines of a number of what may be called 'mega-genera', large genera containing literally hundreds of species that defy attempts to break them down into more manageable units. So on that note, it's only appropriate that I move on to an example of one of these mega-genera, Colpochila.

Colpochila obesa, from Insects of Tasmania.


Colpochila is an Australian genus of melolonthines belonging to a group currently recognised as the tribe Liparetrini (Britton 1986) though readers of the earlier post may recall that relationships between Australian melolonthines and taxa elsewhere in the world remains something of an open question. Liparetrins are, on the whole, a fairly generalised group: characters of the group include a lack of metallic coloration, a labrum which sits underneath and is not fused to the clypeus, simple claws, and relatively broad hind tibiae that end in a pair of widely separated spurs that are placed one above and one below so that the tarsus when moved from side to side can move between the spurs. The two largest genera in the tribe, by a significant margin, are Colpochila and Liparetrus. Somewhere in the region of 130 species are currently recognised in Colpochila whereas Liparetrus is even more diverse. However, both genera were referred to by Britton (1986) as 'polythetic': that is, both represent assemblages of species that, while clearly connected to each other overall, are difficult to characterise from a diagnostic perspective. Species of the genus possess enough features in common that we can readily recognise them as related but it is difficult to drill down on any individual feature or set of features that is shared between all species without exception. Similarly, while I can say from experience that it is generally easy to tell at a glance whether a given species is a Colpochila or a Liparetrus, it is a lot harder to actually define what separates the two genera. The most obvious distinction is size: Colpochila species are relatively large chafers, over a centimetre in length, whereas Liparetrus are smaller. Other features that each separate most Colpochila species from most (though not all) Liparetrus are circular eyes (most Liparetrus have eyes with flattened edges in back so the eye is closer to semi-circular), antennae with more segments in the terminal club, longer elytra that leave less of the end of the abdomen exposed, and hind coxae without the translucent margins found in many Liparetrus.

The lifestyles of Colpochila species are still not very well known. As with other melolonthines, most of the life is spent underground with mature adults only emerging very briefly to breed. The active adults fly at night and may be attracted to lights; it seems unclear whether they feed at maturity. This genus is mostly found in drier habitats such as open woodland, grasslands or semi-desert (mind you, this is Australia we're talking about; drier habitats are 90% of what's going). Of the known species, over half are found in Western Australia.

A second Colpochila species, from Friends of Queens Park Bushland.


So why are Colpochila and other melolonthine mega-genera so diverse? It should be noted that straight geographical and/or ecological divergence does not appear to be the reason: not only is it possible to find multiple species of a single genus in one location but one may even collect very similar species together. It might be that the diversity of the mega-genera is artefactual, a reflection of the failure of taxonomists to properly identify relationships: any study that wanted to explain their diversity would have to study their phylogenetic relationships with related smaller genera to confirm their evolutionary coherence and/or age of divergence. However, if the current generic classification of melolonthines reflects a real evolutionary pattern, a potential explanation was proposed by Britton (1986). Adult melolonthines do not emerge immediately upon maturing but remain dormant underground awaiting a suitable environmental signal such as rainfall. However, rainfall in the arid zone at any one time is often uneven. Dormant beetles at one spot may feel the urge to emerge while others nearby may be left to wait for the next shower. The first wave will have died off before the second wave emerges, and their offspring will not yet be mature. As a result, sub-populations in a single region may become temporally staggered allowing the possibility of divergence via genetic drift. Eventually, their emergence times may drift back into sync but by then they may no longer be able to breed successfully. Could this be the reason why so many species may be found in a single location or may other factors be more significant?

REFERENCE

Britton, E. B. 1986. A revision of the Australian chafers (Coleoptera: Scarabaeidae: Melolonthinae) vol. 4. Tribe Liparetrini: genus Colpochila. Australian Journal of Zoology, Supplementary Series 118: 1–135.

Austrotritia: Jack-in-the-Box Mites

We just keep coming back to the oribatids, don't we?

In an earlier post, I introduced you to Oribotritia, one of the genera of box mites. These, you may recall, are the armoured mites that have evolved the ability to curl the front of the body under themselves and tuck back their legs to form a solid case (in the Oribotritiidae, that mechanical defense is supplemented by the production of a defensive chemical, chrysomelidial, from glands in the cuticle—Shimizu et al. 2012). In the earlier post, I also gave you a quick overview of the families of what are known as the 'true' box mites. Today's post is for another component of the family Oribotritiidae, the genus Austrotritia.

Austrotritia lebronneci, copyright R. Penttinen.


Austrotritia accounts for nearly twenty species of box mite, the great majority of which are found in Australasia and southern and eastern Asia (Liu et al. 2009). Outliers are A. engelbrechti in South Africa, A. herenessica in the Canary Islands and, most unexpected of all, A. finlandica in Finland. Austrotritia differs from all other oribotritiids except the small Bornean genus Terratritia in lacking any division between the genital and aggenital plates on the underside of the body. The distinction between Austrotritia and Terratritia perhaps requires reassessment: Niedbała (2000) distinguished them by the presence of five-segmented palps and a single pair of exobothridial setae in Austrotritia versus three-segmented palps and two pairs of exobothridial setae in Terratritia (the bothridia are the structures bearing large sensory setae on the prodorsum of the mite; exobothridial setae are thus setae sitting alongside the bothridia). However, Liu & Zhang (2014) redescribed the widespread species Austrotritia lebronneci as having three-segmented palps but only a single pair of exobothridial setae. Note that classification of oribatids has mostly been conducted from a diagnostic rather than a phylogenetic perspective; it would not surprise me if Terratritia turned out to be a derived subgroup of Austrotritia.

Schematic of jump performance by Indotritia cf. heterotrichia from Wauthy et al. (1998); the solid line represents observed jumps, the dashed lines modelled jumps. Line drawings represent (a) body posture when beginning jump, (b) rotation during jump, and (c) enclosed posture after jumping.


As well as the aforementioned defenses standard for box mites, Austrotritia and the related genus Indotritia stand out from other oribotritiid genera in that at least some species have the ability to jump. The mechanics of jumping were described for a species of Indotritia by Wauthy et al. (1998) who recorded the mites jumping nearly a centimetre in height over a distance of just under an inch (for perspective, the mite itself is about half a millimetre in length). Jumping was preceded by compressing the notogaster while raising the ventral plates under the opisthosoma, together with lowering the prosoma and bringing the legs together under the body. Small hooks at the end of femur of the first pair of legs were used to catch ridges on the side of the prodorsum in order to hold the body compression. The force for the jump was presumably supplied by the release of the hydraulic compression of the body fluids when the legs disengaged from the prodorsum, propelling the mite backwards while the body rolled forwards: essentially, the mite would star-jump away. The mite would curl up after jumping to lie in an enclosed state.

Whether all Austrotritia species are jumpers is not entirely certain. The femoral hooks that seem to play a significant role in jumping have not been described in all species. However, it is not clear if this lack of observation represents an actual absence or whether this minute feature has simply been overlooked. I also wonder whether the aforementioned fusion of the ventral plates in Austrotritia is related to their jumping abilities (Indotritia species also have the genital and aggenital plates fused anteriorly though they retain a degree of separation at the rear of the plates; non-jumping Oribotritia have the plates entirely separated). As always, there's still a lot we could potentially find out.

REFERENCES

Liu, D., J. Chen & G. Qiao. 2009. Review of Austrotritia (Acari: Oribatida: Oribotritiidae), with descriptions of two new species from China. Zootaxa 2144: 54–64.

Liu, D., & Z.-Q. Zhang. 2014. Redescription of Austrotritia lebronneci (Oribotritiidae) and descriptions of two new species of Euphthiracaridae (Acari, Oribatida) from Australian region. International Journal of Acarology 40 (1): 43–51.

Niedbała, W. 2000. The ptyctimous mites fauna of the Oriental and Australian regions and their centre of origin (Acari: Oribatida). Polskie Towarzystwo Taksonomiczne: Wrocław (Poland).

Shimizu, N., R. Yakumaru, T. Sakata, S. Shimano & Y. Kuwahara. 2012. The absolute configuration of chrysomelidial: a widely distributed defensive component among oribotritiid mites (Acari: Oribatida). Journal of Chemical Ecology 38: 29–35.

The Cervini: Deer of Temperate Eurasia (and Beyond)

A couple of years back, I presented you with a post giving a quick overview of the classification of deer. For this post, I'm going to look a bit closer at a particular subgroup of deer: the species of the tribe Cervini.

Wapiti Cervus canadensis, photographed by Mongo.


For most people outside the Americas, a member of the Cervini will probably represent the first image that comes to mind when picturing a deer. The same goes for many Americans, for that matter, though in that part of the world they face a bit more competition. Cervins are the most diverse group of deer in temperate Eurasia, with representatives also being found in northernmost Africa, North America, India and southeast Asia (as well as introduced species in Australasia). The Monarch of the Glen was a cervin: specifically, a red deer Cervus elaphus. Bambi, in his Disney film incarnation, was also a cervin, a wapiti C. canadensis (in his original literary form, probably less familiar to modern audiences with little interest in Austrian novels about all the miserable ways that animals can die, he was a roe deer Capreolus capreolus and so not a cervin) (Edit: Scratch that, he's a apparently a non-cervin white-tailed deer, see comment below). The group has long been recognised by features of the skull and leg bones, and also is well supported by molecular data (Heckeberg 2020). Males produce antlers with multiple branches (at least in typical individuals) with the branches or tines usually directed forwards from the main shaft of the antler (the Père David's deer Elaphurus davidianus differs from other cervins in having the tines directed rearwards). The first of these branches, the brow tine, usually originates close to the base of the antler. In a number of Asian species, such as the chital Axis axis and sambar Cervus unicolor, there is usually on one more branch on the antler so each antler ends with three points. Species with such antlers are generally found in dense forests and their simpler antlers may represent an adaptation to these habitats (Heckeberg 2020). Other cervin species may have more extensively branched antlers with a tendency for antler complexity to correlate with overall body size; the largest living cervins, the red deer and wapiti, also have the most branched antlers. Larger extinct species had even more extravagant headgear with the apex of insanity being perhaps the bush-antlered deer Eucladoceros dicranios of the lower Pleistocene of Europe: each antler of this species might carry a dozen points.

Skull of Eucladoceros dicranios, photographed by Aldo Cavini Benedetti.


To describe the classification of cervins as having recently been in a state of flux is something of an understatement. A conservative presentation of the group may refer to thirteen or fourteen living species in four genera (e.g. Macdonald 1984). More recent authors, however, might refer to up to ten genera and nearly forty species. In a way, this difference is not really as dramatic as it may seem: multiple subspecies have long been recognised for most cervin species and some authors have argued for the recognition of many of these 'subspecies' as distinct species. Classification at generic level has mostly been affected by recognition that the genus Cervus as previously recognised is not monophyletic. Most recent authors agree on the recognition of at least four genera of Cervini (Cervus, Dama, Axis and Rucervus) with two further genera (Rusa and Elaphurus) also commonly recognised.

Persian fallow deer Dama mesopotamica, copyright Rufus46.


The genus Dama is usually recognised as including two species, the fallow deer D. dama and Persian fallow deer D. mesopotamica. These species are readily distinguished from other cervins by the form of their antlers which are distally palmate. Palmate antlers are also characteristic of the extinct giant Irish elk Megaloceros giganteus and many recent authors have regarded the two as closely related. The white spots that many deer species possess when young are commonly retained by fallow deer into adulthood though the coat will often become darker and the spots disappear during winter. Melanistic and leucistic individuals of fallow deer are also common. Defining the native range of the fallow deer is a bit of a tricky question. This inhabitant of open woodlands is currently widespread in Europe but was probably restricted to a region of the eastern Mediterranean during the last ice age. Its current range in northern Europe may in large part be the result of human transportation. The fallow deer has also been widely introduced elsewhere: herds may now be found in numerous locations in Africa, Australasia, North and South America. The Persian fallow deer, in contrast, is now endangered, its range restricted to a small number of localities in Iran. Indeed, it was once thought to be extinct prior to the rediscovery of a population of about two dozen individuals in the mid-1950s; the current population is perhaps only a few hundred.

Thorold's deer Cervus albirostris, copyright Heather Paul.


The genus Cervus in its current, more restricted sense includes the red deer and wapiti as well as the sika C. nippon* of eastern Asia. Sika are generally smaller than the other two species and, like fallow deer, usually retain the juvenile spots into adulthood. Excluding occasional small accessory branches, the antlers of sika also possess no more than four tines (Heckeberg 2020) in contrast to the commonly further branched antlers of red deer and wapiti. Four-tined antlers are also characteristic of the Thorold's or white-lipped deer C. albirostris, an inhabitant of the Tibetan Plateau that has sometimes been treated recently as the only representative of a separate genus Przewalskium. White-lipped deers have broad, cow-like hooves for navigating the steep, rocky slopes of their homeland. More commonly accepted classification-wise is the separation of two species found in southern Asia, the rusa C. rusa and sambar C. unicolor, as the genus Rusa. Both these species have three-tined antlers and their fawns lack spots.

*Commonly referred to as the sika deer. 'Sika' (or, as it's more commonly transliterated these days, 'shika') is Japanese for deer, so the common vernacular name of Cervus nippon is, indeed, 'deer deer'. The same issue arises for the rusa deer in Malay.

Chitals Axis axis, copyright Charles J. Sharp.


Axis is a genus of four species of smaller forest-dwelling deer found in southern Asia. Antlers are generally three-tined with the upper beams curving inwards towards each other. The chital remains spotted at maturity whereas the other species loose their spots. These species include the hog deer A. porcinus, named for its low, short-legged build, and two closely related insular species. Recent years have seen some authors separate the hog deers as a separate genus Hyelaphus, restricting Axis to the chital, owing to molecular phylogenies casting doubt on the genus' monophyly. However, it seems that these studies may have been mislead by a contaminated sample for the hog deer (Gilbert et al. 2006) and other studies have retained a monophyletic Axis. The thamin Rucervus eldii and barasingha R. duvauceli are also found in southern Asia where they tend to be associated with marshy habitats. Their antlers curve outwards then inwards to form a bow-shaped curve; those of the thamin are three-tined whereas the barasingha possesses further tines, sometimes up to ten on each antler. Again, some studies have questioned the monophyly of Rucervus and suggested the thamin be moved to a separate genus Panolia.

Père David's deers Elaphurus davidianus, copyright Peter O'Connor.


Finally, there is Père David's deer, arguably the weirdest of all the cervins, most often placed in its own genus Elaphurus but sometimes included in Cervus. By the time this species became known to European naturalists, it was already extinct in the wild, surviving only as a herd kept in a hunting garden near Peking belonging to the emperor of China. This herd was exterminated during the Boxer Rebellion but specimens that had been transported to Europe saved the species from total extinction. It is now widely kept in captive herds and has also been returned to the wild in a couple of locations in China. Père David's deer has a number of features that make it stand out from other deer: as well as the aforementioned backwards antlers, it has wide, splayed hooves and a remarkably long tail. But in other regards, Père David's deer is not anywhere as weird as it should be. In particular, its karyotype is very similar to that of the red deer: close enough, in fact, that not only are the two species capable of hybridising in captivity but the resulting hybrids are fully fertile (such matings are unlikely in the wild owing to the two species normally having different breeding seasons). Heckeberg (2020) found that Père David's deer was associated with Cervus species in analyses of nuclear genes and cranial characters but with Rucervus species in analyses of mitochondrial genes and dentition; other authors had previously found similar results. It has been suggested that these schizoid tendencies with regard to phylogenetic analysis might indicate a hybrid origin for Père David's deer from ancestors related to the wapiti on one side and the thamin on the other. Such a hybridisation event would have happened some time ago—fossils related to Père David's deer seem to date back at least to the late Pliocene—allowing enough time to pass for the new population to develop its own idiosyncracies not acquired directly from either parent.

Sticking Your Sulphur on the Outside

The ability to obtain energy from sunlight through photosynthesis is a feature of a range of bacterial lineages, using a number of different processes and growing under a variety of different conditions. Perhaps the best known such group is the oxygen-producing blue-green algae or Cyanobacteria, but there are other photosynthetic bacteria that do not release oxygen. One such group is the purple sulphur bacteria of the Ectothiorhodospiraceae.

Individual Ectothiorhodospira mobilis, from Trüper (1968).


Purple sulphur bacteria are members of the hyperdiverse array of bacteria known as the Proteobacteria, specifically of a subgroup known as the Gammaproteobacteria (other notable Gammaproteobacteria include such luminaries as the various Pseudomonas species, the plant-attacking Xanthomonas, and perhaps the single most intensely studied bacterial species of all, Escherichia coli). They are found growing under anoxic conditions, using light energy to assimilate carbon via the oxidation of sulphides to organic sulphur, which is in turn further oxidated to sulphate. Purple sulphur bacteria can be divided between two families, the Chromatiaceae and Ectothiorhodospiraceae, that may be distinguished by how they deposit the sulphur globules produced during photosynthesis. In Chromatiaceae, the sulphur globules are retained within the cell membrane but in Ectothiorhodospiraceae, they are deposited externally (one species of Ectothiorhodospiraceae, Thiorhodospira sibirica, does deposit sulphur both internally and externally, but the internal globules are restricted to the peripheral region of the cell within the periplasmic space). Photosynthetic pigments are bacteriochlorophyll a or b, together with carotenoids; these pigments are attached to intracellular membranes appearing as lamellar stacks. Ectothiorhodospiraceae species are found in marine and other saline habitats, often in environments with a more or less alkaline pH. Species of the genus Halorhodospira, which have been found in salt and soda lakes, require exceedingly saline conditions, being unable to grow at total salt concentrations below 10%.

Cross section of Ectothiorhodospira mobilis showing photosynthetic membrane stack, from Trüper (1968).


Though the genera Halorhodospira and Thiorhodospira are strictly anaerobic and invariably photosynthetic, some species of the genus Ectothiorhodospira are able to obtain energy heterotrophically from organic compounds, and may grow under microaerobic conditions in the dark. The range of organics they can utilise in this way is limited to relatively simple compounds: they generally cannot break down carbohydrates, for instance, but they can grow on organic acids such as acetates. Molecular analysis has also indicated the inclusion in the Ectothiorhodospiraceae of a number of non-photosynthetic bacteria. The species Arhodomonas aquaeolei was originally isolated from brine from a subterranean oil reservoir; it breaks down organic compounds using oxygen or nitrate but has the same limitations to simple molecules as Ectothiorhodospira. It seems easy to imagine it evolving from an Ectothiorhodospira-like ancestor but losing its photosynthetic capabilities due to its subterranean habitat, like an animal in a cave losing its eyesight. The genera Nitrococcus and Thioalkalivibrio are lithoautotrophs (that is, they synthesis organic compounds like photosynthetic forms but use the energy from chemical reactions using minerals rather than from light) and generally aerobic (at least one strain of the species Thioalkalivibrio denitrificans is facultatively anaerobic). Thioalkalivibrio species oxidise sulphur, sulphides and other sulphur-containing compounds whereas Nitrococcus convert nitrate to nitrite. Despite their lack of photosynthetic abilities, Nitrococcus still carry indications of their photosynthetic ancestry in the presence of tubular intracellular membranes, the repurposed derivatives of the original stacks.

REFERENCE

Brenner, D. J., N. R. Krieg & J. R. Staley (eds) 2005. Bergey’s Manual of Systematic Bacteriology 2nd ed. vol. 2. The Proteobacteria pt B. The Gammaproteobacteria. Springer.

Chondria: Turf of the Surf

Of the major groups of multicellular algae (or 'seaweeds' in the common parlance) found in the world today, the red algae are unquestionably the most speciose. In this post, I'm looking at a widespread genus of red algae going by the name of Chondria.

Chondria coerulescens, copyright Alan Thurbon.


Chondria is a genus of fifty or more known species of marine algae belong to the Rhodomelaceae, one of the most diverse families of red algae, found in tropical and temperate regions of the world. Species vary in size and are found in a range of habitats from intertidal to subtidal. They may live attached to rock or growing over other seaweeds. Turfs of Chondria may form a significant part of local habitats, but like many smaller red algae they tend not to receive a great deal of attention from humans (I did come across webpages referring to it as a weed in marine aquaria). In the majority of Chondria species, the thallus is erect; more rarely, it grows prostrately against its substrate or free-floating. The thallus is attached to the substrate by a discoid holdfast or by haptera growing from stolons. The greater part of the thallus is filamentous and more or less irregularly branched. The branches may be cylindrical and compressed; the younger branches are often constricted at their bases. The tips of the branches may end in a depression or in a tapering filament. Structure-wise, filaments are solid in cross-section without internal hollows. A central axial cell is surrounded by a ring of five pericentral cells, with the outside of the filament composed of smaller cortical cells.

Like other red algae, Chondria species have a complicated triphasic life cycle. The haploid gametophytes are dioecious: that is, there are separate male and female individuals. Males produce flat, disc-shaped or slightly lobed spermatangia that release male gametes. Female gamete-producing structures grow from the base of lateral filaments on the thallus; fertilised female gametes grow into a diploid, more or less ovoid cystocarp that remains attached to the parent gametophyte. Diploid spores released by the cystocarp grow into independent tetrasporophytes. These produce haploid spores by meiosis that will be released and grow into new gametophytes, and the cycle begins again.

REFERENCE

Womersley, H. B. S. 2003. The Marine Benthic Flora of Southern Australia. Rhodophyta—Part IIID. Ceramiales—Delesseriaceae, Sarcomeniaceae, Rhodomelaceae. Australian Biological Resources Study: Canberra, and State Herbarium of South Australia: Adelaide.

Crystal Butterflies of the Sea

All chains of life in the open ocean are ultimately dependent on plankton. Photosynthetic micro-plankton convert the energy of sunlight into their own stores that are in turn commandered by animal plankton through consumption and digestion. Both animal and photosynthetic plankton provide food sources for larger animals, both plankton and nekton, and even deeper dwelling organisms may take their sustenance from the rain of planktonic corpses settling from above. A wide range of animal lineages may be identified among oceanic plankton, one of the most prominent being the gastropod group known as the Thecosomata.

An orthoconch thecosomatan, Clio pyramidata, copyright Russ Hopcroft.


The Thecosomata are small gastropods, rarely exceeding a couple of centimetres in size at their largest. Many marine molluscs will spend at least part of their lives as planktonic larvae but relatively few mollusc groups have taken the route that the Thecosomata have, remaining part of the plankton through their entire life cycle. They maintain their position in the plankton by means of broad expansions of the foot on either side of the mouth, known as parapodia. The appearance and movement of these parapodia have given the Thecosomata the vernacular name of 'sea butterflies'. They also inspired the name Pteropoda ('wing-foot'), used for a clade that unites the Thecosomata with another group of planktonic gastropods, the Gymnosomata. Historically, many authors have questioned the association of the pteropods, in part because of the differing dispositions of the parapodia in the two component groups (Gymnosomata, commonly known as 'sea angels', have the wings of the parapodia located further back on the body rather than around the mouth). Nevertheless, more recent studies have corroborated pteropod monophyly (Klussmann-Kolb & Dinapoli 2006). The Thecosomata themselves fall between two major sublineages, known as the Euthecosomata and Cymbulioidea (or Pseudothecosomata). Members of the Euthecosomata have well-divided parapodia and the viscera are contained within a delicate, translucent, calcareous shell. In some euthecosomes such as the genus Limacina, this shell is coiled like that of other gastropods, but in others the shell has become straight and bilaterally symmetrical, being conical or globular with lateral projections. Recent phylogenetic analysis suggests that the straight-shelled sea butterflies may form a single monophyletic lineage known as the Orthoconcha* (Corse et al. 2013). In the Cymbulioidea, the parapodia are fused around the front of the animal to form a single swimming plate. Of the three families of cymbulioids, the Peraclidae have a calcareous shell as in the euthecosomes. The Cymbuliidae shed the larval calcareous shell over the course of their development and replace it with a pseudoconch, a hardened gelatinous, slipper-shaped structure that is still secreted by the mantle. In the third family, the Desmopteridae, the shell has been lost entirely.

*In the early days of invertebrate palaeontology, pteropod affinities were suggested for a number of groups of early Palaeozoic conical shells of uncertain affinities, such as the hyoliths and tentaculitoids. It is worth noting that, at the time, the pteropods themselves were often thought to represent a distinct molluscan class independent of the gastropods. Such proposals have long since fallen by the wayside. Not only is there nothing to connect such Palaeozoic forms with modern pteropods but the most superficial of resemblances in overall shape to certain Orthoconcha, but all indications now are that the Orthoconcha themselves did not evolve until some time in the Cenozoic (Corse et al. 2013), leaving a gap of some hundreds of millions of years between them and their erstwhile forebears.

Cymbulia peronii, copyright Vincent Maran.


Live sea butterflies feed on a wide range of organisms, including both micro-algae and other planktonic animals. The ancestral radula is reduced or lost and prey is captured by means of a mucous web, globular in euthecosomes and a funnel-shaped sheet in cymbulioids (Gilmer & Harbison 1986). This web may be absolutely gigantic relative to the animal itself, reaching up to two meters in diameter. While the web is extended, the sea butterfly does not swim actively but hangs suspended in the water column below, drawing food into the mouth by means of tracts of cilia on lobes of the foot. A further mucous array may trail away from the animal containing faecal particles and/or particles rejected as food; this may keep such particles from re-entering the feeding web. Should the animal be disturbed, the mucous web is rapidly ingested or abandoned before swimming away. Sea butterflies have commonly been referred to as suspension feeders but Gilmer & Harbison (1986) noted that a case could potentially be made for considering them as predators. Though micro-algae make up a large proportion of thecosome gut contents, the mucous web allows them to also capture active prey such as copepods that might have otherwise eluded them. It is possible that such prey is in fact more important overall for satisfying the sea butterfly's nutritional requirements. A number of sea butterflies possess brightly coloured mantle appendages that may lure active prey; the faecal trails may also assist in this way.

Limacina helicina, copyright Russ Hopcroft.


Sadly, any discussion of Thecosomata is forced to end on a tragic note. Recent increases in atmospheric carbon dioxide have lead to oceanic waters becoming more acidic than previously, which in turn reduces the concentration of dissolved carbonate. Because carbonate is a vital component of molluscan shells, ocean acidification compromises shell production. Studies of recent thecosome samples show that their shells have become thinner and more porous as acidification increases (Roger et al. 2012). If this trend continues, we may reach a point where shell secretion becomes impossible for these animals, leading to tragic consequences both for the thecosomes themselves and for the countless other organisms ecologically dependent on them. In recent years, concern has been expressed that ecological degredation may mean that we can no longer see butterflies flying in our gardens; their marine analogues are no less vulnerable.

REFERENCES

Corse, E., J. Rampal, C. Cuoc, N. Pech, Y. Perez & A. Gilles. 2013. Phylogenetic analysis of Thecosomata Blainville, 1824 (holoplanktonic Opisthobranchia) using morphological and molecular data. PLoS One 8 (4): e59439.

Gilmer, R. W., & G. R. Harbison. 1986. Morphology and field behavior of pteropod molluscs: feeding methods in the families Cavoliniidae, Limacinidae and Peraclididae (Gastropoda: Thecosomata). Marine Biology 91: 47–57.

Klussmann-Kolb, A., & A. Dinapoli. 2006. Systematic position of the pelagic Thecosomata and Gymnosomata within Opisthobranchia (Mollusca, Gastropoda)—revival of the Pteropoda. Journal of Zoological Systematics and Evolutionary Research 44 (2): 118–129.

Roger, L. M., A. J. Richardson, A. D. McKinnon, B. Knott, R. Matear & C. Scadding. 2012. Comparison of the shell structure of two tropical Thecosomata (Creseis acicula and Diacavolinia longirostris) from 1963 to 2009: potential implications of declining aragonite saturation. ICES Journal of Marine Science 69 (3): 465–474.

The Halictidae: Short Tongues and Waxy Chambers

In an earlier post, I introduced you to the diverse group of bees known as the Halictinae. In this post, I'm going to take a step back and consider the family of bees to which the halictines belong, the Halictidae.

Nomia sp. feeding at a flower, copyright Graham Wise.


The Halictidae are one of the families of what are known as 'short-tongued bees' (the other short-tongued families recognised by Michener, 2007, are the Andrenidae, Colletidae and Stenotritidae). Bees have their mouthparts modified compared to those of other wasps to form a mobile proboscis. The tongue works in three main sections from base to tip. The first two sections work like the upper and lower parts of your arm, or of the arm of a crane, to extend and fold back the proboscis against the underside of the head. The third section beyond these two includes a flexible structure, the glossa, that may be thought of as working like the tongue proper to collect nectar and pollen from the inside of flowers. Somewhat self-explanatorily, this glossa is extremely long and slender in the families of 'long-tongued bees' (the Apidae and Megachilidae) but relatively shorter and broader in short-tongued bees. Naturally, these differences in tongue structure may be reflected in differences in which types of flowers the different types of bees chose to visit. Just to confuse matters, some species of Halictidae may have relatively long proboscides overall, but in this case the extra length is achieved by extending the length of the middle 'arm' section rather than of the glossa itself. The primary features separating Halictidae from the other families of short-tongued bees relate to the structure of particular sclerites incorporated into the proboscis that I'm not going to go into here, but notable points include that the glossa of Halictidae is pointed at the tip and hairs on it are usually branched or bifid at the tips.

Male Halictus tetrazonianellus with proboscis extended (the glossa is the orange structure at the end of the proboscis), copyright Gideon Pisanty.


For the most part, halictids are moderately built bees: neither remarkably slender nor particularly robust. Halictids vary extensively in size: many are small, even minute, but some may be relatively large by bee standards. Coloration is similarly variable, with both metallic and non-metallic species belonging to the family. Members of the genus Nomia (which tend to be relatively large for halictids) often bear contrasting bright bands across the back of the metasoma. Michener (2007) recognised four subfamilies within the halictids: the Rophitinae, Nomiinae, Nomioidinae and Halictinae, with the Halictinae being considerably more diverse species-wise than the other three. Nomioidines have sometimes been included by other authors within the Halictinae but, as there is a general agreement that nomioidines form the sister lineage of the halictines in the strict sense, the question of whether to combine them or not is purely a matter of semantics. Rophitines differ from other halictids in having a relatively large labrum whose tip remains visible between the mandibles when they are closed (other subfamilies have the labrum hidden by the closed mandibles). Rophitines, as well as kleptoparasitic halictines, also have the tip of the labrum simply truncate or rounded; in other subfamilies, the tip of the labrum in females is produced into a distinct process. Rophitines also have the scopa (the array of long pollen-carrying hairs on the hind leg) less developed on the trochanter and femur than on the tibia whereas other subfamilies (excluding, again, kleptoparasitic forms in which the scopa is reduced) generally have the longest scopal hairs on the femur. Nomiines commonly have the third submarginal cell on the wing (if present) as long as the first submarginal cell or at least more than twice the length of the second. In nomioidines and halictines, the third submarginal cell is much shorter. Another notable feature of the last two subfamilies is that the basal vein (the upper of the three veins radiating from the basal midline of the wing) is much more strongly curved near the base than in other bee families; this feature may or may not be discernable in rophitines and nomiines.

Just to show that bees can sometimes get insane: a male of the Colombian species Chlerogella anchicaya, from Engel et al. (2014).


For the most part, halictids construct their nests in burrows in the ground (some halictines nest in rotting wood). Cells of the burrows are generally lined with a wax-like membrane secreted by the parent bee. The membrane is duller and less watertight in Rophitinae than in other subfamilies; one rophitine genus, the southwest North American Protodufourea, appears to not produce such a membrane. Most non-halictine halictids are solitary nesters though some nomiines are known to work communally, and may even show low levels of division of labour. Kleptoparasitism is not known outside the Halictinae.

REFERENCE

Michener, C. D. 2007. The Bees of the World 2nd ed. John Hopkins University Press: Baltimore.

The Melolonthinae: Chafers and June Bugs

Within the bewildering array that is beetle diversity, one of the more readily recognisable groups is the Scarabaeoidea, the assemblage that includes dung beetles (which, as it happens, are what I currently spend most of my days looking at) and related forms. Members of this group are easily distinguished from other beetles by their distinctive antennae, ending in an asymmetrical club with segments extending to one side like a set of fingers. Several families, many of them further subdivided into subfamilies, are currently recognised within the scarabaeoids. One of the most commonly encountered scarabaeoid subgroups is the subfamily Melolonthinae, commonly known as the chafers.

Green scarab beetles Diphucephala sp., a common genus of day-flying melolonthines here in Australia, copyright Boobook48.


Somewhere in the region of eleven thousand species around the world have been assigned to this grouping; as always, doubtless many more could be recognised by those who take the time. Melolonthinae is generally recognised as a subfamily of the family Scarabaeidae, sharing with other scarabaeids features such an antennal club in which the segments are relatively narrow and can be smoothly pressed against each other, and an exposed pygidium (the last dorsal plate on the abdomen, forming what you might think of as the 'butt plate'). Some authors have recognised melolonthines as a distinct family but this is the less commonly utilised option. Melolonthines belong to a group of mostly plant-feeding subfamilies in which the row of abdominal spiracles bends downwards towards the rear so at least the last pair remains visible when the elytra are closed. Within this cluster, melolonthines tend to be characterised more by lacking the features of the other subfamilies than by distinctive features of their own (more on that in a moment) but general features include mandibles that are not visible when looking down on the top of the head, fore coxae that do not protrude much ventrally, equal claws on each leg (at least on the mid and hind legs) and only one visible spiracle when the elytra are closed. The labrum (the piece at the front of the mouthparts that might be thought of as the insect's top lip) is usually hardened and may be more or less fused with the clypeus (the lower- or foremost section [depending how you look at it] of the front of the head capsule). Many melolonthines are noticeably hairy and/or dull in comparison with other scarabaeoids but others may be shiny and/or metallic in coloration.

Sugarcane white grub beetle Lepidiota stigma, copyright Bernard Dupont.


For the most part, melolonthines are plant-feeders at both larval and adult stages of the life cycle (Lawrence & Britton 1991). The greater part of the active life cycle is taken up by the larval stage which may last for many months (Britton 1957). Larvae mostly live underground, feeding on plant roots and humus. A number of species have made themselves known as significant pests in this manner because of the damage they may inflict on pastures or agricultural crops (the grass grub Costelytra zealandica comes immediately to mind as a good example of this in my native New Zealand). Pupation also occurs underground in subterranean cells and mature adults may remain dormant in these cells for some months waiting for conditions to be just right for emergence. Once they do emerge from the ground, however, the adult life span is quite brief, only lasting a few weeks or even days. Because of this brief emergence, and because their habit of waiting for specific environmental cues means that large numbers may appear seemingly all at once, many species have been awarded vernacular names that reflect their seasonality such as June bug (in the Northern Hemisphere) or Christmas beetle (in the Southern). Some species will feed on foliage as adults, some may visit flowers for pollen and nectar, other particularly short-lived species will not feed as adults at all. The majority of adult melolonthines are active at dusk or night, spending the days sheltered in secluded locations, but a number of flower-feeding species are active by day (Britton 1957).

The infamous grass grub Costelytra zealandica, illustrated by Desmond Helmore.


The classification of melolonthines can charitably be described as an absolute mess. As noted above, we can confidently say that they belong to a clade with other subfamilies of plant-feeding scarabaeids (the Cetoniinae, Rutelinae and Dynastinae) but the features setting them apart from these other subfamilies are likely to be primitive for the group. As such, it comes as little surprise that phylogenetic studies have failed to establish the Melolonthinae as monophyletic (e.g. Eberle et al. 2018; Woolley 2016). However, it seems that no-one thinks that an adequately expansive study that would allow them to be appropriately divvied up has yet been done. Matters are not helped by the absence of a well-established internal classification for melolonthines. Various distinct subgroups can be recognised and between twenty or thirty tribes have been recognised around the world. But the relationships between these tribes remain uncertain, as does the tribal position of many genera. Much of the revisionary work that has been done has been conducted at a regional level only. Thus, for instance, the tribal classification of Australian melolonthines established by Britton (1957) applies only to Australian species and the tribal distinctions Britton recognised may end up falling apart if one attempted to apply them to species from elsewhere. Not that the authors should be criticised for this situation: after all, when one is dealing with over 11,000 species, things rapidly tend to become unmanageable.

REFERENCES

Britton, E. B. 1957. A Revision of the Australian Chafers (Coleoptera: Scarabaeidae: Melolonthinae) vol. 1. British Museum (Natural History): London.

Eberle, J., G. Sabatinelli, D. Cillo, E. Bazzatto, P. Šípek, R. Sehnal, A. Bezděk, D. Král & D. Ahrens. 2018. A molecular phylogeny of chafers revisits the polyphyly of Tanyproctini (Scarabaeidae, Melolonthinae). Zoologica Scripta 48: 349–358.

Lawrence, J. F., & E. B. Britton. 1991. Coleoptera. In: CSIRO. The Insects of Australia: a textbook for students and research workers 2nd ed. vol. 2 pp. 543–683. Melbourne University Press.

Woolley, C. 2016. The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa. African Invertebrates 57 (1): 53–66.

The Ornithocheyletiini: Making a Living off Birds

In an earlier post, I commented on the carnivorous mites of the family Cheyletidae. These rapacious micropredators are commonly associated with the nests and burrows of terrestrial vertebrates, attacking debris-feeders drawn in by the host's leavings. With such a close association already in place, it should come as little surprise that some lineages within the Cheyletidae have learnt to bypass scavenger predation and go directly to the source, becoming parasites of the vertebrate hosts themselves.

Slide-mounted female of Bakericheyla chanayi (left; scale bar = 50 µm) and nest webs on the skin of a heavily parasitised chaffinch Fringilla coelebs (right), from Filimonova (2013).


One such lineage is the Ornithocheyletiini, members of which are parasites of birds. Like other parasitic cheyletids, ornithocheyletiins have a relatively small, simple gnathosoma (the 'head' of the mite), no eyes, and lack the large, pectinate, claw-like setae found on the palps of free-living predatory cheyletids (instead, the setae at this position are small and smooth though they do still have hooked ends). Ornithocheyletiins are further distinguished from other cheyletids by having particularly large claws at the end of each leg that are overhung by a well developed knob on the end of the tarsus (Bochkov & Fain 2001).

Ornithocheyletiins live on the skin of their bird hosts. In the genera Ornithocheyletia and Bakericheyla, the mites spin a protective web beneath which they live and feed. Members of the tribe have been recorded from a number of bird orders, mostly smaller land birds (Passeriformes, Columbiformes, Piciformes, Coraciiformes, Psittaciformes and Apodiformes). At least one species of Ornithocheyletia was described from the Natal spurfowl Pternistis natalensis, a galliform. Members of the genus Apodicheles are restricted to species of Apodiformes (swifts) but other genera are found on a wider range of hosts. One cosmopolitan species, Bakericheyla chanayi, has been found on hosts of both the orders Passeriformes and Coraciiformes. The exact method of exploiting their host may vary: species of Bakericheyla feed on blood whereas Ornithocheyletia species feed on lymph fluid.

Historically, parasitic cheyletids were treated as a separate family Cheyletiellidae but are now classified with their free-living relatives. The exact relationships between free-living and parasitic cheyletids remain open to question. A morphological phylogenetic analysis of cheyletids by Bochkov & Fain (2001) did recover the parasitic forms as a clade but this result was questioned by the authors themselves. Instead, they suggested that the various parasitic tribes of Cheyletidae represented independent lineages whose shared features represented convergent adaptations to the parasitic lifestyle. The Ornithocheyletiini might, for instance, be compared to tribes such as the Cheletosomatini that inhabit the quills of bird feathers but feed on other quill-inhabiting mites rather than the birds themselves. Did ornithocheyletiins evolve from using birds as hunting grounds to using birds as food, or did they carry their parasitic habits with them from some other host?

REFERENCE

Bochkov, A. V., & A. Fain. 2001. Phylogeny and system of the Cheyletidae (Acari: Prostigmata) with special reference to their host-parasite associations. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Entomologie 71: 5–36.

Variations on a Tayra

Subspecies can be a funny thing in the world of animal taxonomy. Millions of litres of ink have been spilt over the years arguing over how one defines a species but a lot less has been invested in discussing the nature of subspecies. For some popular species concepts (such as the most popular iteration of the 'phylogenetic species concept'), one might question whether any concept of subspecies could be applied at all (I could suggest some hypothetical situations but just how applicable or practical they are is a further matter). Essentially, most subspecies concepts distill down to 'a population that is distinct enough to warrant recognition but somehow doesn't quite qualify as a species'. Historically, the rank has tended not to receive a lot of usage among animals outside groups subject to particularly high levels of taxonomic attention—most particularly, vertebrates and butterflies—and many currently recognised animal subspecies were first named in days when taxon descriptions tended to be much briefer and taxonomists were under less pressure to explain their reasoning. Because subspecies tend to be, by their nature, vague and difficult to define, and because evaluating them often requires detailed population analysis within a species, these historical subspecies have a tendency to linger, unchallenged, in taxonomic listings. And with that as background, tayras.

Tayra Eira barbara photographed in Peru, copyright eMammal. Photography location would indicate this individual to be either E. b. madeirensis or E. b. peruana.

The tayra Eira barbara is a large mustelid (a member of the family including weasels, otters and badgers) found in warmer regions of Central and South America, its distribution extending down to about the level of the southern edge of Brazil. They are long-bodied but robust animals, kind of looking like a 'roided-up stoat. They grow to a head-body length of two feet or more (up to about 71 centimetres) with a tail about two-thirds as long again. Adult males tend to be a third as large again as females and more muscular around the fore quarters. Comparisons have often been made between tayras and the martens Martes of the Northern Hemisphere and molecular studies confirm a relationship between these two genera, as well as the wolverines Gulo. Closer fossil relatives are known from North America and it seems likely that the tayra originated on that continent then spread southwards. Ruiz-García et al. (2013) suggested that the degree of genetic divergence between tayras found in South America might indicate the species may have arrived there about eight million years ago, before the formation of the Panamanian land bridge. Tayras are not the only species for which this possibility has been suggested; these early arrivals may have reached South America by island-hopping between earlier-emerging segments of the eventual connection.

Tayras are diurnal omnivores, their known diet ranging from fruits to small animals to honey. In captivity, it seems they will accept pretty much anything offered to them. Tayras are the only animals other than humans that have been recorded caching unripe fruit in order to eat it after it finishes ripening. It is still not certain to what degree tayras are solitary or social; though commonly regarded as solitary, they have been recorded hunting howler monkeys in groups (Shostell & Ruiz-Garcia 2013). Tayras are mostly found in forests; in some areas they may adjust to more open habitats but seemingly only under sufferance (Presley 2000). Though not regarded as 'arboreal' per se, tayras are adept climbers. Their well developed carpal vibrissae ('whiskers' on the wrists) presumably contribute to this ability. Their wide distribution and adaptability mean that tayras are not currently regarded as of conservation concern though habitat degradation has reduced their numbers in some areas.

Tayra from Belize, presumably the light-headed Eira barbara senex, from Wikimedia Commons.


The body and tail of tayras are generally dark brown or black with the head being distinctly lighter in coloration (light brown or grey to yellow). Leucistic and albino individuals are not that uncommon (yellow tayras are apparently particularly common in Guyana). A patch of pale coloration, varying from a spot to a broad triangle, is often (but not always) present on the chest and throat. Recent taxonomic listings (e.g. Presley 2000) have recognised seven subspecies of tayra distinguished by coloration. The Mexican Eira barbara senex has a greyish white head with the light coloration extending to dark yellow shoulders and a dark brown body. Eira barbara inserta, found in southern Honduras and Nicaragua, is a dark subspecies with a dark brown head, black body and no throat patch. The Colombian E. b. sinuensis is darker than E. b. senex with the nape a darker brown than the head; it may or may not possess a throat patch. Eira barbara barbara, found in southern Brazil, eastern Bolivia and Paraguay, is lighter than E. b. sinuensis but darker than E. b. senex and has a yellowish throat patch. The northern Brazilian E. b. madeirensis is a chocolate brown with the head slightly lighter than the body; again, a throat patch may or may not be present. The Peruvian and western Bolivian E. b. peruana is similar to the last subspecies but has darker legs and a black tail. Finally, E. b. poliocephala, which has a distribution centred on the Guianas, is similar to E. b. barbara but with a darker yellow throat patch and yellow shoulder patches that sometimes merge with the throat patch to form a complete collar.

Tayra photographed in a zoo in Panama, copyright Dirk van der Made. Being a zoo individual, its origins are a bit more open than the other individuals shown on this page, but Panama is home to Eira barbara inserta and E. b. sinuensis.


Such is the received wisdom as recorded by Presley (2000) but does it accurately reflect population distributions? Ruiz-García et al. (2013) conducted an analysis of mitochondrial genes from tayras representing the five South American subspecies (i.e. excluding E. b. senex and E. b. inserta). They found that of these five subspecies, only E. b. poliocephala (as represented by specimens from French Guiana) could potentially be differentiated genetically. Samples from the ranges of the other four 'subspecies' were intermingled in analyses, leading Ruiz-García et al. to suggest that they should be merged into a single subspecies E. b. barbara (it may also be worth me mentioning that, when I was looking for images to illustrate this post, I had difficulty finding ones in which the supposed differences between subspecies were recognisable). Of course, that leaves the status of the two Central American subspecies undetermined. It may be of note that they seem to be more distinct in appearance than some of the hitherto-recognised South American subspecies but it remains to be seen just how significant this is.

REFERENCES

Presley, S. J. 2000. Eira barbara. Mammalian Species 636: 1–6.

Ruiz-García, M., N. Lichilín-Ortiz & M. F. Jaramillo. 2013. Molecular phylogenetics of two Neotropical carnivores, Potos flavus (Procyonidae) and Eira barbata (Mustelidae): no clear existence of putative morphological subspecies. In: Ruiz-Garcia, M., & J. M. Shostell (eds) Molecular Population Genetics, Evolutionary Biology and Biological Conservation of Neotropical Carnivores pp. 37–84. Nova Publishers: New York.

Shostell, J. M., & M. Ruiz-Garcia. 2013. An introduction to Neotropical carnivores. In: Ruiz-Garcia, M., & J. M. Shostell (eds) Molecular Population Genetics, Evolutionary Biology and Biological Conservation of Neotropical Carnivores pp. 1–34. Nova Publishers: New York.

Actinobacteria: From Monads to Moulds

Perhaps no field of biology was revolutionised more by the advent of molecular phylogenetics in the 1990s than bacteriology. Previously, the higher classification of bacteria and their analysis from an evolutionary perspective had mostly an unattainable dream. Though some major groups such as cyanobacteria and spirochetes possessed biochemical and ultrastructural features that had already set them apart, most bacterial lineages could not be robustly associated with each other much above about the genus level. Molecular phylogenetics changed that, allowing the recognition of a number of genetically supported diverse lineages that, between them, divvied up the greater number of described bacterial species. One of the first of these lineages to be formally recognised was the Actinobacteria.

Colour-enhanced SEM of Streptomyces griseus hyphae, from the Actinomycetes Society of Japan.


Actinobacteria are one of the major lineages of what had already been recognised as the Gram-positive bacteria, so called because they can be stained with crystal violet using the technique developed by Hans Christian Gram. The absorption of this stain is not a mere sartorial manner: it relates to the structure of the cell wall which in typical Gram-positive bacteria has a thick layer of peptidoglycan outside the cell membrane (standard Gram-negative bacteria have a thinner peptidoglycan layer and a second cell membrane overlaying it). In some texts from the 1990s, you may encounter the Actinobacteria being referred to as the 'high G+C Gram-positive bacteria', in reference to a tendency for the genomes of these bacteria to have a relatively high proportion of cytosine and guanine. As it turns out, this feature is not universal within the actinobacterial lineage, but this group remains recognisable by phylogenetic analysis, gene arrangements, and the presence of distinctive indels and inserts in certain genes (Goodfellow et al. 2012).

Many Actinobacteria have a filamentous growth habit and an assemblage of these forms had been recognised even before the molecular revolution as the 'actinomycetes'. However, the diversity of cell forms among the Actinobacteria ranges from spherical cocci to complex branching hyphae forming a fungus-like mycelium. Mycelial forms may form complex sporulating structures, sometimes distinctive enough to make them among the relatively few bacteria that may be identified by their external morphology alone. Their selections of habitat run the gamut but the highest diversity of species may be found in soils under aerobic conditions. Thermophilic and anaerobic Actinobacteria are much less numerous. Most are chemo-organotrophs, obtaining energy from the break-down of organic compounds.

Goodfellow et al. (2012) recognised a division of the phylum Actinobacteria between six classes. The largest of these classes includes by far the majority of actinobacterian species and goes by the name of...wait for it...Actinobacteria. Yes, apparently bacterial nomenclature sees no problem with having 'phylum Actinobacteria' and 'class Actinobacteria' co-existing in the same classification but not referring to the same assemblage of organisms. This. Is. Insane. Even a scan of Goodfellow et al.'s own text provides examples of the name being referred to without the rank explicitly specified. Seriously, how could anyone even begin to consider this acceptable? The remaining classes–Acidimicrobiia, Coriobacteriia, Nitriliruptoria, Rubrobacteria, Thermoleophilia–each contain only a handful of descried species but, as always with bacterial taxonomy, doubtless countless more remain to be described. Members of one of these classes, the Nitriliruptoria, were not described at all before 2009.

It is hardly surprising that a group as diverse as Actinobacteria should include many representatives of significance to humans. For a start, their status as one of the most diverse groups of soil-living bacteria means that they play a major role in decay processes. A number of species are pathogens of plants and animals; perhaps the most notorious of these are Mycobacterium species such as the tuberculosis-causing M. tuberculosis and the leprosy-causing M. leprae. Members of the genus Frankia are found living in nodules on the roots of certain plants where they provide the host with nitrates by fixing nitrogen from the air. Actinobacteria are also massively significant from a biochemical point of view. Actinobacteria species produce close to half of the known microbial bioactive secondary metabolites (Goodfellow e tal. 2012) and about two-thirds of all known antibiotics (Barka et al. 2016). Particularly significant (providing over 80% of all known actinobacterial antibiotics) in this regard are the various species of Streptomyces, which are also among the most morphologically complex Actinobacteria. When conditions under which Streptomyces mycelia are growing begin to decline, cells within the terrestrial vegetative hyphae will begin to die off in order to provide nutrients to support the growth of spore-producing aerial hyphae. As noted by Barka et al. (2016), production of antibiotics at this time would help to prevent other micro-organisms from swooping in to take advantage of this flood of suddenly released nutrients. I hardly need point out how much the discovery of antibiotics changed the pace of medical progress; it might be argued that our modern society simply could not exist without them. Without Actinobacteria, you might not be alive to read this today.

REFERENCES

Barka, E. A., P. Vatsa, L. Sanchez, N. Gaveau-Vaillant, C. Jacquard, J. P. Meier-Kolthoff, H.-P. Klenk, C. Clément, Y. Ouhdouch & G. P. van Wezel. 2016. Taxonomy, physiology, and natural products of Actinobacteria. Microbiology and Molecular Biology Reviews 80 (1): 1–43.

Goodfellow, M., P. Kämpfer, H.-J. Busse, M. E. Trujillo, K. Suzuki, W. Ludwig & W. B. Whitman (eds) 2012. Bergey's Manual of Systematic Bacteriology 2nd ed. vol. 5. The Actinobacteria, Part A and B. Springer.