Field of Science

The Ant-like Beetles

As I've commented before, the world is home to an overwhelming diversity of small brown beetles, most of them (for me, at least) inordinately difficult to distinguish. One group of tiny beetles that is quite recognisable, though, is the ant-like beetles of the genus Anthicus.

Anthicus cervinus, copyright Robert Webster.


Over a hundred species around the world have been attributed to this genus. Few of them grow more than a few millimetres in length. They are elongate with the elytra more or less rounded and often covered in short hair. The legs are relatively long. The prothorax is globular and generally narrower towards the base. The head is inclined and carried on a narrow neck (Ferté-Sénectère 1848). Many species have the elytra contrastingly patterned with bands or spots. As the vernacular name indicates, the overall appearance is reminiscent of a small ant though I'm not sure if this indicates a protective mimicry or is merely coincidence.

Anthicus antherinus, copyright Udo Schmidt.


The natural history of most Anthicus species is poorly known. The greater number of species are saprophages, found in association with rotting vegetation or scavenging on dead insects. One species, Anthicus floralis, is found worldwide as a storage pest, infesting seed and grain stores. One of the larger North American species, A. heroicus, has larvae that attack masses of dobsonfly eggs on midstream boulders (Davidson & Wood 1969). The larvae feed on the eggs from the inside, using them for shelter as well as nutrition, before emerging from the eggs to pupate.

REFERENCES

Davidson, J. A., & F. E. Wood. 1969. Description and biological notes on the larva of Anthicus heroicus Casey (Coleoptera: Anthicidae). Coleopterists Bulletin 23 (1): 5–8.

Ferté-Sénectère, M. F. de la. 1848. Monographie des Anthicus et genres voisins, coléoptères hétéromères de la tribu des trachélides. Sapia: Paris.

The Camisiids: Cryptic Inhabitants of Soil and Wood

Various views of Camisia biverrucata, copyright Pierre Bornand.


The animal in the above pictures is a typical representative of the Camisiidae, a widely distributed family of oribatid mites. Members of this family can be found in soil, on the trunks of trees, or hidden among mosses and lichens. They are slow-moving animals and are often concealed from potential predators by an encrusting layer of dirt and organic debris. Carrying this encrusting layer may be related to a reduction in the offensive chemical-producing glands that are used by many other oribatids for defense (Raspotnig et al. 2008). In members of the genus Camisia, the openings of these glands are completely covered by dirt, but in the genera Platynothrus and Heminothrus the openings still protrude above the encrustation. The recently described Paracamisia osornensis, which does not carry an encrusting layer, retains a large offensive gland (Olszanowski & Norton 2002).

Close to 100 species have been assigned to this family; though found in most parts of the world, camisiids are most diverse in the Northern Hemisphere. One species in particular, Platynothrus peltifer, is almost global in distribution and the range of habitats in which it has been found includes soil, litter, peat and even aquatic habitats (Norton & Behan-Pelletier 2009) When one is as small and metabolically undemanding as these animals are, there may be surprisingly little difference between being out in the air or immersed in water, and even primarily terrestrial oribatids may survive submersion almost indefinitely. Genetic studies of P. peltifer have identified a high level of within-species divergence and it has been calculated on this basis that this species may have survived almost unchanged in external appearance for some 100 million years (Heethoff et al. 2007).

The ubiquitous Platynothrus peltifer, copyright Centre for Biodiversity Genomics.


The Camisiidae are closely related to another oribatid family, the Crotoniidae, that is found in South America and Australasia. One of the more significant differences between the two families is that whereas the camisiids appear to be entirely parthenogenetic, crotoniids reproduce sexually. Recent analyses, both molecular and morphological, indicate that the 'camisiids' are paraphyletic with regard to the crotoniids, leading Colloff & Cameron (2009) to treat the latter as a subfamily, Crotoniinae, of the former. This re-classification has been accepted by other authors though the law of priority requires that the combined family should be known as the Crotoniidae, not Camisiidae. The nested position of the sexual crotoniines within the asexual 'camisiids', with other related oribatid families also being asexual, has led to the suggestion that the crotoniines have somehow re-evolved sexuality. This would be fascinating if true, seemingly violating the usual principle that complex features can't be re-evolved once lost. Personally, I tend to be sceptical of claims like this (see this old post, for instance). I would like to see evidence beyond simple phylogenetic position to indicate if this is a true re-evolution rather than an historical bias towards loss of sexuality giving a misleading image.

REFERENCES

Colloff, M. J., & S. L. Cameron. 2009. Revision of the oribatid mite genus Austronothrus Hammer (Acari: Oribatida): sexual dimorphism and a re-evaluation of the phylogenetic relationships of the family Crotoniidae. Invertebrate Systematics 23: 87–110.

Heethoff, M., K. Domes, M. Laumann, M. Maraun, R. A. Norton & S. Scheu. 2007. High genetic divergences indicate ancient separation of parthenogenetic lineages of the oribatid mite Platynothrus peltifer (Acari, Oribatida). Journal of Evolutionary Biology 20: 392–402.

Norton, R. A., & V. M. Behan-Pelletier. 2009. Suborder Oribatida. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 430–564. Texas Tech University Press.

Olszanowski, Z., & R. A. Norton. 2002. Paracamisia osornensis gen. n., sp. n. (Acari: oribatida) from Valdivian forest soil in Chile. Zootaxa 25: 1–15.

Raspotnig, G., E. Stabentheiner, P. Föttinger, M. Schaider, G. Krisper, G. Rechberger & H. J. Leis. 2008. Opisthonotal glands in the Camisiidae (Acari, Oribatida): evidence for a regressive evolutionary trend. Journal of Zoological Systematics and Evolutionary Research 47 (1): 77–87.

Fishing Mice

In a 1950 discussion of the origins of the fauna of South America, the great American palaeontologist G. G. Simpson dismissed the enormous radiation of muroid rodents in that continent as mere "field mice" exhibiting little regional differentiation. George Gaylord Simpson may have been one of the leading thinkers in mid-20th Century evolutionary theory, but in this respect he was just plain wrong. The South American mice and rats include a wide variety of divergent forms, some of them specialised in surprising ways. Consider, for instance, the fishing mice of the Ichthyomyini.

Illustration of Stolzmann's crab-eating mouse Ichthyomys stolzmanni by Joseph Smit.


The Ichthyomyini are a small assemblage of less than twenty species of mice found between Mexico and the north of South America from Peru to French Guiana (Voss 1988). Though some species are known from lower altitudes, the majority are found in alpine habitats in association with fast-flowing mountain streams (albeit in no location are they known to be common). Ichthyomyins seem to show a particular preference for hanging around waterfalls (Barnett 1997) and are not found in association with standing water such as swamps or ponds. They are moderate in size, ranging from ten to twenty centimetres in length excluding the tail. They show a number of adaptations for foraging underwater: the hind feet are partially webbed and have a more or less elongate fringe of stiff hairs that aid in swimming, the tail is furry rather than scaly, the eyes are small, the external ears are reduced in size (in a couple of species they are completely hidden by the fur and in one, Anotomys leander, the external pinnae are missing entirely), and the whiskers are long, strong, and arranged in such a way that they almost look more like the whiskers of a sea lion than of a mouse. The nerves associated with these whiskers are also enlarged and they evidently provide the main means of finding food.

Peruvian fish-eating rat Neusticomys peruviensis, copyright Carlos Boada.


Or, as I should say, finding prey. As far as we know, these mice seem to be entirely carnivorous. Only a couple of examples are known of specimens with plant matter in their stomachs and the significance of those finds remains uncertain. The primary source of food for most species is small invertebrates such as aquatic insects. Where freshwater crabs are available, a number of species show preferences for those. In larger species, the diet may be supplemented to a greater or lesser degree by small vertebrates such as fish or tadpoles. In line with their carnivorous diet, ichthyomyins are also characterised by a shorter, less complicated gut than other mice. Little is known about breeding and nesting habits in ichthyomyins. A specimen of Chibchanomys kept in captivity made tunnels in mossy vegetation (Barnett 1997). The few known specimens of gravid females indicate that litters are small with no more than two foetuses being carried at a time.

Voss (1988) recognised five genera of Ichthyomyini. The largest of these, Neusticomys, includes about half a dozen species that may more closely resemble the ancestral morphology for the group. Their hind feet are narrower than those of other ichthyomyins and the fringe of swimming hairs is shorter (Packer & Lee 2007). Where one species found in Colombia and Ecuador, Neusticomys monticolus, overlaps in range with Anotomys leander, it shows a preference for more sheltered sections of stream banks whereas A. leander is found in more exposed rapids.

Undescribed species of Chibchanomys, copyright Alexander Pari.


In most ichthyomyins, the coat consists of a layer of dense, woolly underfur covered by an overcoat of long guard hairs mixed with glossy, often distally flattened awn hairs. In Anotomys leander, Chibchanomys trichotis, and Neusticomys monticolus, the awn hairs are missing so these species have a dull grayish black appearance overall rather than than the glossy coat of other species. Chibchanomys trichotis retains minute external ear flaps albeit not ones that are visible past the coat; Anotomys leander, as noted above, lacks external ear flaps but does have the positions of the ear openings marked by a prominent white spot. Both these last two species were placed in monotypic genera by Voss (1988), but Barnett (1997) refers to an at-that-point undescribed species of Chibchanomys.

The remaining two genera were recognised by Voss (1988) as including four species apiece. Species of Rheomys, found in the mountains of Central America, have the most extensively webbed hind feet among the ichthyomyins. This is the only genus of fishing mice found in Central America; the other genera are all restricted to South America. The genus Ichthyomys includes the largest species of the group and also the species that feed on the highest proportion of vertebrates. This difference in diet is reflected in their dentition: Ichthyomys species have proportionately larger incisors and smaller molars than other ichthyomyins, with greater emphasis on using the incisors to grasp and slice struggling prey.

Rheomys raptor, from Villalobos-Chaves et al. (2016).


All told, the ichthyomyins are a remarkable radiation. Ecologically, they are close parallels to forms found elsewhere such as water shrews or desmans, but most other semi-aquatic mammals are distinctly larger in size. Even with less than twenty species, the ichthyomyins represent more species than there are of similarly sized semi-aquatic mammals anywhere else in the world. However, as noted above, ichthyomyins are not common anywhere they occur, and factors such as deforestation and climate change could represent a significant threat to their survival. It would be unfortunate if this remarkable radiation was to fade away.

REFERENCES

Barnett, A. A. 1997. The ecology and natural history of a fishing mouse Chibchanomys spec. nov. (Ichthyomyini: Muridae) from the Andes of southern Ecuador. Zeitschrift für Säugetierkunde 62: 43–52.

Packer, J. B., & T. E. Lee Jr. 2007. Neusticomys monticolus. Mammalian Species 805: 1–3.

Voss, R. S. 1988. Systematics and ecology of ichthyomyine rodents (Muroidea): patterns of morphological evolution in a small adaptive radiation. Bulletin of the American Museum of Natural History 188 (2): 259–493.

Seriously, What Is This Thing?

So there weren't too many people speculating about the identity of that mysterious figure (hi, Adam!) As it happens, there was a reason I'd put it out there: the reason being, I really don't have any idea what it is either.

Spinita spp., from Kordè in Koren' (2003). 1: S. sanashticgolica, 2: S. cryptosa, 3: S. spinoglobosa.


The figure comes from a Russian book, Атлас ископаемой фауны и флоры палеозоя Республики Бурятия ('Atlas of the Palaeozoic fossil fauna and flora of the Republic of Buryatia'), edited by T. N. Koren' and published in 2003 in Ulan-Udè. Buryatia is a Russian republic in south-eastern Siberia, wrapping around the eastern and southern coasts of Lake Baikal. The fossils shown above come from the Lower Cambrian (the Botomian stage in the Russian system) of the Eastern Sayan Mountains. Going by the appearance of the figures, I presume they're being examined as thin sections, a commonly used method for studying Palaeozoic microfossils. Though as microfossils go, these are definitely on the large side: the specimen figured as 1a is a centimetre long and three millimetres wide. The other specimens are smaller, about half a centimetre in length.

When I saw these figures, I was just mystified. Their describer, K. B. Kordè, regarded them as a new class of 'Nemathelminthes', claiming that 'the first impression that is created from the described material is that they are representatives of the Kinorhyncha or Gastrotricha'. I'm not sure that I would agree with that. I found myself wondering if they were even animals, though I was hard pressed to think what else they might be. Not being familiar with the interpretation of thin sections, the thought did cross my mind to ask how certain can we be that these are even fossils, but I think that may be a bit uncharitable. Kordè also suggested that a break in the apparent cuticle of the S. sanashticgolica specimen about halfway along the flattened side (interpreted as the venter) might be the mouth. If so, that would be very unlike any kinorhynch or gastrotrich I've heard of. Could be a flatworm, I suppose, though Kordè then goes on to read the cluster of spines at one end (as magnified in figure 2b) as marking the anus which would seem to put paid to that! Said spines, or papillae, or whatever, are also supposed to have medial channels that Kordè interprets as nephridia.

All in all, I can't express anything other than confusion about this one. Certainly I haven't been able to find any further commentary on these enigmas; a Google search for Spinita sanashticgolica brings up just one result, an offhand mention in this book which seems to be just referring to it as found in the same formation as another fossil. Confusingly enough, that mention seems to date from 1986, a good seventeen years before Koren' (2003) was even printed: whether that indicates that the latter publication was not actually the first time the description of Spinita saw print, or whether this genus saw time floating around in unpublished communications, I have no idea.

Name the Bug Revived

It's been a very long time since I last did one of these, and I'm not sure if I still have the readership for it, but I'm genuinely interested to know what anyone can make of this (attribution to follow):


Some necessary context: they're fossils, Cambrian in age, I presume being examined in thin section. The specimens numbered 1, 2 and 3 were described as three different species of a single genus. Even if you don't know exactly what it is, let me know what you think it might be...

Edit: Forgot to give an indicator of size. They're about the one-centimetre range in maximum breadth.

The Origins of a Closed Bolete

Boletes are a distinctive group of mushrooms in which the underside of the fruiting body is covered by tubular pores instead of gills. Though boletes are classified in the fungal order Boletales, not all members of this order produce bolete-type fruiting bodies (as exemplified in an earlier post). Consider, for example, the case of Gastrosuillus.

'Gastrosuillus' sp., copyright Danny Miller.


Gastrosuillus was recognised in 1989 for a small group of species found in North America that closely resembled members of the more typical bolete genus Suillus (the slippery jacks) except for their production of secotioid fruiting bodies, in which the pores are distorted and do not form a flattened plane, and may remain covered by an external membrane (secotioid fruiting bodies may be considered an intermediate form between typical mushrooms and the gastroid fruiting bodies of fungi such as puffballs). All Gastrosuillus species were extremely rare, known only from single locations or even single collections. Gastrosuillus suilloides and G. amaranthii were found in California, G. imbellus in Oregon, and G. laricinus in New York State. All four were found on the ground in conifer forest; fruiting bodies of G. suilloides could be buried (Bessette et al. 2000).

From its inception, a close relationship with and possibly even derivation from members of the genus Suillus seems to have been on the cards for Gastrosuillus. It should be noted that Suillus was not the only bolete genus with a secotioid satellite: as Gastrosuillus was to Suillus, so Gastroboletus was to Boletus, and Gastroleccinum was to Leccinum. So it should have come as little surprise when a molecular analysis of Gastrosuillus species by Kretzer & Bruns (1997) found them to be nested within Suillus, nor forming a single clade within that genus. Instead, the western species were well separated from the New York G. laricinus. As a result, Kretzer & Bruns advocated the synonymisation of the two genera.

Typical form of larch bolete Suillus grevillei, copyright Luridiformis.


But the demotions didn't stop there. Not only was Gastrosuillus laricinus nested molecularly within Suillus, it appeared to be nested within a particular species, S. grevillei (conversely, the California species form a distinct lineage that is, so far as we know, entirely secotioid; the Oregon G. imbellus has not been examined molecularly owing to difficulties in extracting DNA from the single known specimen). The sole known location for G. laricinus lies within the range of S. grevillei, with the two species having been found in close proximity, and the indications were that G. laricinus was a very recent derivative of S. grevillei or possibly even a mere growth variant. Again, this is not entirely without precedent. Secotioid variants have been recorded of other mushroom species, and secotioid-like forms of the agaricoid mushroom Lentinus tigrinus have even been shown to be the result of a recessive allele of a single gene. Kretzer & Bruns (1997) therefore suggested that G. laricinus be synonymised entirely with S. grevillei. This action does not appear to have gained universal acceptance (for instance, the two are provisionally treated as distinct by Bessette et al., 2000) but is certainly worthy of consideration.

REFERENCES

Bessette, A. E., W. C. Roody & A. R. Bessette. 2000. North American Boletes: A color guide to the fleshy pored mushrooms. Syracuse University Press.

Kretzer, A., & T. D. Bruns. 1997. Molecular revisitation of the genus Gastrosuillus. Mycologia 89 (4): 586–589.

Cliff Ferns

Historically, the higher classification of ferns has tended to be a bit wobbly. Compared to flowering plants, ferns often offer fewer readily observable features that may offer clues to relationships. As a result, the position of many fern taxa has long been uncertain. One such group is the cliff ferns of the genus Woodsia.

Woodsia scopulina, copyright Jim Morefield.


Cliff ferns, as their name suggests, are commonly found growing on rocks. There are a few dozen species, mostly found in cooler regions of the Northern Hemisphere. A single species, Woodsia montevidensis, extends into South America and southern Africa (Rothfels et al. 2012). They have short creeping rhizomes with a covering of scales and leaves bearing a mixture of scales and hairs. The most distinctive feature of the cliff ferns can only be seen on fertile fronds: the sori (spore packets) are covered by an indusium that is attached to the leaf basally relative to the sori. These indusia are commonly composed of an array of scales or filamentous sections, in contrast to the solid indusia of other ferns.

Underside of pinnule of Woodsia plummerae, showing the filamentous indusia, from here.


Historically, Woodsia has been placed in a family Woodsia with a number of superficially similar fern genera such as the bladder ferns of the genus Cystopteris. However, molecular phylogenetic analyses have disputed the monophyly of such a group. Rothfels et al. (2012) divided the 'woodsioid' ferns between no less than six different families with Woodsiaceae in the strict sense limited to the cliff ferns alone. Though some authors have divided the cliff ferns between multiple genera, an analysis of the group by Shao et al. (2015) found it difficult to reliably distinguish such subgroups and recommended recognition of only a single genus. They did, however, recognise three major clades within Woodsia identified by molecular phylogenetic analysis as distinct subgenera. The type subgenus Woodsia is distinctive among ferns in possessing articulated stems; species of this subgenus are widespread in the Palaearctic region. The subgenus Physematium is mostly found in the Americas and is characterised by bicolored scales on the rhizome. The third subgenus, Cheilanthopsis, is found in eastern Asia with the centre of diversity in the Himalayan region. The rhizome scales are concolorous, and the indusia are solid and globose rather than being composed of individual segments. In some cases in this subgenus, the sori are covered by 'false indusia', indusium-like structures that are formed from inrolled leaf margins rather than being independent membranes.

REFERENCES

Rothfels, C. J., M. A. Sundue, L.-Y. Kuo, A. Larsson, M. Kato, E. Schuettpelz & K. M. Pryer. 2012. A revised family-level classification for eupolypod II ferns (Polypodiidae: Polypodiales). Taxon 61 (3): 515–533.

Shao, Y., R. Wei, X. Zhang & Q. Xiang. 2015. Molecular phylogeny of the cliff ferns (Woodsiaceae: Polypodiales) with a proposed infrageneric classification. PLoS One 10 (9): e0136318.

The Solemyoida: A Taste for Sulphur

Atlantic awning clam Solemya velum, copyright Guus Roeselers.


The small bivalves that make up the Solemyoida were long a mystery, ecology-wise. Though they have a long history, potentially going back as far as the Ordovician (Cope 2000), they are not known to have ever been diverse, and only just over fifty species are known from the modern fauna. Living solemyoids are divided between two very distinct families that probably diverged near the origin of the group. The Solemyidae, awning clams, have relatively long shells that gape at each end, no teeth in the dorsal hinge, and tend to have an unusually thick periostracum (the overlying layer of horny proteinaceous matter that covers the outside of the mineral shell). They generally live in burrows buried deep in sediment. The Nucinellidae are a group of minute clams with an average length of about half a centimetre that are mostly found in deep waters, generally not buried quite so deep in the mud as the awning clams. They have a less elongate shell than the Solemyidae that does not gape and simple peg-like teeth in the hinge. What the two families do share is a markedly reduced gut and feeding appendages that initially caused much speculation about what exactly they were feeding on.

Nucinella sp. with foot extended, from Taylor & Glover (2010). Scale bar equals 1 mm.


The answer, as it turns out, was that they were not exactly 'feeding' on much, if anything. Solemyoids have relatively large gills that provide a comfortable living place for sulphur-oxidising bacteria, sheltered from the outside world while the host clam keeps up a continuous flow of water through its burrow from above the sediment surface. In return, the bacteria fix hydrogen sulphide rising from the underlying mud to provide both themselves and their host with nutrients. In this way, solemyoids have largely been able to get by without actively eating for close to 450 million years, achieving something the likes of Jasmuheen can only dream of.

REFERENCE

Cope, J. C. W. 2000. A new look at early bivalve phylogeny. In: Harper, E. M., J. D. Taylor & J. A. Crame (eds) The Evolutionary Biology of the Bivalvia pp. 81–95. The Geological Society: London.

The Ageniellini: Nest Evolution in Spider Wasps

The Pompilidae, commonly known as spider wasps or spider hawks, are a distinctive and often conspicuous group of wasps, well known for their practice of capturing spiders and sealing them paralysed into nest cells to serve as food for their developing larvae. Though spider hawks come in a wide range of sizes and colours, I can say from experience that they are often a challenging group of animals to work with taxonomically. Their superficial diversity often masks a certain structural sameness that makes it hard to develop a reliable system for the family. Nevertheless, one subgroup of the pompilids that has long been recognised as distinct is the subject of today's post, the Ageniellini.

Female Ageniella arcuata carrying a lynx spider, copyright Edward Trammel.


Agniellins are generally smaller spider wasps whose distinguishing features include a more or less constricted base to the metasoma, forming a petiole. Females have a collection of relatively long, forward-directed setae on the prementum, a sclerite on the underside of the head that forms the rear margin of the mouthparts (you could think of it as the wasp's 'chin'). As befits their smaller size, they provision their nests with smaller and medium-sized spiders. As well as paralysing the spider with their sting in the usual way, ageniellins will also often remove its legs before sealing it into a cell, though Barthélémy & Pitts (2012) observed that this might not be done with small spiders. The Ageniellini have been further divided between two subtribes, the Ageniellina and Auplopodina. In Ageniellina, the premental setae are relatively fine and the end of the metasomal dorsum (the pygidium) in females is rounded and hairy. In Auplopodina, the premental setae are further modified into strong, thick bristles and the female pygidium is more or less flattened and smooth. However, the aformentioned characters of Ageniellina are primitive and shared with non-ageniellin spider wasps. A phylogenetic analysis of the Ageniellini by Shimizu et al. (2010) reinforced the suggestion that 'Ageniellina' might be paraphyletic with regard to the monophyletic Auplopodina.

Auplopus carbonarius, copyright Fritz Geller-Grimm.


Ageniellini are of particular interest among spider wasps for the variety of nesting behaviours they exhibit, which were reviewed in detail by Evans & Shimizu (1996). The primitive nesting behaviour for pompilids, shared by species of 'Ageniellina', is to dig nest cells in holes in the ground. 'Ageniellina' construct short holes from pre-existing openings in the soil such as caves, crevices or the burrows of animals. The holes are closed by patting down soil using the end of the metasoma. The origin of the Auplopodina, however, saw a seemingly small innovation that was to have significant consequences: the evolution of the ability to carry a small amount of water in the crop. Initially, this allowed the wasps to nest in firmer ground than was previously possible, using water to soften the soil before digging. Many Auplopodina species still nest in this fashion. They could also carry balls of mud under the head using the basket of premental bristles, using the mud to close up holes. Eventually, they started using mud to build barrel-shaped nest cells above ground, bypassing the need to dig, and/or closing up suitable pre-existing cavities such as hollow plant stems or abandoned cells from other wasps. The most basic mud cells are still vulnerable to damage from rain and water so are built in sheltered locations such as attached to plant rootlets protruding from overhanging banks. However, some Auplopodina species have learnt to cover the outside of the cell with a coating of resin to provide water resistance and so are able to build in more exposed places such as underneath plant branches or leaves. Species of one genus, Poecilagenia, are kleptoparasites, breaking into the nests of other pompilids and closing them back up after depositing their own eggs inside.

Macromerella honesta females on a communal nest, from Barthélémy & Pitts (2012).


The greatest advance in nesting behaviour known from a handful of Auplopodina species is the appearance of communal behaviour, potentially derived from multiple factors. The need for suitable sheltered sites for nest-building places a premium on location, increasing the likelihood of intra-specific encounters. The ability to break down and re-purpose pre-existing nest cells rather than building entirely from scratch makes it worthwhile for females to linger around their own place of hatching. In one eastern Asian species, Machaerothrix tsushimensis, dominance behaviour has been observed around nests with one female largely monopolising cell construction and provisioning while other females remain largely inactive, only constructing their own cells when the dominant female is elsewhere. In other communal Auplopodina species, females will share in the construction and guarding of nest cells.

True eusocial behaviour as found in vespid wasps and bees is unknown in pompilids. It has been suggested that their practice of provisioning brood cells only at the time of the construction, without providing subsequent meals, may be a hindrance to sociability as there is little incentive for females to provide for the larvae of other individuals. Nevertheless, the Ageniellini demonstrate that basic communality is not beyond the abilities of spider wasps.

REFERENCES

Barthélémy, C., & J. Pitts. 2012. Observations on the nesting behavior of two agenielline spider wasps (Hymenoptera, Pompilidae) in Hong Kong, China: Macromerella honesta (Smith) and an Auplopus species. Journal of Hymenoptera Research 28: 13–35.

Evans, H. E., & A. Shimizu. 1996. The evolution of nest building and communal nesting in Ageniellini (Insecta: Hymenoptera: Pompilidae). Journal of Natural History 30 (11): 1633–1648.

Shimizu, A., M. Wasbauer & Y. Takami. 2010. Phylogeny and the evolution of nesting behaviour in the tribe Ageniellini (Insecta: Hymenoptera: Pompilidae). Zoological Journal of the Linnean Society 160: 88–117.

Ants in Bright Velvet

A paper that I've been intermittently working on for a while now finally saw publication last week. Authored by myself, Mark Murphy, Yvette Hitchen and Denis Brothers, the paper describes four new species of velvet ant from here in Western Australia.

Female Aglaotilla chalcea, photographed by yours truly.


Velvet ants are not actually ants but a distinct group of typically hairy wasps forming the family Mutillidae. They are strongly sexually dimorphic: females are wingless like ants but males have fully developed wings. They develop as kleptoparasites in the nests of other wasps, with the velvet ant larva feeding on the prey left to provision the host and/or on the host larva itself. Taxonomically, velvet ants are perhaps one of the more difficult wasp groups to work with. The high sexual dimorphism means that it is often impossible to match males with females unless one is lucky enough to catch them in the act of mating, and the mesosoma of females is highly sclerotised and fused with many of the characters useful for identifying other wasp groups no longer visible. The taxonomy of Australian velvet ants is particularly uncertain, almost to comical levels. A large number of species (possibly numbering in the hundreds) remain undescribed, and many of those species that have been described are yet not readily identifiable. No extensive survey of the Australian fauna has appeared since 1898 and most Australian species have been placed in a single genus Ephutomorpha. This genus was established by French entomologist Ernest André in 1902 with a definition that can basically be summarised as "Ugh, I can't even right now": it was explicitly intended as a dumping ground for Australian velvet ants that André was unable to sort more appropriately at the time. A vague promise to get onto it later never eventuated. Even at its time of establishment, Ephutomorpha included taxa that had already been designated as type species for genus names Bothriomutilla and Eurymutilla that should have taken precedence.

A few years ago, I was engaged in identifying wasp specimens collected by Mark Murphy as part of his research into pollinator ecology in the Western Australian wheatbelt. For those of you unfamiliar with the area, the Wheatbelt refers to a band of land inland from Perth. Most of the wheatbelt is rolling, semi-arid terrain that has been cleared for the growth of the eponymous wheat, with the indigenous forest largely reduced to isolated stands and reserves. Mark was studying the diversity of pollinator wasps in these remnant stands, most of which are dominated by wandoo Eucalyptus wandoo. As an example of the difficulties I was referring to above, I was able to recognise over two dozen morphospecies of velvet ants among specimens collected by Mark, only a couple of which I was able to even tentatively connect to known species. The specimens which formed the basis of the new publication came from a particular one of Mark's study methods, nest traps. Mark would leave wooden blocks into which holes had been drilled out in the field for a number of months, over which time they would hopefully be colonised by nesting wasps and bees (Mark was visiting traps once a month to check for nests). The holes were lined with paper tubes and if Mark found one that contained a nest, he would slide out the tube and take it back to the lab to be reared to maturity. Emerging wasps and bees were identified to species both by morphological examination and via the extraction of DNA for fingerprinting. Mark also found that he reared a number of parasitoids and kleptoparasites that were treated in the same way.

The male of Aglaotilla chalcea, also by yours truly.


I realised that this gave us an excellent opportunity regarding the mutillids, of which four identifiable species had emerged from Mark's nest samples. Because of Mark's rearing experiments, we had host data for all four species. Because of the use of DNA fingerprinting, we were able to identify both males and females of three of the four species (the fourth was recorded from a single nest that only provided us with female specimens). And at least two of the species appeared to be completely new to science. It didn't hurt that they were also all very attractive animals with brilliant metallic colours. So I prepared a manuscript describing all four species with myself, Mark and Yvette (who had done the DNA sequencing for the specimens) as authors and submitted it to the journal Zootaxa for consideration.

It was rejected.

That, as it turned out, was a good thing. One of the original reviewers was Denis Brothers of the University of KwaZulu-Natal, one of the world's leading authorities on velvet ants. Denis agreed that, while the paper couldn't stand as originally submitted, there was a definite value in what we were presenting. So he offered to help us with the composition. As well as correcting some misunderstandings I was guilty of regarding mutillid morphology (see my earlier comment on the difficulty of identifying features of the female mesosoma), Denis was able to confirm that all four of our species was actually new. He also informed us that they could be placed in a group of species that he had identified as part of as-yet unpublished research on Australian velvet ants and suggested that we establish a new genus for this group. This new genus was named Aglaotilla by Brothers (2018). Denis also added a new section to our manuscript summarising the recorded host data for Australian mutillids.

Aglaotilla species are mostly metallic in coloration, predominantly blue, green or purple (describing the colours of metallic wasps can be a challenge because the exact shade observed depends a lot on the incident lighting). One of our species, A. micra, has the mesosoma reddish with a purple gloss whereas an earlier described species A. discolor has the mesosoma entirely red. Females often have prominent spots or bands of clustered white hairs on the metasoma. Depending on the species, the colour pattern of the sexes may be similar or distinct. One of our new species, A. lathronymphos, has a species name that means 'secretly married' because without the DNA fingerprinting we would have had no reason to associate the bright blue males with the reddish-purple females. Females lack the rake-like spines on the fore legs and flattened plate at the end of the metasoma found in many other female mutillids. This almost certainly relates to their life cycle. Female velvet ants parasitising ground-nesting hosts use their fore legs to dig into the host nest and the terminal plate to tap down the ground after closing it back up. Aglaotilla females, where known, parasitise hosts that nest above ground in holes in trees and so do not need adaptations for digging. Three of the species we described, A. chalcea, A. lathronymphos and A. micra, were reared from the nests of crabronid wasps belonging to the genus Pison. The fourth species, A. schadophaga, was reared from the nests of resin bees. Aglaotilla species are very unusual among velvet ants in that more than one larva may grow to maturity in a single host nest cell; in all other mutillids for which host data is available, only a single individual will ever emerge from a single host.

A likely live female of Aglaotilla in search of a suitable host nest, copyright Mark A. Newton.


The Australian mutillid fauna includes a number of enticing taxa that deserve further examination: the strikingly patterned Australotilla species and the weird ant-associated Ponerotilla are just a couple of examples. Not to mention the hordes of new species that don't even have names yet. I have been pleased to make some contribution to this much-neglected family.

REFERENCES

André, E. 1902 Hymenoptera. Fam. Mutillidae. Genera Insectorum 11: 1–77, 3 pls.

Brothers, D. J. 2018. Aglaotilla, a new genus of Australian Mutillidae (Hymenoptera) with metallic coloration. Zootaxa 4415 (2): 357–368.

Taylor, C. K., M. V. Murphy, Y. Hitchen & D. J. Brothers. 2019. Four new species of Australian velvet ants (Hymenoptera: Mutillidae, Aglaotilla) reared from bee and wasp nests, with a review of Australian mutillid host records. Zootaxa 4609 (2): 201–224.

The Trechodini


The above figure, from Uéno (1990), shows Trechodes satoi, a fairly typical representative of the carabid ground beetle tribe Trechodini. Members of this tribe are found in many parts of the world, though they are absent from the Nearctic region and were unknown from northern Asia prior to the description of Eotrechodes larisae from the Russian Far East by Uéno et al. (1995). The greatest diversity of Trechodini is on the southern continents and most authors have accordingly assumed a Gondwanan origin for the lineage.

The Trechodini are a subgroup of the subfamily Trechinae (in the restricted sense; sometimes this grouping is reduced to a tribe in which case Trechodina is treated as a subtribe thereof). Trechines are a distinctive group of relatively small ground beetles, features of which include a head with well-developed frontal furrows extending from the front of the head to behind the eye, and two pairs of supra-orbital setae. Trechodini differ from other trechines in distinctive male genitalia in which the ejaculatory duct of the aedeagus is entirely exposed dorsally, the median lobe is open above and gutter-like, and there is no basal bulb. They also usually have three obtuse teeth near the base of the mandible though the South African genus Plocamotrechus is missing one of these teeth in the left mandible (Moore 1972).

Habitus of Canarobius oromii, from Machado (1992).


Despite being widespread, the distribution of Trechodini is patchy. They are generally restricted to damp habitats such as alongside streams and rivers. Among Australian species, Moore (1972) noted that the genera Trechodes and Paratrechodes were uniformly fully flighted whereas Trechobembix and Cyphotrechodes were often brachypterous. He suggested that this was connected to the last two genera being found in more stable habitats alongside standing water. A number of species in the tribe have moved into subterranean habitats such as caves and have reduced wings and eyes. In two genera found in lava caves on the Canary Islands, Canarobius and Spelaeovulcania, no trace of the eyes remains (Machado 1992). Considering the little-studied nature of such habitats around the world, it is possible that other trechodins remain to be discovered.
REFERENCES

Machado, A. 1992. Monografía de los Carábidos de las Islas Canarias (Insecta, Coleoptera). Instituto de Estudios Canarios: La Laguna.

Moore, B. P. 1972. A revision of the Australian Trechinae (Coleoptera: Carabidae). Australian Journal of Zoology, Supplementary Series 18: 1–61.

Uéno, S. 1990. A new Trechodes (Coleoptera, Trechinae) from near the northwestern corner of Thailand. Elytra 18 (1): 31–34.

Uéno, S., G. S. Lafer & Y. N. Sundukov. 1995. Discovery of a new trechodine (Coleoptera, Trechinae) in the Russian Far East. Elytra 23 (1): 109–117.

Metavononoides: Retreating from the Coast

I've commented before on the taxonomic issues bedevilling the study of South American harvestmen, particularly members of the diverse family Cosmetidae. Recent years have seen researchers make gradual but steady progress towards untangling these multifarious snarls by more firmly establishing the identities of this family's many genera.

Metavononoides guttulosus photographed by P. H. Martins, from Kury & Medrano (2018).


The genus Metavononoides was established by Roewer in 1928 for two species from south-eastern Brazil. As with other Roewerian genera, its definition was not exactly robust, being based on a combination of tarsal segment count together with the presence of a pair of large spines on the dorsal scutum. The genus was later re-defined by Kury (2003) who used it for a group of species found in the Brazilian Atlantic Forest region around Rio de Janeiro. Members of this group shared a number of distinctive features including the presence of a distinctive U-shaped marking (later dubbed a 'lyre mask' or 'lyra')on the scutum. A number of species previously placed in other genera were transferred to Metavononoides, and the next few years saw the description of a couple more species in the genus. And then Paecilaema happened.

The genus Paecilaema was first established by C. L. Koch in 1839 but a poor description of its type species P. u-flavum lead to confusion about its identity. Over time, Paecilaema became associated with a large number of species over a range stretching from Mexico to Brazil (as an aside, it doesn't help matters that Paecilaema has been one of those names that taxonomists have found themselves chronically uncertain how to spell). When Kury & Medrano (2018) recently set out to determine the exact identity of Paecilaema by determining that of its type, they fixed P. u-flavum as a species that was common around Rio de Janeiro and that corresponded to one of the species included by Kury (2003) in Metavononoides. As a result, many of the species shifted by Kury (2003) into Metavononoides were shifted once again into Paecilaema. Many of the species assigned to Paecilaema from outside the Atlantic Forest Region remain unrevised but will almost certainly prove to require re-classification.

Metavononoides barbacenensis photographed by P. H. Martins, from Kury & Medrano (2018).


Metavononoides was not outright synonymised with Paecilaema, though. Among the group of species possessing the aforementioned lyra on the scutum, Kury & Medrano (2018) identified two distinct subgroups. In one, corresponding to Paecilaema, the lyra is made up of two components. Part of the lyra is composed of light coloration on the plane of the scutum itself while another part is raised granules. In some species, these granules are particularly concentrated along the margins of the lyra (you can see an example on this on Flickr, photographed by Mario Jorge Martins; though labelled Metavononoides, this individual is now identifiable as Paecilaema u-flavum). In the second subgroup, corresponding to Metavononoides, the differentiated coloration on the plane of the scutum is absent and the lyra is composed solely of raised granules. Not only are the two genera morphologically distinct, they are also more or less geographically distinct. Whereas Paecilaema is found in the moist broadleaf forests closer to the coast, Metavononoides is now restricted to species largely found in the grasslands and shrublands further inland, corresponding to the Cerrado region. Though more depauperate of species than it was before, the identity of Metavononoides is certainly firmer.

REFERENCES

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1–337.

Kury, A. B., & M. Medrano. 2018. A whiter shade of pale: anchoring the name Paecilaema C. L. Koch, 1839 onto a neotype (Opiliones, Cosmetidae). Zootaxa 4521 (2): 191–219.

Roewer, C. F. 1928. Weitere Weberknechte II. II. Ergänzung der: "Weberknechte der Erde", 1923. Abhandlungen der Naturwissenschaftlichen Verein zu Bremen 26 (3): 527–632, 1 pl.

Strike up the Bandfish

The diversity of fishes can be absolutely overwhelming and, as a result, there a some distinctive groups that fail to get their time in the spotlight. For this post, I'm briefly highlighting one of the lesser-known fish families, the bandfishes of the Cepolidae.

Australian bandfish Cepola australis at home in its burrow, copyright Rudie H. Kuiter.


Cepolids are small fish (growing to about 40 cm at most with many species much smaller) that are widespread in the eastern Atlantic and the Indo-Pacific but nowhere common. They have a laterally compressed, tapering body and a lanceolate caudal (tail) fin. They have an angled mouth that is relatively large compared to their size and pelvic fins with a single spine and five segmented rays, four of which are branched (Smith-Vaniz 2001). Two subfamilies are recognised, the Cepolinae and Owstoniinae. The Cepolinae are particularly elongate in body form and have the dorsal and anal fins connected by membranes to the caudal fin; these three fins are all distinctly separate in the Owstoniinae. Cepolines are divided between two genera: Acanthocepola species have scaly cheeks and spines on the preopercular margin whereas Cepola have naked cheeks and no such spines. Classification of Owstoniinae has been a bit less settled. A recent revision of the subfamily recognised only a single genus Owstonia (Smith-Vaniz & Johnson 2016), synonymising the genus Sphenanthias previously distinguished by features of the lateral line. As an indication of how little-known cepolids are, Smith-Vaniz & Johnson's revision more than doubled the number of known species of owstoniine from fifteen to 36 .

Male Owstonia hawaiiensis, from Smith-Vaniz & Johnson (2016).


Cepolids are most commonly found in relatively deep water, up to about 475 m. They are not targeted by any significant fisheries though Wikipedia claims that the oldest known recipe from a named author is for the cooking of bandfish. Cepolinae live on sandy or muddy bottoms on continental shelves where they excavate burrows in which they insert themselves with the head protruding above the substrate. Owstonia species are free-swimming, more commonly found near rocky bottoms on upper slopes or around atolls. The diet, where known, appears to be composed of zooplankton though Smith-Vaniz & Johnson (2016) suggested on the basis of tooth morphology that Owstonia were detritivores for at least part of their life cycle.

REFERENCES

Smith-Vaniz, W. F. 2001. Cepolidae. Bandfishes. In: Carpenter, K. E., & V. H. Niem (eds) FAO Species Identification Guide for Fishery Purposes. The Living Marine Resources of the Western Central Pacific vol. 5. Bony fishes part 3 (Menidae to Pomacentridae) pp. 3331–3332. Food and Agriculture Organization of the United Nations: Rome.

Smith-Vaniz, W. F., & G. D. Johnson. 2016. Hidden diversity in deep-water bandfishes: review of Owstonia with descriptions of twenty-one new species (Teleostei: Cepolidae: Owstoniinae). Zootaxa 4187 (1): 1–103.

Goldenrod

Growing up as a child in rural New Zealand, I remember the community social events that would sometimes be held at the local district hall. On one evening, if I recall correctly, the event being held was a quiz night modelled after then-popular game show It's in the Bag. For those unfamiliar with this long-running institution, contestants on the show who successfully answered a series of general knowledge questions asked by Selwyn Toogood, a large avuncular man with an appropriately fruity voice, would be offered the choice between a cash prize up front or a 'bag' containing an unknown prize. This prize could potentially be something worth a lot more than the money on offer, such as a trip away or a home appliance (game shows in the 1980s often included whiteware among their top tier prizes). On the other hand, it could be worth a lot less, potentially even being effectively worthless (as viewers at home, of course, we always hoped for the latter). On this occasion, one of the 'prizes' on offer was a packet of seeds from 'the pretty yellow flowers that grow so vigorously in the region'. Everyone in the audience would instantly recognise the flowers in question as ragwort Senecio jacobaea, a pernicious weed much maligned due to its toxicity to livestock. Ragwort probably arrived in New Zealand as a contaminant in grass seed, but for today's post, I'm looking at another member of the daisy family which became a weed after being more deliberately spread around.

Tall goldenrod Solidago gigantea, copyright Pethan.


Solidago, the goldenrods, is a genus of perennial herbs with a woody caudex or rhizome and usually bright yellow flowers. About 100 to 120 species are currently recognised in the genus, the great majority of which are native to North America. Other species are found in South America and Eurasia, and a number of the North American species have been spread around the world by human activity. The number of species to be recognised is somewhat disputed because, as with many decent-sized plant genera, goldenrods have a tendency to laugh in the face in clear species concepts. Differences between species can be difficult to observe and hybrids are not uncommon. Individuals belonging to the same species may vary notably with geography and growth conditions and determining whether variation is genetic or environmental has historically required extensive growth experiments cultivating seed collections at varying locations. Vegetative spreading through rhizomes may lead to isolated populations of near-clonal individuals that may come to be recognised as 'microspecies'. As a result, what one author may recognise as a number of distinct species may be treated by another author as variants of a single species. For example, a study of altitudinal variants of the European S. virgaurea in Poland by Kiełtyk & Mirek (2014) lead them to recognise two species that had previously been confused, the lowland S. virgaurea and the montane S. minuta. The two were best distinguished by relatively fine-scale features of the flower heads, most notably the number of tubular florets in each head.

Canada goldenrod Solidago canadensis, copyright Olivier Pichard.


In a review of the North American Solidago species, Semple & Cook (2006) divided the genus between two sections. The smaller section Ptarmicoidei, including only half a dozen species, is characterised by clustering of flower heads in flat-topped arrays. The remaining species in the much larger section Solidago may have heads in rounded, conical or club-shaped arrays, or bear flower heads in axillary clusters. The distinctiveness of section Ptarmicoidei is enough that some authors have placed it as a separate genus Oligoneuron. Research is ongoing concerning the phylogeny of Solidago and its precise relationships with related genera.

Historically, the European Solidago virgaurea was valued for its supposed medicinal qualities (hence the genus name, which can be translated as 'becoming whole'). But while the dried flowers may still be used in making herbal tea, goldenrod does not seem to be currently regarded as of much pharmaceutical significance. As long ago as 1597, John Gerard noted in his Herball that the once highly prized herb had plummeted in value and regard once it was found to be growing wild in England, making it a mere local weed instead of an exotic import*. In the 1920s, Thomas Edison experimented with using goldenrod as a source of rubber. Investigations in this line were later continued in the 1940s by agrarian scientist George Washington Carver (under the patronage of Henry Ford), partially to counter rubber shortages during World War II. However, rubber yield from goldenrod is low and the rubber produced of low quality, so it never became a commercially significant source.

*'...in my remembrance, I haue known the dried herbe which came from beyond the ſea ſold in Bucklersbury in London for halfe a crowne an ounce. But ſince it was found in Hampſtead wood, euen as it were at our townes end, no man will giue halfe a crowne for an hundred weight of it: which plainely ſetteth forth our inconſtancie and ſudden mutabilitie, eſteeming no longer of any thing, how pretious ſoeuer it be, than whileſt it is ſtrange and rare. This verifieth our Engliſh proverbe, Far fetcht and deare bought is beſt for Ladies.'

Woundwort Solidago virgaurea var. leiocarpa, copyright Alpsdrake.


As alluded to above, a number of North American goldenrod species have been carried to temperate regions around the world as ornamentals or to provide nectar for bees. Unfortunately, some of these species have become significant invasive weeds in their adopted homes. Canada goldenrod Solidago canadensis can have an allelopathic effect on surrounding vegetation, producing water-soluble compounds that may inhibit the germination and growth of seeds (Werner et al. 1980). It may also act as a reservoir for pathogens of crop plants. Goldenrod is also commonly accused of causing hay fever but, in this regard at least, it seems to be largely innocent. Goldenrod plants shed relatively little pollen; as the flowers are insect-pollinated, the pollen is relatively unlikely to enter the air column. Instead, it seems that the conspicuous goldenrod flowers are blamed for the more copious pollen shed by less visible plants such as ragweeds flowering at the same time.

REFERENCES

Kiełtyk, P., & Z. Mirek. 2014. Taxonomy of the Solidago virgaurea group (Asteraceae) in Poland, with special reference to variability along an altitudinal gradient. Folia Geobotanica 49: 259–282.

Semple, J. C., & R. E. Cook. 2006. Solidago Linnaeus. In: Flora of North America Editorial Committee (eds) Flora of North America vol. 20. Asteraceae, part 2. Astereae and Senecioneae pp. 107–166. Oxford University Press: New York.

Werner, P. A., I. K. Bradbury & R. S. Gross. 1980. The biology of Canadian weeds. 45. Solidago canadensis L. Canadian Journal of Plant Science 60: 1393–1409.

Of Crosses and Clubs

One of the major groups of eukaryotes that has been somewhat under-represented on this site has been the Cercozoa. This is a diverse clade of unicellular organisms, distantly related to the foraminiferans and radiolarians, that has only been recognised within the last few decades with the introduction of molecular phylogenetic analyses. It has become increasingly clear that cercozoans form a major part of the world's microscopic biota but this diversity is poorly known as most cercozoans have little direct effect on human industry. One subgroup of the cercozoans that does make itself known in this regard, however, is the Phytomyxea.

Club roots of a rape plant infected by Plasmodiophora brassicae, photographed by Leafhopper65.


The Phytomyxea include parasites of plants, algae and other aquatic micro-organisms. The best known phytomyxean species, Plasmodiophora brassicae, causes a condition known as 'club root' in cabbages; another, Spongospora subterranea, is responsible for powdery scab on potatoes. They form multinucleate 'plasmodia' when growing within the cells of their host. Nuclei divide within the plasmodium in a characteristic cruciform pattern: the nucleolus does not break down during division but instead stretches elongately before pinching in two. While stretched, the nucleolus is oriented perpendicularly to the separating chromatin, forming a cross (Dylewski 1990). Owing to a superficial resemblance between phytomyxean plasmodia and those formed by the plasmodial slime moulds, phytomyxeans were historically also treated as slime moulds and hence as fungi (alternative historical names for the group, such as Plasmodiophoromycota or Plasmodiophoromycetes, reflect this supposed affinity). However, whereas the amoeboid plasmodia of slime moulds are capable of active movement and ingestion of food particles via phagocytosis, the phytomyxean plasmodium is more or less incapable of moving of its own volition, instead moving within the host cell by means of the host's own cytoplasmic streaming, and do not engulf host tissue in vacuoles. Slime moulds are no longer regarded as a single evolutionary lineage, and no 'slime moulds' are directly related to fungi.

Nuclei undergoing cruciform division in plasmodium of Tetramyxa parasitica, copyright James P. Braselton.


Over 40 species of Phytomyxea have been recognised to date but, not surprisingly, studies on the group have focused heavily on those species of economic importance to humans (Neuhauser et al. 2011). Terrestrial phytomyxeans produce thick-walled resting cysts, often aggregated in clumps known as cystosori, that may persist in soil for several years. These cysts hatch into biflagellate primary zoospores that seek out a suitable host. Upon finding one, the spore ceases swimming and adheres to the host cell before piercing the cell wall and injecting its cytoplasm which grows into the aforementioned plasmodium. Nuclei divide by mitosis and are eventually parcelled into sporangia that release secondary zoospores that escape from the host cell. These secondary spores generally do not disperse far; instead, they tend to cycle back and re-infect the original host to form new plasmodia. When these secondary plasmodia reach maturity, their nuclei divide meiotically and are divvied into new resting cysts. Presumably, the haploid nuclei produced in this manner fuse at some point with another to return to diploidy but it is unknown when exactly this happens. The cysts, when formed, each contain two nuclei but later only one, so it is possible that this reduction results from fusion. However, it might seem more likely that one of the nuclei breaks down without issue and the cyst remains haploid through to excystment with fusion occurring at the primary zoospore phase, thus allowing greater scope for cross-fertilisation. Marine phytomyxeans have long been thought not to produce resting cysts but recent observations of variations in zoospore morphology and sporangial wall thickness in the brown algal parasite Maullinia ectocarpii suggest the possibility of similarly complex life cycles (Neuhauser et al. 2011). The length of the phytomyxean life cycle can vary from about a month for Plasmodiophora brassicae to as little as one or two days for the brown algal parasite Phagomyxa algarum.

Diagram of the life cycle of Plasmodiophora brassicae, from Auer & Ludwig-Müller (2015).


For most phytomyxean species, infection by plasmodia causes physiological changes in the host, commonly taking the form of galls or other excesses of growth. Club root disease of Brassica results from Plasmodiophora brassicae plasmodia producing growth hormones that cause nutrients to be concentrated in the roots at the expense of leaf growth, thus increasing their availability to the parasite. Other alterations may be related to parasite dispersal. Ligniera junci, a parasite of rushes, causes a proliferation in the growth of root hairs in which the resting cysts form, providing an extra protective sheath. Plasmodiophora bicaudata is a parasite of marine Zostera eelgrass that produces galls at internodes together with reduced root growth. As a result, the eelgrass is easily uprooted by water movement, potentially being carried to new areas where the next generation of phytomyxeans can find new eelgrasses to infect.

REFERENCES

Dylewski, D. P. 1990. Phylum Plasmodiophoromycota. In: Margulis, L., J. O. Corliss, M. Melkonian & D. J. Chapman (eds) Handbook of Protoctista. The structure, cultivation, habitats and life histories of the eukaryotic microorganisms and their descendants exclusive of animals, plants and fungi. A guide to the algae, ciliates, foraminifera, sporozoa, water molds, slime molds and the other protoctists pp. 399–416. Jones & Bartlett Publishers: Boston.

Neuhauser, S., M. Kirchmair & F. H. Gleason. 2011. The ecological potentials of Phytomyxea ("plasmodiophorids") in aquatic food webs. Hydrobiologia 659: 23–35.

Ice-cream Cones of the Early Palaeozoic

It's time for something I haven't done in a very long time... (credit to Niel from Microecos):


I briefly described tentaculitoids on this site way back in September 2007. These narrowly conical shells of uncertain affinities were prominent members of the marine fauna during the Silurian and the Devonian, only to then disappear without a trace. No direct evidence is available for the soft-body appearance of the animals that produced them nor are we overly certain on their lifestyle. But at least one of the major subgroups of the tentaculitoids, the Dacryoconarida, are held to be of palaeontological significance due to their ubiquity and cosmopolitan distribution at the species level making them of use in biostratigraphy.

Reconstruction of Nowakia elegans, from Berkyová et al. (2007).


Dacryoconarids have generally been presumed to be planktonic in some way, owing to the aforementioned tendency of individual species to be found more or less worldwide, together with their small size (generally about the centimetre range). Dacryoconarids are distinguished from other tentaculitoids by the apical portion of their shell ending in a small globular bulb, presumed to represent the embryonic or larval shell of the original animal (Farsan 2005). A more or less distinct constriction or 'neck' separates this embryonic bulb from the remainder of the shell. In those forms with more heavily ornamented shells such as the genus Nowakia, a distinct juvenile section of the shell is visible immediately following the embryonic bulb in which the adult ornament is absent or weakly developed; said adult ornament, when it appears, takes the form of rounded transverse ridges and troughs, often associated with longitudinal and/or transverse striae. In other forms, such as the genus Styliolina, the outside of the shell is flat and ridgeless, with at most the only ornamentation present being striae. The inside of the shell may be rippled to follow the exterior ornamentation or it may be perfectly smooth (Fisher 1962).

Dacryoconarids are first recorded from the Late Ordovician but they remained at relatively low diversity until the Devonian which saw a notable radiation (Wittmer & Miller 2011). Nevertheless, they declined rapidly towards the end of the Devonian. It has been suggested that their extinction by the end of that period may be related to the appearance of more actively swimming predatory fish before which the tentaculitoids may have been relatively defenceless. Other early Palaeozoic planktic groups such as the graptoloids experienced a similar collapse at about this time, though the disappearance of the dacryoconarids may have lagged behind that of the graptoloids.

Styliolina clavulus, from Fisher (1962).


Over the years, a wide range of suggestions have been made about the affinities of the tentaculitoids, ranging from jellyfish to annelids. Perhaps the most persistent association has been made with molluscs but there really is little to support such a premise than the possession of a calcareous shell, a feature that is hardly unique to molluscs even among living animals. The structure of the tentaculitoid shell is most similar to that of some brachiopods (Fisher 1962) and some sort of brachiozoan affinity is perhaps the currently most favoured concept. As noted above, we know nothing about the tentaculitoid anatomy other than what we can infer from the nature of the shells themselves. In some larger tentaculitoids (though not among the dacryoconarids so far as we know) the apical parts of the shell may become walled off by solid septa so the living animal presumably didn't occupy the entire shell. Fisher (1962) described the tentaculitoids as "presumably tentacle-bearing" but I have no idea on what basis he made that statement (as I've noted before, the name 'tentaculitoid' itself comes not from a belief that they possess tentacles but from the mistaken interpretation of the first specimens named as being themselves the tentacles of larger animal). Tentacles would be a not unreasonable method of capturing the smaller micro-plankton on which the dacryoconarids presumably fed but it is not impossible that some other structure served this purpose.

REFERENCES

Farsan, N. M. 2005. Description of the early ontogenetic part of the tentaculitids, with implications for classification. Lethaia 38: 255–270.

Fisher, D. W. 1962. Small conoidal shells of uncertain affinities. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W98–W143. Geological Society of America, and University of Kansas Press.

Wittmer, J. M., & A. I. Miller. 2011. Dissecting the global diversity trajectory of an enigmatic group: the paleogeographic history of tentaculitoids. Palaeogeography, Palaeoclimatology, Palaeoecology 312: 54–65.

Flies on Stilts

Flies deserve a much better rep than they're usually given. They are animals of grace and poise that step lightly through the world. And perhaps few flies have an appearance that conveys that grace better than the stilt-legged flies of the Micropezidae. For today's post, I wanted to look at one particular subfamily of micropezids, the Taeniapterinae.

Scipopus sp., copyright Gail Hampshire.


Stilt-legged flies are found in most parts of the world but are particularly diverse in tropical regions. As their name indicates, they are light-bodied flies with notably long legs, the middle and hind legs being much longer than the fore legs. This legginess perhaps reaches its peak in the Madagascan genus Stiltissima, males of which have the hind femora alone at least 2.5 times the length of their thorax (Barraclough 1991). The adults are predators of small insects but are also attracted to decaying fruit or dung. Larvae of the family are little known but indications are that they feed on the aforementioned ordure or other rotting vegetation. Many of them are mimics of wasps such as ichneumons or ants with their slender figure resembling the narrow-waisted appearance of a wasp. Because micropezids belong to the brachyceran lineage of flies, in which the antennae are few-segmented and usually short, the front pair of legs is instead held out in front to imitate the wasp's antennae.

Habitus of Stiltissima violacea, from Barraclough (1991).


The Taeniapterinae are the most diverse of three subfamilies recognised within the Micropezidae. Distinctive features of this subfamily include ocelli sitting relatively forward on the top of the head, a dense vertical fan of bristles on the sternopleuron (the sclerite on the side of the thorax just between the base of the fore and middle legs) and a vestigial subscutellum (Jackson et al. 2015). Though cosmopolitan in distribution, and the only micropezid subfamily known from sub-Saharan Africa (Barraclough 1991; the only non-taeniapterines known from the Afrotropical region are restricted to the Mascarene islands), taeniapterines are most diverse in the Neotropical region.

Mesoconius dianthus contrasted with its ichneumon model Cryptopteryx, from Marshall (2015).


The Taeniapterinae have been divided into two tribes based on the length of the cup cell near the base of the fore wing, the short-celled Rainieriini and the long-celled Taeniapterini (Jackson et al. 2015). All taeniapterines found outside the Neotropical region belong to the Rainieriini, as well as a number of Neotropical genera. The Taeniapterini are restricted to the New World. Genera of Taeniapterinae are often poorly distinguished with the relationships between species obscured by the evolution of features related to mimicking their wasp models. A phylogenetic analysis of selected Taeniapterinae by Jackson et al. (2015) indicated many recognised genera were non-monophyletic. It also cast doubt on the tribal classification with the Taeniapterini rendering the Rainieriini paraphyletic.

REFERENCES

Barraclough, D. A. 1991. Review of the Madagascan Taeniapterinae (Diptera: Micropezidae), with the description of a remarkably elongate-legged new genus and first record of Rainieria Rondani from the subregion. Annals of the Natal Museum 32: 1–11.

Jackson, M. D., S. A. Marshall & J. H. Skevington. 2015. Molecular phylogeny of the Taeniapterini (Diptera: Micropezidae) using nuclear and mitochondrial DNA, with a reclassification of the genus Taeniaptera Macquart. Insect Systematics and Evolution 46: 411–430.