Field of Science

Sweepers

It's time to meet the sweepers.

Smallscale bullseyes Pempheris compressa, copyright John Turnbull.


Sweepers, Pempheridae, are a group of moderately sized marine fish (usually about fifteen to twenty centimetres in length) found around tropical reefs in the Indo-Pacific and western Atlantic. I don't know why they're called sweepers, but in some areas they may be among the most abundant fish on the reef. Distinctive features of the group include a short, high dorsal fin and a long anal fin. The lateral line is also distinctively long, extending past the end of the tail right onto the caudal fin. Perhaps the feature that most stands out about sweepers is their large eyes. The eyes are so big because sweepers are nocturnal; during the day they retreat into protected crevices and caves, emerging at night to feed on minute crustaceans and other small animals (Mooi 2001).

Pygmy sweeper Parapriacanthus ransonneti, from here.


Sweepers are divided between two quite distinct genera. Members of the genus Parapriacanthus have a more 'average fish-like' elongate profile with the body less deep than the head is long. The other genus, Pempheris, has a distinctively deep profile, deeper than the head is long. The exact number of species of pempherid appears to still be uncertain. Pempherids lack the striking markings of other tropical fish and species can appear very similar to each other. What is more, they have two layers of scales on the body, with the outer scales being larger than the inner and deciduous (easily shed), and loss of the outer scales has the potential to change an individual's superficial appearance. Early descriptions of pempherid species are often inadequate for their reliable identification, and new species continue to be described at a quite rapid pace. A recent publication by Randall & Victor (2015), for instance, described no less than thirty-four new species of Pempheris from various locations in the Indian Ocean, close to doubling the number of species in the genus at a stroke. The genus Parapriacanthus is much less diverse, with only about five recognised species.

Orange-striped bullseyes Pempheris ornata in hiding during the day, copyright Peter Southwood.


Because of their relatively small size and retiring habits, sweepers are mostly not that significant economically. At least one species, Pempheris xanthoptera, is fished off the coast of Japan and mostly eaten as fish paste; it is supposed to be quite tasty. Some have appeared in aquaria.

When foraging at night, sweepers communicate with each other by producing popping noises through muscular flexing of the swim bladder wall. Noise production increases in the presence of potential threats, perhaps to warn other members of the school. At least some pempherid species also have bioluminescent glands associated with the posterior part of the gut. The bioluminescent compound is not directly produced by the fish itself but obtained by consuming bioluminescent ostracods. I haven't found whether the function of this bioluminescence is specifically known for pempherids, but similar ventral glows in other fish provide camouflage by breaking up the fish's silhouette when seen from below.

REFERENCES

Mooi, R. D. 2001. Pempheridae. Sweepers (bullseyes). FAO Species Identification Guide for Fishery Purposes. The Living Resources of the Western Central Pacific vol. 5. Bony fishes part 3 (Menidae to Pomacentridae) pp. 3201–3204. Food and Agriculture Organization of the United Nations: Rome.

Randall, J. E., & B. C. Victor. 2015. Descriptions of thirty-four new species of the fish genus Pempheris (Perciformes: Pempheridae), with a key to the species of the western Indian Ocean. Journal of the Ocean Science Foundation 18: 77 pp.

Long-legged Harvestmen of Southern Africa

New paper time!

Rhampsinitus conjunctidens, a new species of harvestmen from north-east South Africa, from Taylor (2017).


Taylor, C. K. 2017. Notes on Phalangiidae (Arachnida: Opiliones) of southern Africa with description of new species and comments on within-species variation. Zootaxa 4272 (2): 236–250.

When I first started research for my PhD thesis, *cough* years ago, I asked a number of museums if they could loan me their collections of monoscutid (now neopilionid) harvestmen. The species that I was interested in are found in Australia and New Zealand but when I opened a package of specimens sent to me from the California Academy of Sciences, I found a number of specimens from Africa in the mix. I immediately recognised what they were: not neopilionids, but representatives of another harvestment family, the Phalangiidae.

It seemed an easy enough error to make. Many species of southern African Phalangiidae resemble a lot of neopilionids in that the males have over-sized, elongate chelicerae. I referred to some of these species in the genus Rhampsinitus in an earlier post. To those not familiar with harvestmen diversity (which, let's face it, is the majority of people out there), the two groups can look very similar. True, the phalangiids are all distinctly much spikier than the neopilionids, but that doesn't seem that major a difference. To really see where they diverge from each other, you need to reach underneath the males' genital opercula and pull out their todgers.

Anywho, the specimens sat in storage for much longer than they should have, until I finally got around to looking them over in the latter part of last year. I then decided that it was worth writing them up into a short paper. Not only was there at least one new species among the specimens, they told me some very interesting things about variation within the species. Not only do Rhampsinitus species resemble Australasian neopilionids in their enlarged chelicerae, they resemble them in that individuals of a species vary in how enlarged the chelicerae are.

Major (left) and minor males of Rhampsinitus nubicolus, from Taylor (2013).


Now, I was not the first person to observe this point. Axel Schönhofer (2008) had already provided some detailed examples of variation in males of Rhampsinitus cf. leighi. I did, however, observe that the variation was even greater than Axel seemed to have recognised. Some of the least developed males of the species I was looking at had chelicerae that were pretty much no more developed than those of females. In some ways, the variation was even more remarkable than what I was familiar with in neopilionids. In most of the latter, major and minor males tend to be pretty similar to each other in features other than cheliceral development. In Rhampsinitus, we can see variation in almost all the features related to sexual dimorphism. In the species pictured immediately above, R. nubicolus, major males have massively long pedipalps as well as the long chelicerae; minor males have short, stubby pedipalps like those of a female. We can tell that they are the same species because they are found in the same location and have matching genitalia, but on the outside you would be hard pressed to pick them as such. Just to confuse matters even more, major males of two species may look very different to each other whereas minor males are externally almost identical. Without looking at the genitalia, it is all but impossible to identify which species a minor male belongs to.

As with the neopilionids, we can't yet say for sure what this variation means for the species' behaviour. In many other animal species with comparably varying males, large males will fight to protect and contain females while small males adopt a sneaking behaviour and try to spot females that are not being watched by large males. It seems quite possible that a similar thing is going on with Rhampsinitus. If you're a keen natural historian or behavioralist, there's something here that is crying to be looked into.

REFERENCE

Schönhofer, A. L. 2008. On harvestmen from the Soutpansberg, South Africa, with description of a new species of Monomontia (Arachnida: Opiliones). African Invertebrates 49 (2): 109–126.

A Mystery Ammonoid

Münster's (1834) figure of Goniatites hybridus.


Looks like I drew another dud. For today;s semi-random post, I ended up tasking myself to write something about the Devonian ammonoid genus Heminautilinus. But as it turns out, there simply isn't that much to say about this genus, and what there is isn't really worth saying.

Heminautilinus was established as a genus by A. Hyatt in 1884. He diagnosed it as including "species with whorls similar to those of Anarcestes, but with angular lateral lobes in the adults", and designated George de Münster's (1834) Goniatites hybridus as type species on the basis of that author's original figure. The problem is that Münster's figure is apparently not very reliable; the original specimen was only fragmentary and Münster himself expressed uncertainty as to just what section of the ammonoid conch he had on hand. So Hyatt's assumption that Münster's species retained some juvenile features to maturity should not be considered reliable.

As a result, Hyatt's genus seems to have been pretty roundly ignored. Those authors who have made some speculation as to its identity have suggested that it is probably synonymous with some better known genus such as Cheiloceras or Imitoceras. This might present something of an issue because either one of these genera was published more recently than 1884, meaning that Heminautilinus should be considered the senior name. Because there would be little to be gained from replacing a familiar name with one that is all but forgotten, it seems most likely that, even if Heminautilinus' identity could be reliably established, it would be somehow suppressed. As such, Heminautilinus seems doomed to remain in obscurity.

REFERENCES

Hyatt, A. 1883–1884. Genera of fossil cephalopods. Boston Soc. Nat. History, Proc. 22: 253–338.

Münster, G. de. 1834. Mémoire sur les clymènes et les goniatites du calcaire de transition du Fichtelgebirge Annales des Sciences Naturelles, seconde série, Zoologie 1: 65–99, pls 1–6.

Blue Moon

Male blue moon butterfly Hypolimnas bolina, photographed by Comacontrol.


My native country of New Zealand is not home to a large diversity of butterflies. Only a couple of dozen or so species are known from the entire country. It would not be unreasonable for a keen butterfly spotter to attempt to track down them all. But one particular species of butterfly generally included in New Zealand lists would a touch of luck: the aptly named blue moon Hypolimnas bolina.

This is because the blue moon is not a regular resident of New Zealand (I've personally never spotted one). It is native to a wide region stretching from Madagascar and India to Japan and northern Australasia where it is usually referred to by the more prosaic name of common or greater eggfly. The only examples found in New Zealand are vagrants who lost their way on southwards migrations. Nevertheless, such vagrants are regular enough for its local appellation to be thought worth coining. Not only does it reflect their rarity, it also describes the appearance of the male, with the wings bearing blue-ringed white spots on a black background.

Two females of Hypolimnas bolina. On the left, a mimetic individual, copyright Greg Hume; on the right, a non-mimetic individual, copyright W. A. Djatmiko.


The appearance of the female is a bit harder to explain because it can vary between individuals. Females of the eggfly genus Hypolimnas are commonly mimics of other, poisonous butterflies of the subfamily Danainae, to which eggflies are only distantly related (both groups belong to the family Nymphalidae but eggflies are placed in the subfamily Nymphalinae). For instance, the diadem or danaid eggfly H. misippus of Africa and Asia (and also introduced into parts of the Americas adjoining the Caribbean) is a mimic of the plain tiger Danaus chrysippus. The chosen model of H. bolina in the western part of its range is the common crow Euploea core and in the region of India almost all females are a remarkably good copy of that species (above left). But as one moves east, one starts seeing females of H. bolina that are not mimics like the individual shown above right; by the time one reaches Australia these make up the greater part of the population. Mimetic females may also vary to resemble different Euploea species, depending on which model is locally present.

Female danaid eggfly Hypolimnas misippus, copyright Raju Kasambe. Males of this species are similar to those of H. bolina but lack the blue rings around the white spots on the wings.

There are about two dozen species of Hypolimnas eggflies found in various parts of the Old World tropics. Hypolimnas misippus is also found in parts of the Americas around the Caribbean where its presence is usually explained as the result of an early introduction (possibly, and somewhat poignantly, in connection to the slave trade). Their vernacular name is probably derived from the unique behaviour (for butterflies) of a number of species whose females stand guard over their eggs, beating their wings over them to protect them from predators until hatching. About two-thirds of Hypolimnas species are mimics. In some of these species, both sexes are mimetic; others resemble H. bolina and H. misippus in that only the females are mimics (Vane-Wright et al. 1977). One might be tempted to ask why this variation exists. One point to be considered is that there are limits on when mimicry is likely to be effective. The mimic needs to be much less abundant than its model, otherwise potential predators may not learn to associate the distinctive coloration with the toxic original. Swinhoe (1896) noted that males of Hypolimnas misippus were very active, aggressively defending their territories from other butterflies, and suggested that this agility might provide males with alternative defences to mimicry. The more sedentary females (especially when egg-guarding) might be expected to benefit more from the passive protection mimicry provides, but mimesis might be expected to disappear in areas where their model is less abundant.

REFERENCES

Swinhoe, C. 1896. On mimicry in butterflies of the genus Hypolimnas. Journal of the Linnean Society, Zoology 25: 339–348.

Vane-Wright, R. I., P. R. Ackery & R. L. Smiles. 1977. The polymorphism, mimicry, and host plant relationships of Hypolimnas butterflies. Zoological Journal of the Linnean Society 9: 285–297.

False Spider Mites

Among the enormous diversity of the world's mites, some families are particularly notorious for the damage that they inflict on commercial plant crops. Among such Acari non grata are the spider mites of the family Tetranychidae or the gall mites of the Eriophyidae. But a third, equally notorious group is the false spider mites or flat mites of the Tenuipalpidae.

Red and black flat mite Brevipalpus phoenicis, false-colour SEM by Christopher Pooley.


False spider mites include about 800 known species of more or less flattened, slow-moving mites. They are closely related to the true spider mites and both families have the chelicerae modified into a pair of long, whip-like retractable stylets that are used to pierce and suck fluids from plant tissues. In the case of the false spider mites, though, their commercial infamy comes not only from the direct damage caused by the feeding mites themselves but also from the effects of transmitted viruses. Viruses transmitted by false spider mites include the causative agents of diseases such as citrus leprosis and coffee ring spot and may cause significant reductions in the yield and lifespan of infected plants.

Morphologically, false spider mites differ from true spider mites in the absence of what is called the 'thumb-claw' process, an arrangement of the tarsus of the pedipalp alongside a claw on the seta (hence the family name which means 'slender palp'). The palps are often reduced, with some species having only the barest remnant. Some species also show reduction in the fourth pair of legs, and females of a number of species are six-legged as adults. This merely stands as another example of how mite morphology functions purely to play silly buggers with anything one might learn in basic animal biology.

Hebe stem gall mites Dolichotetranychus ancistrus inside an open gall, copyright Plant and Food Research.


Parthenogenesis is also common in false spider mites. Species found in cooler climes will often overwinter as females, with a new generation of males not appearing until the next spring. In some species, eggs produced parthenogenetically will hatch into males; in others, they will produce females. A few species almost entirely lack functional males. A small group of these species in the genus Brevipalpus is unique among animals in being both parthenogenetic and genetically haploid.

Almost all forms of seed plant seem to be vulnerable to some form of flat mite or another; some mite species are very catholic in their tastes and will latch onto almost anything green and photosynthesising. Others are more discerning. How false spider mites make their way from one host plant to another is little known but they may be passively carried through the air on the wind. Alternatively, they may be inadvertently carried from place to place by feeding herbivores, or by the very human horticulturalists that suffer so much from their presence.

REFERENCE

Walter, D. E., E. E. Lindquist, I. M. Smith, D. R. Cook & G. W. Krantz. 2009. Order Trombidiformes. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 233-420. Texas Tech University Press.

Oily and Salty Trees

The Annonaceae is another one of those plant families like Acanthaceae that, despite containing a high diversity of speceis, tend to be overlooked because that diversity is mostly tropical. A number of species in the type genus Annona produce commercially significant fruits: custard apples, cherimoyas, soursops and the like. However, these are just a few of the 2400+ species of trees and lianes assigned to this family.

Ylang-ylang flowers Cananga odorata, from here.


Taxonomically, the Annonaceae is well established as distinct, readily recognised by a number of distinctive features. Among these is a characteristic 'cobweb' appearance to the wood structure when seen in cross-section, resulting from prominent rays of xylem connected by narrow cross-bands of parenchyma (Chatrou et al. 2012). Relationships within the family have been much harder to work out, not becoming well established until the advent of the molecular era. Recently, Chatrou et al. (2012) have recognised four subfamilies within the Annonaceae. The majority of species are placed in the subfamilies Annonoideae and Malmeoideae (which together form a clade), but a handful of species are placed in two basal subfamilies: one for the single genus Anaxagorea, and the Ambavioideae. Anaxagorea and the ambavioids differ from the annonoid-malmeoid clade in the structure of their seeds. Seeds of Annonaceae have what is called ruminate endosperm: that is, the surface of the endosperm is not smooth, but divided by wrinkles and grooves (the term 'ruminate' literally means 'chewed'). In Annonoideae and Malmeoideae, the ruminations of the endosperm are shaped like spines or lamellae. In Anaxagorea and the Ambavioideae, the ruminations are irregular in appearance. Molecular analyses place Anaxagorea as the sister taxon to all other Annonaceae.

View into the canopy of a salt-and-oil tree Cleistopholis patens, copyright Marco Schmidt.>


The Ambavioideae, despite not being very diverse, are widespread, with species found in the tropics of Africa, Asia and the Americas. Perhaps the best known ambavioid is the ylang-ylang tree Cananga odorata, native to south-east Asia, whose flowers are used as a source of perfume. Other south-east Asian ambavioids belong to the genera Cyathocalyx, Drepananthus and Mezzettia. The type genus, Ambavia, is native to Madagascar; other ambavioids in the genera Meiocarpidium, Cleistopholis and Lettowianthus are found in continental Africa. Finally, a single genus Tetrameranthus is found in South America. Most species of ambavioid are not systematically economically exploited but a number are locally used as sources of wood. The wood is light and not suitable for structural uses, but can be shaped and finished for utensils and other small items. The West African species Cleistopholis patens, whose Ghanaian name has been translated as 'salt and oil tree' (in reference to the taste of the bark when chewed), provides a fibrous bark that is readily stripped from the tree and is used for such purposes as matting and carrying straps (see here).

REFERENCES

Chatrou, L W., M. D. Pirie, R. H. J. Erkens, T. L. P. Couvreur, K. M. Neubig, J. R. Abbott, J. B. Mols, J. W. Maas, R. M. K. Saunders & M. W. Chase. 2012. A new subfamilial and tribal classification of the pantropical flowering plant family Annonaceae informed by molecular phylogenetics. Botanical Journal of the Linnean Society 169: 5–40.

Hydromantes: Salamanders in Different Places

There are times when biogeography is able to throw us some real puzzlers: organisms whose distribution seems to defy expectations. Among these mysteries, special mention must be made of the salamanders of the genus Hydromantes.

Gene's cave salamanders Hydromantes genei courting, copyright Salvatore Spano.


Hydromantes is a genus containing a dozen species from among the lungless salamanders of the family Plethodontidae. Plethodontids are the most diverse of the generally recognised families of salamanders, with over 450 known species found mostly in Central and South America. Hydromantes, however, is a geographically isolated genus in this family with its species found in two widely separated regions: California in western North America, and mainland Italy and Sardinia in Europe. Though some authors have advocated treating the species found on each continent as separate genera, both morphological and molecular studies have left little doubt that the group represents a discrete clade.

Distinctive features of Hydromantes compared to other plethodontids include feet with five, partially webbed toes and a weakly ossified, flattened skull (Wake 2013). Members of this genus capture prey with a projectile tongue which is the most extensive of any amphibian, extending up to 80% of the animal's total body length (Deban & Dicke 2004). There are some differences between North American and European species notable enough for the recognition of separate subgenera (there is something of a gigantic clusterfuck surrounding the names of said subgenera but the details are far too tedious to relate here). The three North American species of the subgenus Hydromantes have bluntly tipped tails that they use as a 'fifth leg' when navigating smooth and/or slippery surfaces, whereas the European species have unremarkable pointed tails. Historically, the North American Hydromantes species have been poorly known, being isolated to restricted ranges. Hydromantes shastae is found in limestone around Lake Shasta whereas H. brunus is found in a small area of mossy talus habitat along the Merced River in the foothills of the Sierra Nevada (Rovito 2010). The third species, H. platycephalus, is found at higher altitudes in the Sierra Nevada, well over 1000 m above sea level. Individuals found living on steep slopes are known to escape predators by tightly coiling their bodies and simply rolling down the slope (García-París & Deban 1995). A molecular analysis of H. platycephalus and H. brunus by Rovito (2010) identified the former species as derived from within the latter, and Rovito suggested that H. brunus may have originated in a remnant population from when H. platycephalus moved into lower altitudes during the Ice Age.

Mt Lyell salamander Hydromantes platycephalus, copyright Gary Nafis.


The seven or eight European species are mostly placed in the subgenus Speleomantes; a single species, Hydromantes genei, is divergent enough to be placed in its own subgenus Atylodes (though most recent studies have indicated that the European Hydromantes overall form a discrete clade). Hydromantes genei and three species of Speleomantes are found in caves on the island of Sardinia; the remaining Speleomantes species on mountains of mainland Italy. Molecular analysis suggests that H. genei became isolated on Sardinia about nine million years ago, with the ancestors of the Sardinian Speleomantes arriving later about 5.6 million years ago when the Mediterranean dried out during what is known as the Messinian Salinity Crisis (Carranza et al. 2008). The absence of any Hydromantes on neighbouring Corsica is something of a mystery, and it has been suggested that they may have been present there in the past before going extinct.

Extinction also seems the most likely explanation for Hydromantes' unusual distribution. The fossil record for the genus is minimal, and provides little information not already available from living species, but molecular dating attempts agree that the division between European and North American Hydromantes happened too recently to be related to the tectonic separation of the two continents. Such a scenario would also leave open the Hydromantes' absence in eastern North America. The description in 2005 of the Korean lungless salamander Karsenia koreana demonstrated the presence of plethodontids in eastern as well as far western Eurasia, and it seems possible that Hydromantes dispersed into Eurasia via the Bering Strait landbridge, becoming widespread across the continent before extinction reduced it to the isolated relicts it is today.

REFERENCES

Carranza, S., A. Romano, E. N. Arnold & G. Sotgiu. 2008. Biogeography and evolution of European cave salamanders, Hydromantes (Urodela: Plethodontidae), inferred from mtDNA sequences. Journal of Biogeography 35: 724–738.

Deban, S. M., & U. Dicke. 2004. Activation patterns of the tongue-projector muscle during feeding in the imperial cave salamander Hydromantes imperialis. Journal of Experimental Biology 207: 2071–2081.

García-París, M., & S. M. Deban. 1995. A novel antipredator mechanism in salamanders: rolling escape in Hydromantes platycephalus. Journal of Herpetology 29 (1): 149–151.

Rovito, S. M. 2010. Lineage divergence and speciation in the web-toed salamanders (Plethodontidae: Hydromantes) of the Sierra Nevada, California. Molecular Ecology 19: 4554–4571.

Wake, D. B. 2013. The enigmatic history of the European, Asian and American plethodontid salamanders. Amphibia-Reptilia 34: 323–336.

Leucicorus: FAKE EYES!

In an earlier post, I told you about the fishes known as brotulas. These are one of the most prominent groups of fish in the deep sea. They tend not to be attractive fish: their lack of outstanding dorsal and tail fins makes them look like something between an eel and a cod, and like many deep-sea fishes they look somewhat flabby and lumpish. There are numerous genera of brotulas out there; the individual in the photo below represents the genus Leucicorus.

Leucicorus atlanticus, from Okeanos Explorer.


Leucicorus belongs to the brotula family Ophidiidae, commonly known as the egg-laying brotulas though Leucicorus' own reproduction has (so far as I have found) not been directly observed. The feature that most immediately sets Leucicorus apart from other brotulas is the eyes: Leucicorus species have very large eyes but the actual lenses are rudimentary or absent (Cohen & Nielsen 1978). It almost looks like they grew bigger and bigger to cope with the low light of the deep sea before they just kind of gave up at some point.

Two species of Leucicorus are currently recognised, each known from separate parts of the world. Leucicorus lusciosus is found in the eastern Pacific, whereas L. atlanticus is known from around the Caribbean. The two species differ in meristic characters and proportions: for instance, L. lusciosus has more dorsal and anal fin rays, but fewer vertebrae and gill rakers, and has a deeper body (Nielsen & Møller 2007). Leucicorus has also been found in the vicinity of the Solomon Islands, but interestingly enough Nielsen & Møller (2007) identified the specimen found as L. atlanticus rather than L. lusciosus, despite the latter species' more proximate distribution. One wonders if perhaps a third species is involved, yet to be recognised.

REFERENCES

Cohen, D. M., & J. G. Nielsen. 1978. Guide to identification of genera of the fish order Ophidiiformes with a tentative classification of the order. NOAA Technical Report NMFS Circular 417.

Nielsen, J. G., & P. R. Møller. 2007. New and rare deep-sea ophidiiform fishes from the Solomon Sea caught by the Danish Galathea 3 Expedition. Steenstrupia 30 (1): 21–46.

Pontodrilus: Earthworms by Sea

Earthworms are primarily a terrestrial and freshwater group, sensitive to changes in the quality of their habitat. But there are some earthworm species that are tolerant of more saline environments. One such species is Pontodrilus litoralis, a widespread earthworm found in warm coastal habitats around the world, being recorded from such far-flung places as the Caribbean, the Mediterranean, Australia and Japan. The species is found in sandy or muddy soils in coastal habitats, including beaches, estuaries and around the roots of mangroves, and is able to tolerate salinities from 5 to 25 parts per thousand—that is, from fresh water to close to the standard salinity of sea water (Blakemore 2007).

Pontodrilus litoralis in its natural habitat, from here.


Pontodrilus litoralis is one of five species currently recognised in the genus Pontodrilus, though many more have been recognised in the past (Blakemore, 2007, listed eighteen species and subspecies now regarded as synonyms of P. litoralis). Characteristic features of the genus include an absence of nephridia in the anterior segments, and tubular prostrate organs opening to male pores on the eighteenth segment. The other Pontodrilus species have more restricted, non-coastal ranges; one, P. lacustris, is found free-swimming in Lake Wakatipu in New Zealand, whereas the other three are found in terrestrial habitats in Sri Lanka, China and Tasmania.

How P. litoralis achieved its wide distribution is currently unknown. If it arose prior to the separation of the land-masses on which it is now found then it would have had to have survived almost unchanged for hundreds of millions of years, which seems on the face of it unlikely. It seems more credible that it has dispersed more recently from its original point of origin, but while its green, spindle-shaped cocoons are often found attached to floating vegetation we do not know how long they can stand immersion in full-strength salt water. Nor do we know just where P. litoralis originated. It was first described in 1855 from the French Riviera so many authors have assumed the species is Mediterranean in origin. However, the distribution of related species seems to make an Indo-Pacific origin more likely. It may well be that P. litoralis was spread from its original home by humans, carried with rocks and sand used for ballast.

REFERENCE

Blakemore, R. J. 2007. Origin and means of dispersal of cosmopolitans Pontodrilus litoralis (Oligochaeta: Megascolecidae). European Journal of Soil Biology 43: S3—S8.

The Asteiids: Overlooked Flies

Flies are incredibly diverse, but they may be one of the least appreciated of the major insect groups. There are many significant fly lineages whose presence goes all but unnoticed by a small number of afficionados.

Asteia amoena, copyright Mick E. Talbot.


One of the largest clades of flies is the Schizophora, including many such familiar animals as house flies, blowflies, and fruit flies (of both varieties). The most distinctive feature marking this lineage is the ptilinal fold, a groove that runs around the face of the flies along the inner margin of the eyes and across above the antennal insertions. This groove marks the position of a large fold of soft cuticle, the ptilinum, that is used by the fly when it emerges from the hardened case, the puparium, in which it metamorphoses from a larva. The ptilinum expands like a bellows as the fly pumps its head full of liquid until the pressure causes the cap of the puparium to pop open. After this, the excess cuticle is folded away inside the head, never to emerge again, but the mark of its presence remains.

House fly Musca domestica emerging from its puparium, showing the inflated ptilinum. Copyright Alex Wild.


Schizophorans have commonly been divided between two main groups, referred to as the calyptrates and acalyptrates. The basis of this division is the presence (calyptrates) or absence (acalyptrates) of the calypters, lobes at the base of the wings that help in controlling flight. This is not an entirely phylogenetic system: the calyptrates are a single clade but the acalyptrates are not. The most familiar flies belong to the calyptrates (which include house flies and blowflies) despite the fact that acalyptrate flies are considerably more diverse. This is in part because many acalyptrates are very small flies, easily overlooked by the casual observer.

The Asteiidae are one such group of overlooked flies. They are found pretty much world-wide and can be very abundant in some habitats. Nevertheless, they are apparently not common in collections: their soft-bodiedness makes them tricky to preserve, and Grimaldi (2009) noted that tropical species living on rolled leaves of herbs such as bananas and gingers were reluctant fliers and so unlikely to be collected by passive intercept traps. Noteworthy features of asteiids compared to similar flies include a reduced wing venation, and an antennal arista bearing alternating rays (Friedberg 2009). In two genera, Polyarista and Anarista, the arista is reduced or lacking, replaced by a collection of long setae arising from the first flagellomere (Papp 2013).

Diagnostic features of Asteia amoena, from Walker's Insecta Britannica Diptera.


Because of their low collection rates, the natural history of asteiids is poorly known. As already noted, a number of species are found in association with vegetation; others have been raised from fungi. Grimaldi (2009) described Asteia species running "over the surface of a leaf in all directions with uniform effort, including backwards and sideways, which gives them an appearance of floating over the surface". Some species have mating rituals involving trophallaxis, in which a male attempts to entice a female by offering her a regurgitated droplet. If his offering meets her standards, they will collaborate to produce a new generation that will carry on in the same obscurity as the last.

REFERENCES

Freidberg, A. 2009. Asteiidae (asteiid flies). In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado. Manual of Central American Diptera pp. 1093–1096. NRC Research Press: Ottawa.

Grimaldi, D. A. 2009. The Asteioinea of Fiji (Insecta: Diptera: Periscelididae, Asteiidae, Xenasteiidae). American Museum Novitates 3671: 59 pp.

Papp, L. 2013. A new genus of Asteiidae with a key to the Old World genera (Diptera). Annales Historico-Naturales Musei Nationalis Hungarici 105: 199–205.

Scheloribates

Over the years, I've put up several posts about the diversity of oribatid mites. It's time for another one.

Scheloribates laevigatus, copyright R. Penttinen.


One of the largest genera of oribatids out there is the genus Scheloribates, for which well over 200 species have been described. Their distribution is pretty much worldwide; they are found in a range of microhabitats, such as in leaf litter, in pastures or marshes, or among rocks. Distinguishing features of the genus from other oribatids include well-developed, immobile pteromorphs, tridactylous (three-clawed) legs, and a notogaster with ten pairs of setae and three pairs of sacculi (little sac-shaped glandular openings) (Ermilov & Anichkin 2014).

Considering their abundance in soil habitats, Scheloribates probably have a significant role to play in decomposition and nutrient cycling. Studies on the diet of one of the better-known species, S. laevigatus, have found that it will eat almost any type of vegetable or fungal matter, though its preferred diet is microscopic algae (Hubert et al. 1999). Indeed, they are most abundant in damper habitats that would provide good conditions for the growth of such algae.

Scheloribates species may impact on human lives in other ways too. They are an intermediate host for the larvae of anoplocephalid tapeworms that infect livestock when the mites are accidentally ingested during grazing. S. laevigatus is a known host for at least eight tapeworm species in North America. Rates of tapeworm infestation in Scheloribates can be quite high; over 60% of the individuals of one species at a particular locality in Australia were infected (Lee & Pajak 1990). Scheloribates species are also noteworthy as a likely source of the toxic alkaloids found in the skin of arrow-poison frogs. The alkaloids are likely to be synthesised by the mites (as suggested by their presence in adults but not in juveniles, despite no known difference in diet between the two life stages) and then sequestered by the frogs after they eat the mites (Saporito et al. 2011). And if they eat enough mites, they end up becoming dangerous even to something the size of a human.

REFERENCES

Ermilov, S. G., & A. E. Anichkin. 2014. A new species of Scheloribates (Scheloribates) from Vietnam, with notes on taxonomic status of some taxa in Scheloribatidae (Acari, Oribatida). International Journal of Acarology 40 (1): 109–116.

Robert, J., V. Šostr & J. Smrž. 1999. Feeding of the oribatid mite Scheloribates laevigatus (Acari: Oribatida) in laboratory experiments. Pedobiologia 43: 328–339.

Lee, D. C., & G. A. Pajak. 1990. Scheloribates Berlese and Megascheloribates gen. nov. from southeastern Australia, with comments on Scheloribatidae (Acarida: Cryptostigmata: Oriopodoidea). Invertebrate Taxonomy 4: 205–246.

Saporito, R. A., R. A. Norton, N. R. Andriamaharavo, H. M. Garraffo & T. F. Spande. 2011. Alkaloids in the mite Scheloribates laevigatus: further alkaloids common to oribatid mites and poison frogs. Journal of Chemical Ecology 37: 213–218.

A Parasitic Eel?

The following post was inspired by an e-mail that I was sent recently by Sebastian Marquez. He told me about a friend of his catching a trevally when fishing, then cutting it open to find a snake eel inside the body cavity (but outside the stomach), wrapped around the trevally's internal organs. According to Sebastian, the lead suspicion for what had happened was that the eel had somehow burst out of the trevally's stomach before it was caught, and he wanted to know if I'd ever heard of anything similar. I didn't have an explanation for him, but his story did get me thinking about the snub-nosed eel.

Snub-nosed eel Simenchelys parasitica, from Jordan (1907).


The snub-nose eel Simenchelys parasitica is a small deep-sea eel, about 20 to 35 centimetres long. It has attracted note by being found a number of times burrowed into the body cavity of larger fishes with perhaps the most renowned case being two juveniles that were found nested inside the heart of a mako shark. This lead to the description of S. parasitica as an endoparasite (hence the species name). However, acceptance of this tag has been far from universal. The snub-nosed eel has been caught free-living more regularly than it has been found in other fish and because of its deep-sea habitat it has never been observed in life. An alternative suggestion has been that Simenchelys is normally a scavenger; because many of its recorded 'hosts' have been collected through non-targeted methods such as trawls, it is not impossible that the snub-nosed eels may have burrowed into their body cavity after they were already deceased.

It was with this conundrum in mind that the cranial anatomy of the snub-nosed eel was described by Eagderi et al. (2016). The jaws of Simenchelys are relatively short and muscular (hence its 'snub nose'). It also has teeth arranged in such a way that they form an even cutting edge (in contrast to the more spaced and uneven teeth of other eels). Eadgeri et al. came to the conclusion that the snub-nosed eel probably feeds by biting out plugs of flesh, in a similar manner to a cookie-cutter shark. Simenchelys also resembles a cookie-cutter in having large, fleshy lips that are probably used to form a seal between jaws and food source. A large hyoid ('tongue') apparatus probably works to provide suction to maintain the seal. The snub-nosed eel may also rotate while biting, a behaviour known from both cookie-cutters and other eels.

So is Simenchelys a parasite? It is probably not a habitual endoparasite, lacking as it does any clear adaptations to the endoparasitic lifestyle. There are fish that could be described as ectoparasites, in that they habitually feed on live animals larger than themselves in a manner that does not normally lead to the host's death. The cookie-cutter is one such fish; another is the candiru Vandellia cirrhosa, a small freshwater catfish from the Amazon basin that feeds on blood from the gills of other fish. It is possible that the snub-nosed eel could have a similar lifestyle to one of these. However, recorded evidence of its habits is even more consistent with scavengers such as hagfish and the candiru-açu Cetopsis candiru (another South American catfish) that tear flesh from the submerged bodies of dead animals, and may often burrow their way into the corpse's body cavity as they do so.

Of course, the two modes of feeding are not mutually exclusive. The only difference between predator and parasite in this scenario is whether the attacked animal is alive or dead, and the thing about flesh-feeders is that they're not always picky. A habitual scavenger may easily choose the opportunity to take a nibble from a still-living host, especially is said host is in some way incapacited (as a result of being swept up by a trawl, for instance). The snub-nosed eel may not be a habitual parasite, but it may be an opportunistic one.

REFERENCE

Eagderi, S., J. Christiaens, M. Boone, P. Jacobs & D. Adriaens. 2016. Functional morphology of the feeding apparatus in Simenchelys parasitica (Simenchelyinae: Synaphobranchidae), an alleged parasitic eel. Copeia 104 (2): 421–439.

Of Shrimp Plants and Bear's Breeches

For today's semi-random post, I drew the plant subfamily Acanthoideae. As recognised by Scotland & Vollesen (2000), the Acanthoideae is the largest of the subfamilies of the Acanthaceae by a considerable margin, including about 95% of the family's 2500+ species. Though perhaps not hugely familiar to readers in more temperate climes, the Acanthoideae are one of the dominant groups of herbs and shrubs in tropical parts of the world.

Golden shrimp plant Pachystachys lutea, copyright Dryas.


The Acanthoideae have been recognised as a morphological group since the late 1800s and their integrity has been confirmed by more recent molecular studies. They are distinguished from related plants (within the Lamiales, the order that also includes such plants as the mints and snapdragons) by having capsular fruits that dehisce explosively when mature to scatter their seeds. The seeds are attached within the capsule by hook-shaped stalks called retinacula that presumably play a role in determining how the seeds are released. A classification of Acanthaceae published in 1965 by Bremekamp restricted the family to species with explosive fruits and retinacula, dividing them between two subfamilies, the Acanthoideae and Ruellioideae, based on the absence or presence, respectively, of cystoliths. These are outgrowths of the epidermal cell walls that are impregnated with calcium carbonate. They are visible in the stems and leaves, at least in dried specimens, as hard white streaks. As phylogenetic studies have supported division of Acanthoideae in the broad sense between a cystolith-possessing and a cystolith-lacking clade, the decision whether to recognise 'Ruellioideae' as a separate subfamily comes down to a ranking choice only. At lower levels, the classification of Acanthoideae is less straightforward. Over two hundred genera of Acanthoideae are recognised but just three of those—Justicia, Strobilanthes and Ruellia—account for about half the total number of species. Each of these mega-genera is morphologically diverse and likely to be para- or polyphyletic with regard to related taxa, raising the distinct likelihood of future revisions.

Spiny bear's breeches Acanthus spinosus, copyright Magnus Manske.

Economically, few of the Acanthoideae are of great significance except for a number of species being grown ornamentally. One such species is Acanthus mollis, which goes by the vernacular name of 'bear's breeches' (why, I have absolutely no idea). Acanthus was a popular decorative motif in classical Greece and forms the basis for the design of Corinthian columns. Its use as an ornamental has lead to it becoming regarded as an invasive weed in some regions, largely because this is one of those garden plants that Just Will Not Die, spreading easily from seeds and tubers. We've got some in a pot outside that is currently flourishing despite having been burnt down to a nub by the searing Perth summer sun, metaphorically shouting its defiance at an uncaring world.

REFERENCE

Scotland, R. W., & K. Vollesen. 2000. Classification of Acanthaceae. Kew Bulletin 55 (3): 513–589.

Magnificent Eurhins

Eurhinus festivus(?), copyright Andreas Kay.


Weevils are one of the most incredibly diverse of beetle groups, coming in an incredible array of shapes and structures, but they are not usually renowned for their bright colours. Nevertheless, in a group of this size, there is always scope for surprise: witness the image above. Eurhinus is a genus of absolutely stunning metallic-coloured weevils native to Central and South America; one species, E. magnificus, was first recorded in Florida in 2002 and has since become established there. The photo above was identified on Flickr as E. magnificus but looking over the descriptions in Casey (1922) I suspect it is more likely to be the closely related E. festivus. Eurhinus magnificus differs in having patches of red on the pronotum and elytral humeri (the 'shoulders'); see photos here, for instance.

Eurhinus species feed on vines of the Vitaceae, the grape family. Eggs are inserted into young stems where the larvae cause distinct galls as they develop. It does not look like they are known to cause significant damage to economically important species though studies on whether it can successfully attack grapes are inconclusive.

REFERENCE

Casey, T. L. 1922. Studies in the rhynchophorous subfamily Barinae of the Brazilian fauna. Memoirs on the Coleoptera 10: 1-520.

Finches in Drag

Green-headed tanager Tangara seledon, copyright Dario Sanches.


In many parts of tropical South America, it is common to see small flocks of brightly coloured small birds foraging among vegetation, plucking off berries or hunting for insects. In many cases, these flocks may contain individuals of multiple or even several species. These are the tanagers, one of the Neotropical region's most characteristic bird families.

Tanagers are members of the bird clade known as the nine-primaried songbirds (so-called because their wings have nine functional primary feathers rather than the ten of other songbirds) that also includes the finches, buntings and cardinals. The largest genus of tanagers, and indeed one of the larger genera of birds in general, is Tangara. This genus includes about fifty species found in various parts of the neotropics. In their overall structure, they are fairly uniform: small, sturdy birds with a stout, moderate-length bill and an average-length tail (Hilty 2011). In other words, they have a fairly unremarkable, finchy-type appearance. In colour and patterning, however, they are considerably more varied, to the extent that I am at a loss to know where to begin. There are species of a rich, deep blue and of a bright, emerald green. There are species with bold, contrasting patterns of blues, blacks, greens or golds; there are species of a solid, uniform brilliance. There are species with caps or chests of orange or black. There are even a few, such as the plain-coloured tanager Tangara inornata, that eschew the gaudy pigments of their congeners entirely in favour of more restrained patterns of greys and beiges. In many species, males and females show little or no difference in appearance; however, in the black-capped group (including species such as the black-capped tanager T. heinei), the males have contrasting patterns of black and blue or yellow whereas the females are largely green and grey.

Golden tanager Tangara arthus, copyright Alejandro Bayer Tamayo.


As noted above, tanagers feed on a mixed diet of fruit and insects. The fruit part is dominated by small berries that they can either swallow whole or mash with their bills before swallowing them piecemeal. Studies on the mixed-species flocks formed by Tangara species have found that while different species show very little variation in how they obtain the fruit component of their diet, they usually show very distinct specialisations in how they forage for insects. Some hunt for insects along branches, others prefer to look on leaves. Branch-hunting species may differ in the thickness and density of branches preferred, or in the mode of searching employed. For instance, the golden tanager T. arthus and flame-faced tanager T. parzudakii can both be found foraging on moss-covered branches, but the flame-faced tanager usually catches insects by probing directly into the moss whereas the golden tanager usually either focuses on the moss-free sections or catches insects sitting on the moss surface without probing. A few species catch insects aerially, making short sallies from a perch.

Blue-grey tanager Thraupis episcopus, indicated by phylogenetic analysis as a species of Tangara, copyright Mdf.


Somewhat unexpectedly for a genus of this size and diversity in a group as taxonomically challenging as the tanagers, molecular phylogenetic studies have largely corroborated Tangara's monophyly. They have also supported the monophyly of most of the species groups recognised within the genus of the basis of similarities in plumage patterns (Sedano & Burns 2010). The only exception has been the discovery that many of the species previously included in the genus Thraupis form a clade nested within Tangara, leading to the suggestion that these two genera should be synonymised (apart from in informal discussions online, I'm not aware of anyone suggesting the alternative that Tangara be split). The 'Thraupis' species are larger and plainer in coloration than most other Tangara species. A few taxonomists have also suggested that the colourful green tanagers of the genus Chlorochrysa should be included in Tangara, but this relationship has not been supported by molecular data. Chlorochrysa species are glossier than the often more matt-coloured Tangara, and they have an acrobatic mode of foraging involving postures such as regularly hanging upside-down that differ from any Tangara species.

REFERENCES

Hilty, S. L. 2011. Family Thraupidae (tanagers). In: del Hoyo, J., A. Elliott & D. Christie. Handbook of the Birds of the World vol. 16. Tanagers to New World Blackbirds pp. 46–329. Lynx Edicions: Barcelona.

Sedano, R. E., & K. J. Burns. 2010. Are the northern Andes a species pump for Neotropical birds? Phylogenetics and biogeography of a clade of Neotropical tanagers (Aves: Thraupini). Journal of Biogeography 37: 325–343.

The Wingless Penguin

A couple of weeks ago, I put up a page on the 'terrestrial penguin' Cladornis pachypus, described from the Oligocene of Patagonia by the Argentine palaeontologist Florentino Ameghino. As it happens, Cladornis wasn't the only unusual penguin recognised from the Patagonian fossil record by Ameghino nor was it even necessarily the most unusual. That title should probably go to another species, the wingless Palaeoapterodytes ictus.

Anterior (left) and posterior view of humerus of Palaeoapterodytes ictus, from Acosta Hospitaleche (2010). Scale bar = 10 mm.


Like Cladornis, Palaeoapterodytes was based on only a single bone, in this case a humerus (upper wing bone) from the Early Miocene. And also like Cladornis, Ameghino's description of this bone indicated a truly remarkable bird. The distal part of the humerus lacked any sign of the facets that would normally articulate with the succeeding wing bones and, as a result, Ameghino concluded that the wing skeleton had been reduced to the humerus only. The crest and pits on the humerus marking the attachment of the wing muscles were also reduced. Ameghino's Palaeoapterodytes presumably had wings reduced to the merest nubs, effectively functionless and probably of little mobility. Nevertheless, the humerus of Palaeoapterodytes remained relatively robust, its breadth little less than that of other penguins.

I am not aware of any other bird with a wing structure anything like this. In other birds without functional wings, the entire wing skeleton becomes reduced, not simply truncated. Perhaps the closest approximation I have found is the wing of Hesperornis, which also lacks known wing bones beyond the humerus. However, the Hesperornis humerus is slender and gracile, and even without direct indication of the presence of more distal bones, it still looks to retain some remnant of the ancestral articulation. Also, the whole concept of a wingless penguin is decidedly problematic. Hesperornis derived its main propulsion in swimming from its feet and so its wings became reduced because they served little function. Penguins, on the other hand, get most of their propulsion from their wings, swimming in a manner that has been compared to flying underwater. Despite being flightless, penguins retain a wing skeleton that is, if anything, even more well developed than that of their flying relatives. For Palaeoapterodytes to have lost functional wings, it would have somehow had to change its mode of propulsion.

Reconstruction of the Palaeoapterodytes humerus with missing sections restored, from Acosta Hospitaleche (2010).


As a result, even while authors were cautiously considering Ameghino's interpretation of Cladornis, they treated Palaeoapterodytes with more scepticism. This scepticism was eventually concerned when the humerus was re-examined by Acosta Hospitaleche (2010). The reason for the lack of structure at its distal end was very simple: the original distal end had been broken off. The apparent lack of development of the muscle attachment structures was the result of erosion, not any indication of the bone's original appearance. When alive, Palaeoapterodytes had probably been very similar to, if not identical with, one of the several other penguin species known from around the same time and place. Unfortunately, the state of preservation of the type humerus is so poor that its exact identity cannot be determined, and Palaeoapterodytes ictus has been cast into the taxonomic limbo of nomen dubium. Ameghino's Cladornis may remain an intriguing mystery, but his Palaeoapterodytes is just a red herring.

REFERENCES

Acosta Hospitaleche, C. 2010. Taxonomic status of Apterodytes ictus Ameghino, 1901 (Aves; Sphenisciformes) from the Early Miocene of Patagonia, Argentina. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 255 (3): 371–375.

Brittle Stars, Brittle Taxa

Amphiura arcystata brittle stars extending their arms above the sediment, copyright James Watanabe.


The brittle stars are something of the poor cousin among echinoderm classes. Their tendency to relatively small size and cryptic habitats means that they do not attract the level of attention given to starfish, sea urchins or sea cucumbers. Despite this, they are perhaps the most diverse of the living echinoderm classes, with more recognised species around today than any other.

It should therefore come as no surprise that the internal classification of brittle stars remains decidedly up in the air. The basic framework of the surrent system was established over a hundred years ago by Matsumoto (1915) and changes to this arrangement since have been fairly cosmetic. However, a significant challenge to Matsumoto's system has been arisen following the input of molecular data to the mix: many of Matsumoto's higher groupings have not been supported by moleculat analyses. Perhaps the nail in the Matsumoto system's coffin has come from a recent publication by Thuy & Stöhr (2016) who found that a formal analysis of morphological data also failed to support the pre-existing classification. At this point in time, we know that a new classification of brittle stars is needed but we don't yet know what form it will take.

Excavated specimen of Amphiuridae, copyright Arthur Anker. The radial plates are visible as a pair of bars alongside the base of each arm; I don't think that the genital plates are visible externally.


Perhaps one of Matsumoto's groupings that will survive the transition is the Gnathophiurina. Notable features of this group include a ball-and-socket articulation between the radial shields (large plates that sit on the aboral side of the central body on either side of the insertion of each arm) and the genital plates (sitting below and alongside the radial shields), with the socket in the radial shield and the ball on the genital plate. The genital plates are also firmly fixed to the basal vertebra of each arm. I haven't been able to find what the functional significance of this arrangement is, such as whether it renders the body more flexible that in other groups where the radial-genital plate articulation is more fixed. At least one of the families of Gnathophiurina, the Amphiuridae, includes species that commonly live in burrows with the tips of their arms extended into the water column, using their tube feet to capture food particles (Stöhr et al. 2012). In contrast, some Ophiotrichidae are epizoic, living entwined around black corals and the like. The Gnathophiurina as a whole seem to be most diverse in relatively shallow waters.

Matsumoto's (1915) original concept of the Gnathophiurida included species that are now classified into four families, the Amphiuridae, Ophiotrichidae, Amphilepididae and Ophiactidae, and recent analyses have returned results not inconsistent with this association. In Thuy & Stöhr's (2016) morphological analysis, Gnathophiurina species all belong to, and make up the bulk of, their clade IIIc. In the molecular analysis presented by Hunter et al. (2016), the families belong to two separate clades but the branch separating them is very weakly supported. Further research is needed, of course, but it may turn out that Matsumoto was on to something when he focused on that ball-and-socket joint.

REFERENCES

Hunter, R. L., L. M. Brown, C. A. Hill, Z. A. Kroeger & S. E. Rose. 2016. Additional insights into phylogenetic relationships of the Class Ophiuroidea (Echinodermata) from rRNA gene sequences. Journal of Zoological Systematics and Evolutionary Research 54 (4): 269–275.

Matsumoto, H. 1915. A new classification of the Ophiuroidea: with descriptions of new genera and species. Proceedings of the Academy of Natural Sciences of Philadelphia 67 (1): 43–92.

Stöhr, S. T. D. O'Hara & B. Thuy. 2012. Global diversity of brittle stars (Echinodermata: Ophiuroidea). PLoS One 7 (3): e31940.

Thuy, B., & S. Stöhr. 2016. A new morphological phylogeny of the Ophiuroidea (Echinodermata) accords with molecular evidence and renders microfossils accessible for cladistics. PLoS One 11 (5): e0156140.

Public Service Announcement: Page priority is Not A Thing


I'll admit it, the rules governing taxonomy and nomenclature can seem horribly complicated when you don't spend a lot of time dealing with them directly. This isn't because taxonomy itself is inherently complicated: in fact, the underlying principles are really quite simple. The primary rationale behind each of the various codes of nomenclature can be distilled down to two points: (a) each single taxon should have a single name that differs from that of any other taxon, and (b) if more than two possible names can be assigned to a single taxon then the name given to that taxon first should be the one used (this latter point is called the principle of priority). Where things get complicated is that taxonomy is a process run by and for human investigators. And if there's one thing that can be said about all human endeavours, from science to politics to the selection of sports teams, it's that any application of simple principles is going to run afoul of complex practicalities. So questions arise that any code of nomenclature has to deal with: is it always ideal to simply use the oldest name? How do we determine which name is 'oldest', and what do we do if it's not clear? Each of the codes has developed its own methods of dealing with these questions and others, but it is not uncommon for these methods to be overlooked or misunderstood, sometimes even by people who might be expected to know better. One particularly pernicious misunderstanding that I've often come across (and which I was reminded of recently by one paper in particular that will go unnamed) is 'page priority'.

As mentioned above, it is not uncommon for two or more names to turn out to be synonymous without one particular name being obviously 'older'. Perhaps the papers naming each species were published at the same time, or they were named within a single paper. In these situations, many authors will invoke the principle of page priority in determining which name should be used: the name which appeared in an earlier place in the publication (say, on p. 23 rather than p. 25) should be the one used. The problem is that, in the case of the International Code of Zoological Nomenclature at least, no such principle is mandated (I'm not so familiar with the other codes, but I don't think they have page priority either). Instead, the code resolves indeterminate priority through the principle of the 'first reviser'. In the code's own words:
24.2.1. When the precedence between names or nomenclatural acts cannot be objectively determined, the precedence is fixed by the action of the first author citing in a published work those names or acts and selecting from them; this author is termed the "First Reviser".

In other words, the question of which name takes priority is determined by the choice of the first person who treats them as synonyms. Any subsequent authors are required to abide by the decision made by the first reviser. There is no restriction placed on how the first reviser should make their decision; if they want to follow page priority, they're perfectly free to do so. The problem comes when a first reviser doesn't follow page priority, only to have later authors claim they made the "wrong" decision. Maybe the name that appeared on a later page in the original publication was better described, or had been more commonly referred to by later authors. Whatever the situation, the decision of the first reviser is final. No correspondence shall be entered into.

"Page priority" is a bit of a case of what's been called a hypercorrection, when someone 'corrects' something that was already right. Someone who's familiar with a principle (in this case the principle of priority) but doesn't fully understand the reasons for the principle may try to apply it more widely than they should. So, for instance, someone who knows the plural of 'hippopotamus' is 'hippopotami' may assume that the plural of 'octopus' is 'octopi'. Hypercorrections persist because, on a superficial level, they 'make sense'. Sadly, being sensible is no barrier to being wrong.

Interestingly enough, there was a brief time in zoological nomenclature when page priority was a mandated rule (Dubois 2010). Between 1948 and 1953, a page priority clause was inserted into the Règles Internationales de la Nomenclature Zoologique, the earlier code of zoological nomenclature that was used before 1961. In 1953, this clause was suppressed and invalidated, and the first reviser principle now applies almost universally. Anyone who argues that a taxonomic decision violates 'page priority' can be safely ignored.

REFERENCES

Dubois, A. 2010. Retroactive changes should be introduced in the Code only with great care: problems related to the spellings of nomina. Zootaxa 2426: 1–42.

Parastenocaris

Parastenocaris brevipes, copyright A. Hobaek.


It's time for another consideration of the overwhelming diversity of stygofaunal copepods. Parastenocaris is a genus of copepods found on almost all the landmasses of the world except, presumably, Antarctica (New Zealand also stands out as an intriguing void in the genus' distribution). The majority of species in this genus are insterstitial, mostly found in soils saturated with fresh water; a small number of species are found in brackish habitats such as estuaries. A few species have also been found above ground, particularly in the tropics (Galasi & Laurentiis 2004). The type species of the genus, P. brevipes, has been found in sphagnum bogs (Karanovic 2005).

As commonly recognised, Parastenocaris is a pretty huge genus, with well over 200 species having been assigned to it over the years. However, the genus has been poorly defined and many authors have questioned its integrity. Galasi & Laurentiis (2004) suggested that Parastenocaris should be restricted to those species most closely related to the type species, P. brevipes. Such a group would still be pretty cosmopolitan; indeed, P. brevipes itself has a Holarctic distribution and is known from both Europe and North America (this stands in pretty stark contrast to the super-short ranges of some stygofaunal copepods). Distinctive features of this restricted P. brevipes group include a characteristic endopodal complex on leg 4 of the male, with the endopod hyaline and with one or two large claws. In contrast, the leg IV endopod in females is long and distally serrate.

Parastenocaris lacustris, from here


Members of the Parastenocaris brevipes groups are found closer to the soil surface than many other members of their family (Karanovic 2005). They are also relatively large, reaching the absolutely monstrous size (I'm sure) of half a millimetre or more. Karanovic (2005) suggested that this larger size could reflect the larger size of the sand grains they live among closer to the surface, or it could simply reflect their access to more reliable food sources that are available to their more deeply buried relatives.

REFERENCES

Galasi, D. M. P., & P. de Laurentiis. 2004. Towards a revision of the genus Parastenocaris Kessler, 1913: establishment of Simplicaris gen. nov. from groundwaters in central Italy and review of the P. brevipes-group (Copepoda, Harpacticoida, Parastenocarididae). Zoological Journal of the Linnean Society 140: 417–436.

Karanovic, T. 2005. Two new subterranean Parastenocarididae (Crustacea, Copepoda, Harpacticoida) from Western Australia. Records of the Western Australian Museum 22: 353–374.

The Patagonian Land Penguin


Take a good look at the figure above, which comes from Mayr (2009). It shows the fossilised tarsometatarsus (the fused long bone of the foot) of a bird from the late Oligocene of Patagonia. This may be one of the single most mysterious specimens in the fossil record. It represents all we know to date of Cladornis pachypus, described by Argentinean palaeontologist Florentino Ameghino in 1895. The appearance of the bone, being very broad and flat relative to its length, is quite bizarre and does not much resemble the tarsometatarsus of any other known bird.

The first thing that should be pointed out is that, whatever it was, Cladornis was a large bird. The specimen is not completely preserved (part of the proximal end of the bone has been lost) but its overall shape suggests that its original length was probably not too much longer than what we have. As such, the tarsometatarsus was probably comparable in length to that of a large pelican. However, it was much wider relative to length than that of a pelican, suggesting the possibility of a more robust bird. The shape of the bone's end indicates that the toes would have been widely spaced, and it may have even approached a zygodactyl arrangement (with two toes pointed rearwards and two forwards, like a modern parrot*) (Mayr 2009).

*When explaining this to my partner, I suggested that he imagine a parrot the size of a pelican. He shuddered and declared that he would rather not.

When Ameghino (1895) first described Cladornis, he interpreted it as an aquatic bird and suggested a relationship to the penguins, albeit in an extinct family Cladornidae (later authors would correct this to Cladornithidae). Later, noticing that it was preserved in association with terrestrial mammals, he declared that it was not marine and was possibly even terrestrial (he also included another species from the same formation, Cruschedula revola, in the Cladornithidae; this species is based on part of a scapula and there is no telling if it was related to Cladornis or not). He still maintained its relationship to the penguins (Ameghino 1906). Ameghino had a bit of a thing for trying to find the origins of all major modern vertebrate groups in his native South America (one of his other works was a book arguing for an Argentinean origin of humans) and it is possible that this was in play here. Nevertheless, the idea of a 'Patagonian land penguin' held sway until Simpson's (1946) review of the fossil penguins, in which he declared that Cladornis was "so very unlike any other penguin, recent or fossil, that I can only consider its reference to that group as erroneous".

This left Cladornis' taxonomic position completely up in the air (the question of whether Cladornis itself could get up in the air is, of course, currently completely unswerable). Wetmore (1951) included Cladornis in the Pelecaniformes, because...reasons. The closest he gave to an explanation was, "The only suggestion that has come to me is that possibly they may belong in the order Pelecaniformes, in which I have placed the family tentatively in the suborder Odontopteryges, where it is located with two others of almost equally uncertain status. This allocation is wholly tentative and is no indication of belief in close relationship in the three diverse groups there assembled". He would later move Cladornis into its own suborder, Cladornithes, and no close relationship to the 'Odontopteryges' (now the Pelagornithidae) has been suggested since. Our current understanding of bird phylogeny finds Wetmore's remaining 'Pelecaniformes' to correspond to three or four independent clades (the Pelecanidae, Suliformes, Phaethontidae and probably Pelagornithidae) so his assignment of Cladornis to this group becomes almost completely uninformative.

Which is pretty much where we're forced to leave things. Mayr (2009) included Cladornis in his chapter on 'land birds', with other taxa discussed in this chapter belonging to the clade Telluraves. However, this was motivated more by a lack of any idea what to do with it otherwise than anything else (it is possible that Cladornis' sub-zygodactyly played a role, but not all zygodactylous birds belong to the Telluraves). I did notice a similarity in proportions between the Cladornis tarsometatarsus and the corresponding bone in the large phorusrhacid Brontornis, making me wonder if anyone had ever compared the two, but this may well be only superficial. Most recent authors have assumed that the Cladornis tarsometatarsus is simply too weird, too unique, for any resolution of its affinities to be reached without first finding more complete remains of the animal.

REFERENCES

Ameghino, F. 1895. Sur les oiseaux fossiles de Patagonie et la aune mammalogique des couches a Pyrotherium. Boletín del Instituto Geográfico Argentino 15 (11–12): 501–602.

Ameghino, F. 1906. Enumeración de los Impennes fósiles de Patagonia y de la Isla Seymour. Anales del Museo Nacional de Buenos Aires, serie 3, 6: 97–167.

Mayr, G. 2009. Paleogene Fossil Birds. Springer.

Simpson, G. G. 1946. Fossil penguins. Bulletin of the American Museum of Natural History 87 (1): 1–99.

Wetmore, A. 1951. A revised classification for the birds of the world. Smithsonian Miscellaneous Collections 117 (4): 1–22.

Camponotus: A Sugary High

I think I may have said before that Australia is the land of ants. When travelling in Australia's arid regions (i.e. most of the continent), ants are often the most visible animals about. Perhaps the most visible of all Australia's ants are the meat ants (Iridomyrmex), but not too far behind them are the sugar ants of the genus Camponotus.

Workers and emerging queens of banded sugar ants Camponotus consobrinus around the nest opening, copyright Steve Shattuck.


Camponotus is a genus of the ant subfamily Formicinae found pretty much everywhere around the world that ants are to be found. It is massively diverse: well over 1000 species have been assigned to this genus over the years, with probably more to be described. They are correspondingly diverse in habits and appearance. Some are among the giants of the ant world, others are much smaller. Some form massive colonies that are difficult to miss and forage during the day, others are more retiring and emerge only at night. Some construct their nests in holes under the grounds, others hollow out wood or use the holes left by other wood-boring insects. Most (but not all) Camponotus species exhibit some form of worker polymorphism: rather than having just a single worker caste, a colony will often include large major workers and much smaller minor workers, with the two forms superficially looking quite different. Sometimes the distinction between majors and minors will be quite clear, other times there will also be workers of intermediate sizes. In some Australian species, known as honeypot ants, there are specialised workers called 'repletes' who spend their lives hanging in one spot inside the nest, being fed by the other active workers until their gasters swell into engorged round balls. These repletes serve the colony as a living larder, able to regurgitate their stored excess of food when needed by their nestmates. Despite all this diversity, most Camponotus species are readily recognisable as Camponotus: they usually lack spines on the mesosoma (the 'thorax'), the back end of which is narrow and often arched. This smoothness and slimness gives Camponotus a distinctive look that kind of puts me in mind of the ant version of a greyhound. The majority of Camponotus species also differ from other ants in lacking the metapleural gland, a gland producing an antibiotic chemical whose opening is usually visible near the rear of the mesosoma.

Camponotus aurocinctus, copyright Steve Shattuck.


Camponotus species have been referred to in Australia as 'sugar ants' in reference to their diet, which is commonly dominated by the sugary excretions of plant-sucking bugs that they attend. In other parts of the world, they have sometimes been referred to as 'carpenter ants' in reference to the wood-tunneling habits of their most notorious representatives. Bug-derived honeydew is high in sugar but low in other essential nutrients, so the ants also feed on things such as the scavenged bodies of the bugs themselves after death. They are also probably assisted in meeting their nutritive needs by Blochmannia, an endosymbiotic bacterium that infests specialised cells in the gut of Camponotus and closely related genera (Wernegreen et al. 2009). Genetic data from the endosymbiont indicates that it probably synthesises nutrients the ant does not otherwise ingest. It may also play some role in compensating for an absence of metapleural gland secretions. As well as the gut, Blochmannia infest the ovaries of reproductive females and are passed to the next generation via the developing oocytes. Phylogenetic analysis of Blochmannia indicates that it is closely related to other endosymbiotic bacteria found in mealybugs, and it is possible that the ancestors of Camponotus picked it up in the course of feeding on honeydew.

Honeypot ant Camponotus inflatus repletes hanging in the nest, copyright Mike Gillam.


The sheer size of Camponotus as a genus has been a challenge to understanding relationships within the genus. Over thirty subgenera have been proposed at one time or another, but many of these are poorly defined and many authors eschew using them in favour of informal species groups. It does not help matters that, since the early 20th century, most reviews of Camponotus have been conducted at a local rather than a global level. Those studies that have touched on Camponotus phylogeny in recent years suggest the need for a large-scale revision, with few of the subgenera supported as monophyletic.

REFERENCES

Wernegreen, J. J., S. N. Kauppinen, S. G. Brady & P. S. Ward. 2009. One nutritional symbiosis begat another: phylogenetic evidence that the ant tribe Camponotini acquired Blochmannia by tending sap-feeding insects. BMC Evolutionary Biology 9: 292. doi:10.1186/1471-2148-9-292.