The Violet Demoiselle

Meet the violet demoiselle Neopomacentrus violascens (shown above in a photo by J. E. Randall). This little fish (adults get up to about 7.5 cm in length) is found in tropical waters of the western Pacific, from Japan in the north, south and east to northern Australia and Vanuatu. They usually associate in large schools around inshore reefs, and can commonly be found hanging around outcropping structures over soft bottoms such as coral or rocky outcrops, or wharf pilings (Koh et al. 1997). Violet demoiselles feed on small plant or animal plankton, such as copepods or algae.

The genus this species belongs to, Neopomacentrus, is one of the more recently recognised genera of the damselfish family Pomacentridae. It is similar to two larger genera in the family, Abudefduf and Pomacentrus, but differs from the former in having the hind margin of the preopercle (the anterior one of the bones making up the operculum or gill cover) crenulate or serrate rather than smooth. Pomacentrus has a similar preopercle, but has the suborbital region at least partially naked whereas Neopomacentrus has that region entirely scaly. Neopomacentrus violascens has a distinctive colour pattern, which is mostly a purplish brown, with bright yellow on the caudal fin and the rear of the dorsal fin.

According to Fishbase, individuals of this species form pairs when mating, and the females lay eggs that sink to the bottom and stick to the substrate. The eggs are then guarded and aerated by the males. I have come across reference to this species having been bred in captivity though I get the impression that they are not one of the most commonly kept aquarium fish. This may be because they are somewhat dull in coloration compared to related species, and they are fairly retiring in character. A recent blog post at Zoo Volunteer noted that damselfish species are rarely bred commercially due to the difficulty of providing suitable conditions. Instead, the market for species of this family is usually supplied with wild-caught individuals, commonly collected through the use of cyanide to essentially suffocate the fish until they lose conciousness. Not particularly pleasant for the fish, and arguably not that pleasant for the aquarist either as fish obtained in this method tend to have a much reduced lifespan.

REFERENCES

Koh, J. R., J. G. Myoung & Y. U. Kim. 1997. Morphological study on the fishes of the family Pomacentridae. I. A taxonomical revision of the family Pomacentridae (Pisces; Perciformes) from Korea. Korean Journal of Systematic Zoology 13 (2): 173–192.

A Place for Worms

When we think of endangered species, we tend to focus on the charismatic vertebrates, such as pandas, parrots, tigers or turtles. But endangered species may come from all walks, crawls or wriggles of life. Have you ever considered, for instance, the plight of endangered earthworms?

An unidentified species of Glossodrilus, copyright Thibaud Decaens.

Glossodrilus is a genus of earthworms found in tropical and subtropical regions of Central and South America. They are mostly fairly small as earthworms go, averaging only a few centimetres long and one or two millimetres in diameter. The largest, G. oliveirai from Brazil's Roraima State and Guyana, is about 25 centimetres long; the smallest, G. tico from Roraima and Venezuela, is less than two centimetres in length. Most species lack pigmentation, meaning that they appear greyish from the colour of their gut contents. A single species, G. freitasi from Amapá State in Brazil, is a bright violet in colour. Other diagnostic features of the genus include: eight setae per segment, arranged in regular series; a pair of (or sometimes one) calciferous glands sitting above the oesophagus in segments XI to XII; two or three pairs of lateral hearts in segments VII to IX, and two pairs of intestinal hearts in X and XI; and a pair of testes in segment XI. Glossodrilus is distinguished from a closely related earthworm genus, Glossoscolex, by the absent of a pair of muscular copulatory chambers associated with the male ducts in the latter genus (Righi 1996).

Over sixty species have been assigned to Glossodrilus; as is usual with earthworms, they are mostly distinguished by internal characters such as features of the reproductive systems. They are most diverse in upland regions, with many species inhabiting high rain forest. A few species in the northernmost or southernmost parts of the genus' range inhabit secondary grasslands. Glossodrilus species are conspicuous by their absence in the Brazilian central plateau, and only infrequently present in lowland Amazonia (Righi 1996).

And this is where the question of conservation comes in. You see, the greater number of Glossodrilus species are known only from a very restricted area (Lavelle & Lapied 2003). Part of this may be an artefact of sampling: in more recent decades, our understanding of South American earthworm diversity has been heavily shaped by one researcher, Gilberto Righi of the Universidade de São Paulo (I referred to him briefly in an earlier post on Amazonian earthworms), and we know little of areas where Righi did not collect specimens himself or from where he did not receive specimens supplied by ecological surveys. Nevertheless, sampling has probably been extensive enough to expect that the low number of shared species between different regions will hold firm at the broad scale at least. Most Glossodrilus species (and other native South American earthworms) are dependent on old-growth habitats; as land is cleared for farming, forestry and the like, exotic and invasive earthworm species take over. It would be all to easily for the little Glossodrilus to find themselves homeless, and slip into extinction without any to mark their passing.

REFERENCES

Lavelle, P., & E. Lapied. 2003. Endangered earthworms of Amazonia: an homage to Gilberto Righi. Pedobiologia 47: 419–427.

Righi, G. 1996. Colombian earthworms. Studies on Tropical Andean Ecosystems 4: 485–607.

Large Yellow Underwings

Above is an example (copyright Richard) of the large yellow underwing Noctua pronuba, the most widespread species of its genus. Noctua pronuba is a relatively large moth, with a wingspan of up to 60 mm. The forewings are fairly dull and dark in colour, but the hindwings are a bright yellow-orange (hence the vernacular name) with a black border. It can usually be found out and about in mid summer to early autumn. Its larvae are one of the types of caterpillar known as 'cutworms', which live buried in the soil during the day and emerge at night to feed. They get their vernacular name because their soil-dwelling habits mean that they tend to feed on plants from the base, often toppling small plants and seedlings like a lumberjack taking down a tree. The larvae of the large yellow underwing are not overly discerning in their food preferences; though they most often feed on grasses, they will quite happily dine on other herbaceous flowering plants such as legumes.

Larva of Noctua pronuba, copyright Nigel Richards.

The large yellow underwing is native to a wide part of the Palaearctic region, i.e. Europe and northern Asia. In 1979, it was also found introudced to Nova Scotia in North America. Since then, it has spread rapidly and can now be found over much of temperate North America, reaching British Columbia in the west and Louisiana in the south (Copley & Cannings 2005). The large yellow underwing is a strong flier and is known to undertake significant migrations in its native range. Females may also lay large numbers of eggs at a single time on the underside of leaves or on non-host plant substrates, where they can easily be carried between locales by human transportation. For the most part, a significant impact of the large yellow underwing on native or horticultural production in North America has not been recognised, though a number of authors have suggested that this species' generalist diet may lead to any such impact going unnoticed.

The Azorean Noctua atlantica, copyright Jens Jacobasch.

Historically, a large number of species have been included at one time or another in the genus Noctua, but a revision of this and closely related genera by Beck et al. (1993) cut it down on the basis of larval and male genital morphology to just two species. The only other species retained in Noctua sensu stricto by Beck et al. was N. atlantica, a species endemic to the Azores islands west of Portugal. Noctua atlantica is somewhat smaller than N. pronuba with duller hindwing coloration. It is restricted in its home range to the laurisilva, a particular subtropical forest type dominated by laurels and other evergreen, broad-leaved trees. Noctua pronuba is also found on the archipelago but inhabits are wider range of habitats. Genetic comparisons between the two species suggest that their populations diverged about five million years ago, a time frame that is not inconsistent with the origin of the Azores archipelago about four million years ago (Montiel et al. 2008). Perhaps an early population of N. pronuba became isolated on the Azores long enough to evolve into a distinct species, followed by a later re-colonisation of N. pronuba from the mainland. This would be similar to patterns seen in my home country of New Zealand, where repeated immigrations from Australia have lead to species pairs such as the endemic takahe Porphyrio hochstetteri and the more widespread pukeko P. melanotus, or the endemic (now extinct) Eyles' harrier Circus eylesi and the modern swamp harrier C. approximans.

REFERENCES

Beck, H., L. Kobes & M. Aloha. 1993. Die generische Aufgliederung von Noctua Linnaeus, 1758 (Lepldoptera, Noctuidae, Noctuinae). Atalanta 24 (1–2): 207–264.

Copley, C. R., & R. A. Cannings. 2005. Notes on the status of the Eurasian moths Noctua pronuba and Noctua comes (Lepidoptera: Noctuidae) on Vancouver Island, British Columbia. J. Entomol. Soc. Brit. Columbia 102: 83–84.

Montiel, R., V. Vieira, T. Martins, N. Simões & M. L. Oliveira 2008. The speciation of Noctua atlantica (Lepidoptera, Noctuidae) occurred in the Azores as supported by a molecular clock based on mitochondrial COI sequences. Arquipélago 25: 43–48.

ID for Heather?

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I was recently contacted by Heather Adamson who wanted to know if I could identify the animal in the above picture. She photographed it on an old post in the region of West Coolup, south of Mandurah here in Western Australia. I can tell her that it is some form of Lepidoptera larva (in other words, a caterpillar) and it looks like it may be beginning to weave itself a cocoon. Beyond that, I couldn't say. Do any of my readers have a better idea of what it is than I do?

Update: I shared this post to the Western Australian Insects group on Facebook, and Daniel Heald has suggested that Heather's photo may show the pupa of a lymantriid moth Teia athlophora. This species constructs itself a loose, cage-like cocoon from its own irritant hairs. The male, when he emerges, is a fairly standard looking brown moth, but the female is fat and flightless with only tiny stubs of wings. She will continue to live in and around her pupal cocoon, awaiting visits from courting males.

The Brown Honeyeaters

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Brown honeyeater Lichmera indistincta, copyright JJ Harrison.

Honeyeaters are one of the first groups of birds likely to be noticed by newcomers to Australia (after the crows and magpies, of course). Though generally not large birds, they are active, noisy and often colourful. Individuals or small groups of them will almost invariably be seen around trees in flower, seeking out nectar and squabbling over access to the best blooms.

Here in Perth, one of the more common honeyeater species is the brown honeyeater Lichmera indistincta. This is one of the smaller honeyeaters and as such might be less commonly noted by the casual observer, but it is abundant nonetheless. The brown honeyeater is one of a genus of about ten species of small, slight honeyeaters with slender decurved bills found from the Lesser Sundas of Indonesia to New Caledonia and Vanuatu (Higgins et al. 2008). Lichmera indistincta is the only species found in continental Australia. Most of the species are locally more or less abundant though some have quite restricted ranges, being found only on specific islands. A few are considered near-threatened. Lichmera species are predominantly grey-brown or greenish in colour; perhaps the most strikingly coloured is the black-necklaced honeyeater L. notabilis of the island of Wetar in the Lesser Sundas, which is yellowish-olive above and yellow below, with a striking white throat patch outlined in black.

Indonesian honeyeater Lichmera limbata, copyright Lip Kee.

Lichmera honeyeaters occupy a wide range of habitats but often prefer to be in the vicinity of water, occupying river-side woodlands and stretches of mangroves. One subspecies of the silver-eared honeyeater L. alboauricularis olivacea has a distribution that closely follows river systems in northern New Guinea. Favoured food plants of the brown honeyeater in Australia include Myrtaceae such as Eucalyptus and Melaleuca, and Proteaceae such as Banksia and Grevillea. They will also take small insects and spiders; I suspect that the proportion of nectar to insects in the diet depends on the availability of the former. Nests are open cups constructed of plant matter such as grass and pieces of bark bound together with spider web and other fibres. Small clutches of one to three eggs are brooded by the female alone, taking about two weeks to hatch, though the chicks are fed by both parents. The call of the brown honeyeater, which can be heard year-round, has been rendered as 'sweet-sweet-quarty-quarty'.

Nectar, of course, is not a hugely nutritious food source per volume (being mostly water), and a small bird like a brown honeyeater has to feed fairly constantly to keep itself going. Even though its metabolism slows down when sleeping, a brown honeyeater will still lose about half a gram of body weight overnight (Collins 1981) which is pretty impressive when you consider that the entire bire only weighs about eight grams (imagine if the average lost five kilos every night...) To make up for this loss, the bird feeds most heavily in the early morning, as well as retaining water for the last half-hour or so before going to sleep. And so it is that the honeyeater gets through the night.

REFERENCES

Collins, B. G. 1981. Nectar intake and water balance for two species of Australian honeyeater, Lichmera indistincta and Acanthorhynchus superciliosis. Physiological Zoology 54 (1): 1–13.

Higgins, P. J., L. Christidis & H. A. Ford. 2008. Family Meliphagidae (honeyeaters). In: Hoyo, J. del, A. Elliott & D. Christie (eds) Handbook of Birds of the World vol. 13. Penduline-tits to shrikes pp. 498–691. Lynx Edicions: Barcelona.

The Mancos Saltbush: Life in the Badlands

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Mancos saltbush Proatriplex pleiantha, from here.

Proatriplex pleiantha, the Mancos saltbush, is arguably not much to look at. It never grows very large (only about half a foot in height) and though a single plant may produce a lot of flowers, they are not very showy. Nevertheless, this little fleshy-leaved annual is something of a survivor. It grows on badlands in only a few localities in northern New Mexico and southern Colorado, and may be the only vegetation to be found on the eroded clays that it calls home. It persists in this hostile environment by not persisting; instead, each individual plant will produce hundreds, if not thousands, of seeds during its short life that may lie dormant in the soil for several years, waiting for the flash of rain that will allow it to emerge.

The Mancos saltbush was first described in 1950; its vernacular name refers to the original collection locality near the Mancos River. It was originally described in the genus Atriplex, a diverse cosmopolitan assemblage of herbs and shrubs in the family Chenopodiaceae commonly known as saltbushes and oraches (the garden orache or mountain spinach A. hortensis has long been grown as a vegetable in Europe). However, right from the start it was considered distinctive enough to be placed in its own subgenus, later raised to the status of a distinct genus by Stutz et al. (1990). A molecular phylogenetic analysis by Kadereit et al. (2010) later confirmed that Proatriplex pleiantha is not a direct relative of Atriplex, instead being associated with other small North American Chenopodiaceae genera Grayia and Stutzia. Features distinguishing Proatriplex from true Atriplex include the succulent leaves, the flowers being borne in groups of three to seven in the axil of a single bract, and the presence of a five-segmented perianth around female flowers (Atriplex flowers are borne singly to a bract, and lack a perianth).

Because of its restricted range, the Mancos saltbush may be vulnerable to disturbances in its habitat; for instance, one of its main population centres in New Mexico is in close proximity to the Navajo coal mine. Nevertheless, this species is not currently listed by the US Fish & Wildlife service as being of concern, due to its being locally abundant in the areas where it does occur. Surveys of this species have been complicated by the dependence of its germination on suitable weather conditions: in years with little rainfall, it may appear to be almost absent, but the advent of a wetter year may prove otherwise. All it takes is a decent drop of rain, and you may see the badlands bloom.

REFERENCES

Kadereit, G., E. V. Mavrodiev, E. H. Zacharias & A. P. Sukhorukov. 2010. Molecular phylogeny of Atripliceae (Chenopodioideae, Chenopodiaceae): implications for systematics, biogeography, flower and fruit evolution, and the origin of C₄ photosynthesis. American Journal of Botany 97 (10): 1664–1687.

Stutz, H. C., G.-L. Chu & S. C. Sanderson. 1990. Evolutionary studies of Atriplex: phylogenetic relationships of Atriplex pleiantha. American Journal of Botany 77 (3): 364–369.

Who Knows Which Way the Water Flows?

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Dorsal and lateral views of specimens of Trenella bifrons, from Parkhaev (2001).

There is no question that the molluscs are one of the most significant groups of animals in the marine environment. And thanks to the production by many species of mollusc of a hard shell, they are also one of the best-known groups in the fossil record. A rich and detailed picture of molluscan evolution is available to us as far back as the earliest Cambrian. But, of course, the further back in time we go the more questions we have about what the picture means. And it is in the earliest part of their history that the picture becomes the most opaque.

The Trenellidae are part of that early picture. This family of molluscs is known from the early Cambrian (Parkhaev 2002). They are part of the assemblage of early molluscs referred to as the helcionelloids, whose overall position in the molluscan family tree is very much open to question. Helcionelloids are simple, more or less cap-shaped or cone-shaped shells that are usually also tiny. The type species of the Trenellidae, Trenella bifrons, for instance, is only about 1 to 1.5 millimetres along the longest axis, and only one-half to one millimetre tall (Parkhaev 2001). This all adds up to a general shortage of morphological details that might help us pin down which, if any, modern molluscan groups helcionelloids are connected to. Possession of a undivided dorsal shell has lead many to compare them to gastropods. Others have pointed to the monoplacophorans like the modern Neopilina. In both cases, though, the resemblance is fairly superficial and confirming things one way or another would depend on identifying features of the soft anatomy, such as torsion, that are difficult if not impossible to infer from features of the shell alone.

Within the helcionelloids, trenellids are characterised by having the lower rim of one end of the shell's long axis drawn out into a siphonal groove. It seems likely that this groove was somehow involved in the passage of water around the gill(s), but whether its position indicates the front end or the back end of the shell, and whether it was used to draw water in or expel water out, depends again on what each author expects its original soft anatomy to have been. Unfortunately, evidence for the latter in trenellids is almost completely non-existent; while muscle scars have been identified in some helcionelloids, they remain unknown for this family.

The Trenellidae are closely related to, and probably include the ancestors of, the Yochelcionellidae in which the siphonal groove become raised and closed ventrally, turning it into a snorkel-like structure (one yochelcionellid, Yochelcionella daleki, has been featured on this site before). However, comparing trenellids to yochelcionellids raises something of a question in my mind. In general, mollusc shells grow through secretion from the mantle around the shell's rim only, meaning that once shell growth has passed a certain section the mollusc usually cannot go back and rearrange it. Assuming that helcionelloids grew in the usual molluscan manner, surely yochelcionellids would have gone through a stage in their development before the lower part of the 'snorkel' was closed off where they looked a heck of a lot like a trenellid? Is it even possible to distinguish a mature trenellid from a juvenile yochelcionellid?

REFERENCES

Parkhaev, P. Yu. 2001. Trenella bifrons: a new helcionelloid mollusk from the Lower Cambrian of South Australia. Paleontological Journal 35 (6): 585–588.

Parkhaev, P. Yu. 2002. Phylogenesis and the system of the Cambrian univalved mollusks. Paleontological Journal 36 (1): 25–36.

Lasiobelba: the Oppiid Way

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Lateral view (minus legs) of Lasiobelba pontica, from Vasiliu & Ivan (2011).

The animal illustrated above is a typical representative of Lasiobelba, a cosmopolitan genus of oribatid mites. Lasiobelba includes over thirty species of the family Oppiidae (Ermilov et al. 2014), commonly recognised as the most diverse family of oribatids. Oppiids are inhabitants of soils, where they primarily feed on fungi. Distinctive features of Lasiobelba within the Oppiidae include the absence of costulae (thickened ridges) on the prodorsum, and the presence of nine to ten pairs of setae on the notogaster that are inserted in two or four subparallel rows. The bothridial setae (the large sensory setae near the corners of the prodorsum) may be spindle-shaped at the ends or linearly hair-like; the two bothridial morphologies are used to distinguish two subgenera Lasiobelba and Antennoppia, respectively.

As is common for oribatids, there doesn't seem to be much information available for this genus beyond taxonomic studies. Lasiobelba species are most diverse in tropical and subtropical regions, with few reaching colder parts of the world. When they described the species L. pontica from the Movile Cave in Romania, Vasiliu & Ivan (2011) noted that this genus was otherwise unknown from the country. They suggested that this species might represent a relict of a warmer era that had managed to survive in the stable environment of the cave system after inclement conditions had driven it from the surface.

REFERENCES

Ermilov, S. G., U. Ya. Shtanchaeva, L. S. Subías & J. Martens. 2014. Two new species of oribatid mites of Lasiobelba (Acari, Oribatida, Oppiidae) from Nepal, including a key to all species of the genus. ZooKeys 424: 1–17.

Vasiliu, N. A., & O. Ivan. 2011. New oppiid species (Acari, Oribatida, Oppiidae) from Romanian caves. Trav. Inst. Spéol. "Émile Racovitza" 50: 3–14.

Crabs in Rivers, Crabs in Trees

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Freshwater crab Potamon ibericum, copyright Philipp Weigell.

Crabs are among the most recognisable animals one can find at the sea shore; any child who spends time at the beach will soon come to recognise their brandished pincers and sideways walk. But, as has been discussed by this site before, crabs are not only a coastal phenomenon. In warmer parts of the world, it may be possible to find crabs some distance inland.

Interestingly enough, there is at least circumstantial evidence that crabs made their way into fresh water relatively recently. The Old and New Worlds are each inhabited by a completely independent lineage of freshwater crabs that presumably originated after these continents went their separate ways. In the tropical Americas, rivers and streams are home to the Trichodactylidae, close relatives of the marine swimming crabs of the Portunidae. In the Old World, comparable habitats shelter a distinctly freshwater lineage comprising the superfamilies Gecarcinucoidea and Potamoidea.

Freshwater purple crab Insulamon palawanense, copyright Jolly Ibanez.

The classification of Old World freshwater crabs has (as with almost every other taxonomic group on this planet) shifted around a bit over the years. Many older references will combine all the Old World freshwater crab families into the Potamoidea but some more recent authors have tended to restrict this latter group to a single family, the Potamidae. There are other families, such as the African Potamonautidae and Deckeniidae, whose position superfamily-wise appears to be debated. The differences between the superfamilies Potamoidea and Gecarcinucoidea are primarily expressed in the structure of the males' second gonopods, the modified legs that the crabs use in transferring sperm during mating (Brandis & Sharma 2005). In the Gecarcinucoidea, a basal projection of the second gonopod surrounds the main body like a funnel for much of its length, while the tendril-like distal projection past this funnel is grooved and open on one side. In the Potamidae, the covering projection is restricted to the dorsal side only, and the distal part of the gonopod forms a closed tube.

Socotra limestone crab Socotra pseudocardisoma, copyright Gaëtan Rochez.

The Potamidae are most diverse in the Oriental bioregion with over seventy of the nearly eighty recognised genera being found there (Yeo et al. 2008). A couple of genera are found in the Afrotropical region. Only one genus, Potamon, makes it to Europe with modern species found in Italy and the Baltic peninsula, though the fossil record indicates a broader distribution on this continent in the past (Klaus & Gross 2009). Potamids are found in all types of water bodies, from fast-flowing streams and rivers to calm lakes and ponds, though they are inhabitants of the littoral zone rather than deep waters. The distinctive species Socotra pseudocardisoma is found on semi-arid limestone uplands of (surprisingly enough) the island of Socotra. Crabs of this species spend most of their time sheltered within cracks and crevices in the rocks that remain reasonably cool and damp year-round; they only emerge to the surface to forage during the rainy season while the surface briefly holds pools of standing water (Cumberlidge & Wranik 2002).

Another unusual lifestyle is found in a recently discovered species of the family Potamonautidae. This species from the Usambara Mountains of Tanzania specialises in living in phytotelmata, pools of water that accumulate in hollows in trees (Bayliss 2002). Though phytotelmata allow the crabs to inhabit regions of the rainforest that might otherwise be off limits, they are not the most forgiving of habitats. The combination of their small size together with an accumulation of organic matter means that the water in them tends to be quite acidic, a definite problem for a crab that relies on its calcitic exoskeleton for protection. The crabs feed on snails found in litter of the rainforest floor, and emerge from their home hollows to hunt at night or on cloudy, wet days. After eating a snail, they carry its shell back with them to their phytotelma and drop it in. The lime from the snail shell helps to neutralise the acidity of the water in the phytotelma, as well as supplying much-needed calcium that the crab will itself absorb when the time comes for it to moult to a new exoskeleton.

REFERENCES

Bayliss, J. 2002. The East Usambara tree-hole crab (Brachyura: Potamoidea: Potamonautidae)—a striking example of crustacean adaptation in closed canopy forest, Tanzania. African Journal of Ecology 40: 26–34.

Brandis, D., & S. Sharma. 2005. Taxonomic revision of the freshwater crab fauna of Nepal with description of a new species (Crustacea, Decapoda, Brachyura, Potamoidea and Gecarcinucoidea. Senckenbergiana Biologica 85 (1): 1–30.

Cumberlidge, N., & W. Wranik. 2002. A new genus and new species of freshwater crab (Potamoidea, Potamidae) from Socotra Island, Yemen. Journal of Natural History 36: 51–64.

Klaus, S., & M. Gross. 2009. Synopsis of the fossil freshwater crabs of Europe (Brachyura: Potamoidea: Potamidae). N. Jb. Geol. Paläont. Abh.

Yeo, D. C. J., P. K. L. Ng, N. Cumberlidge, C. Magalhães, S. R. Daniels & M. R. Campos. 2008. Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater. Hydrobiologia 595: 275–286.

Delta Wasp

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Two views of the potter wasp Delta unguiculata, copyright Entomart.

Not so long ago, I found myself struggling with the challenge of identifying potter wasps. Potter wasps are close relatives of the social wasps, close enough that they are usually classified in the same family Vespidae, but they belong to a distinct lineage (the subfamily Eumeninae) of a more solitary bent, each female constructing its own individual nests in which to lay its eggs. The 'potter' part of their name refers to their preferred material for said nests which are sculpted from mud. Though they do not form the vexatious swarms that social wasps can, potter wasps still tend to be relatively large and impressive wasps, and like social wasps they are usually strikingly patterned in bold colours to give fair warning of their potentially painful stings.

Nevertheless, despite being the sort of thing that would be likely to attract interest, identifying potter wasps can be a definite challenge. For a large part of the twentieth century, eumenine genera were mostly divided very finely, with the features separating related genera often difficult to distinguish. Here in Australia, I found an approachable identification guide for most eumenines to be nigh on nonexistent. One potter wasp genus that I did successfully pull out, however, was Delta.

Female Delta campaniforme constructing a nest, from Brisbane Insects.

Delta is a genus of about fifty species of potter wasp found in warm regions of the Old World. At least one member of the genus, D. campaniforme rendalli, has become established in Florida after being introduced there from southern Africa (Menke & Stange 1986). Delta belongs to the Eumenes group of genera, in which the first segment of the metasoma (the petiole) is very long and slender. Distinctive features of Delta within this group include the second segment of the metasoma being relatively short with the associated tergum bell-shaped, and the males having the last segment of the antenna bent backwards to form a hook (Nguyen 2015). Females build their mud nests, which they stock with moth caterpillars, cemented to flattened surfaces such as the sides of buildings or along branches. The species introduced to North America possibly arrived in the form of a nest glued to some easily transportable substrate such as a shipment of lumber.

The names of Delta and many other Eumenes-group genera derive from the work of Henri de Saussure, who recognised a single genus Eumenes corresponding to this group but divided it into a number of sections that he labelled Alpha, Beta and so forth. Later authors raised these sections to the status of separate genera though some expressed the objection that Saussure may have never intended these alphabetical designations to be formal names at all. The validity of Saussure's 'genus-group names' was eventually settled by a decision of the International Commission on Zoological Nomenclature but authors such as Menke & Stange (1986) have continued to criticise the recognition of these difficult segregate genera, especially as, whereas the Eumenes group as a whole is probably monophyletic, many of its component genera may not be. Future classifications may yet see Eumenes gathering its prodigals back into the fold.

REFERENCES

Menke, A. S., & L. A. Stange. 1986. Delta campaniforme rendalli (Bingham) and Zeta argillaceum (Linnaeus) established in southern Florida, and comments on generic discretion in Eumenes s. l. (Hymenoptera: Vespidae: Eumeninae). Florida Entomologist 69 (4): 697–702.

Nguyen, L. T. P. 2015. Taxonomic notes on the genus Delta de Saussure (Hymenoptera: Vespidae: Eumeninae) from Vietnam. Animal Systematics, Evolution and Diversity 31 (2): 95–100.

Metereca: Crossing the Divide

The crowdfunding campaign for my research on New Zealand harvestmen is still active. So far we're about 25% of the way towards the goal! Please click on the link above, and do your part to support your favourite arachnologist.

Dorsal view and pedipalp of Metereca papillata, from Roewer (1935).

There can be little doubt that the continent with the least studied harvestmen fauna relative to its likely diversity is Africa. Africa is home to a wide range of harvestmen lineages, some of which are found nowhere else on earth, but many remain unrevised. Among these poorly known elements are numerous members of the family Assamiidae. Among these are the members of the genus Metereca, which I drew as the semi-random subject for this post.

The Assamiidae are a family of short-legged harvestmen found in tropical regions of the Old World: Africa, Asia and Australia. I've spoken enough in the past about the shadow of Carl-Friedrich Roewer that hangs heavy over harvestmen systematics. Recent years have seen a large amount of research being conducted on the harvestmen of the Neotropics, resulting in a vast improvement in our taxonomic understanding for that part of the world. The harvestmen of the Old World, unfortunately, are yet to attract the same attention. Assamiids were last extensively reviewed by Roewer in 1935. He divided them between 17 subfamilies but in the usual Roewerian way these were mostly based on fairly superficial features (numbers of subsegments in the leg tarsi, whether the palp femur has long spines or only short denticles, etc.) that may not be that significant. Staręga (1992) published a checklist of African harvestmen in which he synonymised assamiid 'genera' that Roewer had placed in separate subfamilies, thus implicitly synonymising the subfamilies they were tied to.

Metereca is a genus of about fifteen known species of assamiid found across Africa. Roewer (1935) placed it in his subfamily Erecinae, supposed features of which included simple claws and the absense of a pseudonychium (a 'false claw' between the two real claws) on the third and fourth tarsi, two subsegments in the first telotarsus, small denticles on the pedipalp femur, concealed spiracles, and no median spine on the front margin of the carapace. However, the Erecinae as defined in this way included genera from all three of the Old World continents. Considering that other harvestmen groups have turned out to have a strong correlation between geography and phylogeny, I'd be willing to put money on Roewer's Erecinae not being monophyletic.

That same doubt applies to Metereca (though I'm not sure I'd put money on it this time), which is one of the larger erecine genera currently recognised. Supposed features of Metereca include a lack of dorsal spines on the body, and a four-segmented first tarsus and two-segmented second telotarsus. Species have been assigned to this genus from widely separated parts of the continent: the Congo, Tanzania, Mozambique. But not only is this a genus defined primarily by the absence of features (always a bit suspect), but other groups of harvestmen have tended to show a division between western and eastern Africa. It would be worth someone's time in the future, I think, to confirm whether Metereca really does cross the divide that others don't.

REFERENCES

Roewer, C. F. 1935. Alte und neue Assamiidae. Weitere Weberknechte VIII. (8. Ergänzung der "Weberknechte der Erde" 1923). Veröffentlichungen aus dem Deutschen Kolonial- und Uebersee-Museum in Bremen 1 (1): 1–168, pls 1–9.

Staręga, W. 1992. An annotated catalogue of Afrotropical harvestmen, excluding the Phalangiidae (Opiliones). Annals of the Natal Museum 33 (2): 271–336.

Checker Mallows

The crowdfunding campaign for my research on New Zealand harvestmen is still active. So far we're about 25% of the way towards the goal! Please click on the link above, and do your part to support your favourite arachnologist.

Flowering spike of Sidalcea nelsoniana, copyright Rhiannon Thomas.

Regular readers may have noticed that it's been a bit quiet around here lately. The last few weeks at chez Christopher have been... hectic. I have been writing posts but not had the time to publish them. So over the next few days, you'll be seeing a bit of a run of short posts in quick succession. Keep your eyes out.

The handsome plant you see above is a representative of Sidalcea, a genus of about thirty species found in the north of Mexico and the western United States. Members of this genus are commonly known as checker mallows (apparently because of the pattern of veins on the petals of some species); in the British gardening trade, they are also known as prairie mallows. As indicated by their vernacular names, Sidalcea species belong to the mallow family Malvaceae, and are hence related to other flowering plants such as cotton or hibiscus. These affinities are also reflected by their genus name, which is a portmanteau of the names of two other genera of Malvaceae, Sida and Althaea. Checker mallows differ from other members of the Malvaceae in having flowers with stamens that separate from the stamineal column in two tiers, an inner and an outer ring.

Most species of checker mallow are herbs; a few may develop into subshrubs. The genus includes both perennial and annual species. Stems of checker mallows are mostly more or less erect though they are often basally reclining or decumbent towards the base;it is not uncommon for decumbent stems to become secondarily rooted into the ground and develop into spreading stolons (or 'rhizomes'). Flowers of checker mallows are usually various shades of purple; a small number of species have white flowers (or white forms may occur in usually purple species). Many species of this genus are supposed to be difficult to identify: hybridisation is not uncommon, and some species are quite plastic in their own right. Young plants may also have a quite different appearance, including differently shaped leaves, from mature plants.

Sidalcea campestris, photographed by Amy Bartow.

The primary monograph of Sidalcea was published by E. M. F. Roush in 1931. She divided the genus between three subgenera, two of which contained only a single species each with all the remainder placed in her subgenus Eusidalcea (since the publication of Roush's monograph, a third non-Eusidalcea species has been recognised). These species are all perennials that, among other features, lack the variation in leaf shape with growth seen in Eusidalcea. More recent molecular analyses have supported Roush's arrangement arangement (Andreasen & Baldwin 2003). However, they have not supported Roush's division of Eusidalcea into separate sections for the annual and perennial species; instead, it appears that one or the other habit (it is unclear which) has arisen multiple times.

Like other diverse plant genera found in the California region, Sidalcea has attracted a certain degree of research into its evolutionary dynamics. Comparison of evolutionary rates between species has found that, as might be expected, annual lineages evolve faster than perennial ones (Andreasen & Baldwin 2001). Most species within each life-history class appeared to evolve at similar rates to each other, except for three perennial species: the three non-Eusidalcea species referred to above. One of these species, Sidalcea stipularis (the only one not known to Roush in 1931) showed evidence of an unusually high evolutionary rate for a perennial; this species is restricted to a very small population (only a few hundred plants may exist in the wild) and may have been subject to a higher rate of effective genetic drift. In contrast, the other two species have diverged more slowly than expected. One of these species, S. malachroides, is a presumably slow-lived subshrub; the other, S. hickmanii, commonly germinates after fires from seeds that may have remained in the ground for a number of years. In both cases, the overall result is that particular genotypes may persist in the population longer than in species with a more rapid turnover.

Oregon checkerbloom Sidalcea oregana ssp. spicata, copyright Dcrjsr.

Another feature of Sidalcea population dynamics to have attracted interest is the occurrence in several species of gynodioecy, a phenomenon where some individuals of a population have flowers with both male and female organs whereas other individuals have female organs only. The persistence of such an arrangement raises questions: because hermaphroditic individuals have the potential to contribute to more reproductive pairings than female-only individuals, shouldn't the former end up out-competing the latter and eliminating them from the population? This has lead to the inference that some factor(s) must give the female-only individuals an advantage that allows them to persist. Ashman (1992) found in germination tests of Sidalcea oregana spp. spicata that seeds that came from female-only plants tended to germinate into healthier, more vigorous offspring than those from hermaphrodites. It may be that plants that can only produce seed by outcrossing are less vulnerable to the effects of inbreeding, or perhaps not having to invest energy in making pollen means that the parent can put more energy into producing seeds.

REFERENCES

Andreasen, K., & B. G. Baldwin. 2001. Unequal evolutionary rates between annual and perennial lineages of checker mallows (Sidalcea, Malvaceae): evidence from 18S–26S rDNA internal and external transcribed spacers. Mol. Biol. Evol. 936–944.

Andreasen, K., & B. G. Baldwin. 2003. Reexamination of relationships, habital evolution, and phylogeography of checker mallows (Sidalcea; Malvaceae) based on molecular phylogenetic data. American Journal of Botany 90 (3): 436–444.

Ashman, T.-L. 1992. The relative importance of inbreeding and maternal sex in determining progeny fitness in Sidalcea oregana ssp. spicata, a gynodioecious plant. Evolution 46 (6): 1862–1874.

Roush, E. M. F. 1931. A monograph of the genus Sidalcea. Annals of the Missouri Botanical Garden 18 (2): 117–244.

New Zealand Harvestmen: Please Help

The cave-dwelling Forsteropsalis photophaga, a remarkable harvestman species described in Taylor & Probert (2014).

As regular readers of this blog will be well aware, I've been working for several years now, off and on, on the taxonomy of long-legged harvestmen of the family Neopilionidae from Australia and New Zealand. In the past few years, this has been a bit more off than on: the necessities of earning a crust have meant that I haven't had the time to dedicate to full-time harvestman research. Nevertheless, I've been putting things together here and there where I can and an enormous amount of progress has been made. Back when I first decided to investigate this group of animals in 2000/2001, there were a handful of named species, often with descriptions amounting to nothing more than a couple of vague lines, all but unidentifiable in practice. Over time, I've redescribed each of these species in turn, as well as describing and naming a pile of new ones. We've learnt things about these animals we never knew before, such as the presence in many populations of a remarkable divergence within males to the extent that to the uninitiated they might be (and have been) mistaken for completely different species. We've seen the incredible range of forms in this group, from long-jawed monsters like to one at the top of this post, to heavily armoured cryptic soil-dwellers like in this photo by Stephen Thorpe.

After many years, I feel I'm finally approaching the point where I can put the finishing touches on my revision of the New Zealand neopilionids (for a given value of 'finish', of course, because there is no group of organisms for which the work is ever truly finished). Ideally, I would like to publish something incorporating a complete overview of this group of animals, a complete guide to all the known species offering a one-stop-shop to allow anyone, anywhere to confidently identify any specimen that might come to their hand. It's also important to me that I publish this guide in an open-access format so that it's also available at any time.

But to do that, I need your help. In order to be able to travel to the New Zealand museums that hold types and other crucial specimens that I need to examine, and to cover the publication fees of the resulting product, I've started a crowdfunding drive. Head over to https://experiment.com/projects/how-can-we-distinguish-species-of-new-zealand-harvestmen and you'll be able to support my research, follow the results as they become available, and receive full acknowledgement in the resulting publication(s). Even if you can't support me directly myself, you would be helping immensely if you inform others of my campaign, whether through social media, in person, or any other medium that makes itself available. Together, we can bring this truly incredible group of animals the recognition they so richly deserve!

If you want to see some of my work on harvestmen that's already come out, check out the links below:

Remarkable things
Possibly the coolest thing I had published this year
Score one for biogeography
How to wipe out a family
The saga of Forsteropsalis fabulosa
More on the New Zealand Opiliones
Bye, bye, Spinicrus
The eater of light
New Zealand fills a biogeographical gap

Gazelles and their Kin

Female steenbuck Raphicerus campestris, copyright Yathin S. Krishnappa.

Ever since biblical times, gazelles have been a byword for a kind of watchful elegance, always on guard against unwanted advances. It is not difficult to see how such an analogy arose: on their native savannah, gazelles are indeed always on the alert, wary of the threat of predators and quick to respond to alarm. It is a habit that has served them for millions of years.

The Antilopini are an assemblage of about thirty species of mostly smaller antelope found in Africa and Asia*. The smallest are the dikdiks of the genus Madoqua which may be only a foot or so in height and weight just a few kilos; the tallest, the dibatag Ammodorcas clarkei, stands about 90 cm at the shoulder and weighs about 30 kilograms. They are mostly associated with arid or semi-arid habitats: savannahs, deserts, steppes and the like. Some species form sizeable herds; others live solitary lives.

*Before I go too much further, I should note that J. K. Revell over at his site Synapsida has written a number of posts about bovids (antelopes, cattle, etc.) over the the past few years that I heartily recommend. To the best of my knowledge, he hasn't gotten to antilopins yet, so I should be safe on that front.

Female and male oribi Ourebia ourebi, copyright Bill Higham.

Modern researchers largely agree on dividing the Antilopini between four major lineages, recognised as subtribes. One contains a single species, the oribi Ourebia ourebi, a smaller species with short, straight horns found in eastern sub-Saharan Africa. The Raphicerina, including the dikdiks Madoqua, the steenbucks and grysbucks Raphicerus and the beira Dorcatragus megalotis, are similar small, short-horned species. The Raphicerina and oribi are solitary species with individuals maintaining exclusive territories (at least between members of the same sex). They advertise their territories through the use of defecation sites together with the marking of vegetation using scent glands in front of the eye. The Raphicerina are exclusively browsers, concentrating on higher-quality food sources; in contrast, the oribi is a grazer and consequently must occupy a larger territory than the other species. Females of Raphicerina and oribi are hornless; in most other Antilopini (with some exceptions noted below), horns are present in both sexes though the females' horns are shorter and more slender.

Przewalski's gazelles Procapra przewalskii, copyright Yilun Qiao.

The majority of the remaining Antilopini live in herds though males of most species will claim temporary territories during the breeding season as they attempt to gather harems of females. The central Asian gazelles of the genus Procapra are placed in their own subtribe; these are three pale, medium-sized species found on steppes and high-altitude grasslands between the Himalayan plateau and Mongolia. They have rear-swept horns that make them look a bit like a gazelle that is trying to pass itself as a goat. Procapra gazelles may not be immediately related within the Antilopini to the true gazelles in the largest of the four subtribes, the Antilopina. Until recently, most authors would have treated the great majority of the Antilopina species in the genus Gazella; however, questions about the monophyly of this genus in the broad sense have lead to the recognition of three separate genera of gazelles: Gazella sensu stricto, Nanger and Eudorcas. The Nanger species, which include the dama gazelle N. dama and Grant's gazelle N. granti, are relatively large gazelles with a conspicuous white rump that is absent in the other two genera. The genus Eudorcas includes perhaps the most familiar gazelle species, Thomson's gazelle E. thomsoni of Kenya and Tanzania, which forms much larger herds than other gazelle species.

Mhorr gazelles Nanger dama mhorr at Tierpark Hellabrunn in München, copyright Rufus46.

The remaining living Antilopina species are all placed in their own separate genera. The springbuck Antidorcas marsupialis of southern Africa also forms large herds that used to number in the tens of thousands before hunting and habitat loss reduced their population. Springbucks are best known, of course, for their habit of 'pronking', a mode of bounding with all four legs held stiff and landing simultaneously, most often seen when the animal is alarmed or at play. Pronking is not unique to springbucks (other gazelles do it too) but it is made particularly noticeable in this species by a crest of white hairs towards the rear of the back that is erected at the same time.

Springbuck Antidorcas marsupialis engaged in some pronking, copyright Hans Stieglitz.

In other species of Antilopina, only the males have horns. The gerenuk Litocranius walleri and dibatag Ammodorcas clarkei are two slender species found in eastern Africa that differ from other Antilopina in being browsers rather than grazers and maintaining permanent exclusive territories. Both these species habitually feed while standing erect on the hind legs, allowing them to browse at higher levels than they could otherwise; they are even able to walk about to a certain extent in this pose, albeit perhaps not in a manner that could be called graceful. Outside of Africa, the blackbuck Antilope cervicapra is found in grasslands and woodlands of the Indian subcontinent (there is also supposed to have been a small introduced population of them near Geraldton here in Western Australia, though it may have since been eradicated). Males of this species have long, spirally twisted horns; mature males are also the only 'blackbucks' that are actually black (at least dorsally) whereas females and young males are light brown.

Pair of juvenile dibatags Ammodorcas clarkei at a rescue centre, copyright F. Wilhelmi.

Perhaps the most distinctive member of the Antilopina, however, is the saiga Saiga tatarica. This is the only species that is known to never be territorial, forming large herds in its native habitat of the central Asian steppes (technically, the social habits of the little-studied dibatag are largely unknown but it would not be unreasonable to presume that they are similar to those of the gerenuk). It is more robust than other Antilopina species; indeed, there was long uncertainty about whether saiga are more closely related to gazelle or goats. The nostrils of saiga are inflated to a hanging proboscis that is usually presumed to function as protection for the respiratory tissues from the dust of their near-desert habitat. However, there may also be a display function involved; during the mating season, the proboscis of males becomes engorged while scent glands in front of the eyes produce pungent secretions (so maybe the function of the proboscis is actually to somehow protect the saiga from its own stench). Unfortunately, the saiga (among other Antilopini species) is currently regarded as critically endangered, with only a fragment of its historical population surviving. There was a time when the saiga was thought to be something of a conservation success story: after being almost wiped out in the early 1900s, populations built up to about two million by the 1950s. But in the last few decades, the combined effects of factors such as habitat loss, disease and the demand for their horns from everyone's favourite country to turn the extermination of endangered species into a pointless investment bubble have caused numbers to crash back down to an estimated 50,000 or so (as relayed by Wikipedia).

Pair of saiga Saiga tatarica, copyright N. Singh.

Fossil species have been assigned to the genus Gazella from as far back as the Miocene though there may be grounds for debating how many of them are true Gazella. For instance, Bärmann (2014) commented on preliminary results of a phylogenetic analysis including the Pakistani Miocene species G. lydekkeri (from the well-studied Siwalik deposits) that suggested that it might be placed outside the Antilopina crown group. Other fossils of Antilopini inform us that the modern blackbuck is the sole survivor of a lineage of spiral-horned antelopes that was previously more widespread in Eurasia. The saiga was more widespread in the past as well, with either the modern or a closely related species known during the Pleistocene from more northerly parts of Siberia (at which point, presumably, there may have been saiga in the taiga) and even in northernmost North America. If they do disappear completely, it will be a sad end to a long history.

REFERENCES

Bärmann, E. V. 2014. The evolution of body size, horn shape and social behaviour in crown Antilopini—an ancestral character state analysis. Zitteliana B 32: 185–196.

Macdonald, D. (ed.) 1984. All the World's Animals: Hoofed Mammals. Torstar Books: New York.

Peering through a Limpet's Keyhole

Keyhole limpet Fissurella latimarginata, copyright Jan Maximiliano.

In an earlier post, I introduced you to the slit limpets, conical- or flat-shelled gastropods in the family Fissurellidae that possess a longitudinal slit at the front of their shells in order to help achieve the imposrtant condition of having one's anus as far away from one's mouth as possible. The image above shows another member of the same family, but this time known as a keyhole limpet. In the keyhole limpets of the genus Fissurella, the slit has been closed off and modified into a rounded opening bound by a callus at the shell's apex. The apex is located sub-centrally on the shell which is also radially ornamented (Simone 2008). Other interesting features of the genus include a tendency for the radula to be asymmetrical with the three- or four-cusped lateral teeth larger on one side than the other. Two related genera, Amblychilepas and Macroschisma, differ primarily in having larger soft bodies that cannot be retracted under the shell whereas Fissurella species are able to seal themselves in (Aktipis et al. 2011).

Fissurella volcano, copyright Jerry Kirkhart.

Various Fissurella species are found around the world. They have been divided between several subgenera, but Fissurella taxonomy is complicated by the fact that the overall shape of the shell is strongly affected by the nature of the substrate each individual makes its home. Truly reliable identification of distinct taxa requires detailed knowledge of the soft anatomy which is apparently still little-known for many species. According to Simone (2008), there is a correlation between shell height and energy level of each species' preferred habitat: species found in higher-energy environments (such as shorelines subject to heavy surf) tend to have higher shells (which surprises me because, if you'd asked me to guess, I might have expected the opposite).

As far as humans are concerned, though, most keyhole limpets have fairly little economic impact. Larger species, which can get up to about ten centimetres in size (many are much smaller), are harvested for food around the coast of South America. I also came across a reference to a Fissurella species being regarded as a pest in abalone aquaculture, as both species are algae-grazers and compete for food. Other than that, one imagines that their pre-perforated shells could be very useful for children wanting to make a (possibly somewhat malodorous) necklace as a souvenir of a trip to the beach.

REFERENCES

Aktipis, S. W., E. Boehm & G. Giribet. 2010. Another step towards understanding the slit-limpets (Fissurellidae, Fissurelloidea, Vetigastropoda, Gastropoda): a combined five-gene molecular phylogeny. Zoologica Scripta 40: 238–259.

Simone, L. R. L. 2008. A new species of Fissurella from São Pedro e São Paulo Archipelago, Brazil (Vetigastropoda, Fissurellidae). Veliger 50 (4): 292–304.

Sunorfa

The Queensland pselaphine Sunorfa nigripes, from Chandler (2001).

When I began researching the taxon that was to be the subject of this post, I was surprised to discover that it had weaseled its way onto this site once before. Back in the day, I used an example of the beetle genus Sunorfa to illustrate a post about a closely related genus for which I had been unable to find an image (before a reader pointed me in the direction of one). Sunorfa is a member of that wonderful group of miniature gargoyles, the Pselaphinae (I had the pleasure/pain of sorting a handful of pselaphines at work just the other week; their minute size [usually only a millimetre or two long] makes them a real challenge to work with but their bizarre morphologies make it impossible to resent them). Most species of Sunorfa are found in tropical rainforest litter in southern Asia and Australasia from Sri Lanka to Fiji with the highest diversity of species in New Guinea. In addition, a handful of species are found in the Seychelles. I haven't come across any direct indication of what Sunorfa are doing in all these places but presumably, like other pselaphines, they are predators of even smaller arthropods.

Distinctive features of Sunorfa compared to other pselaphines include a strong transverse sulcus (groove) across the rear part of the pronotum, and a cylindrical abdomen in which the upper tergites and lower sternites are fused into single continuous rings. They also have characteristic foveae (deep depressions) on the top of the head, the base of the elytra including on each side at the 'shoulders', and in the middle of the metasternum (the rear underside section of the thorax) (Chandler 2001). Similar foveae are found in one form or another, in one place or another, on most pselaphines. They have received a lot of attention in taxonomic studies (their appearance and distribution is one of the most reliable features in distinguishing pselaphine taxa) but their function is less well known. Chandler (2001) expressed the opinion that foveae in different parts of the body serve different purposes. Those on the thorax have solitary, sensilla-like setae at their centres and probably represent sensory structures of some kind. Conversely, foveae on the head and abdomen lack such setae and commonly connect to one another internally to form solid tubes. These tubes may function as struts, providing the body with rigidity and strength as the animal is reduced down in size.

REFERENCE

Chandler, D. S. 2001. Biology, morphology, and systematics of the ant-like litter beetle genera of Australia (Coleoptera: Staphylinidae: Pselaphinae). Memoirs on Entomology, International 15: 1–560.

All that is Silver is not Fish

Common silverfish Lepisma saccharina, copyright Christian Fischer.

The insects are deservedly recognised as one of the most successful groups of organisms on the planet. Thanks in no small part to their unlocking the ability of flight, insects can be seen today in almost every part of the planet above sea level. But not all insects, of course, are flighted; many remain firmly on the ground. A large proportion of these are the descendents of flighted ancestors that returned to a terrestrial existence but there are also some whose ancestors never took to the skies. For most people, the most familiar of these original land-huggers are likely to be the silverfish of the family Lepismatidae.

Silverfish are long-bodied insects with a covering of reflective scales—hence the 'silver' part of their name. The 'fish' part probably refers to the manner of their movement; speaking from my own experience collecting them, these buggers move fast, slipping along the ground like a silver minnow. There are over 250 known species of Lepismatidae (Mendes 2002); probably many more remain to be described. They comprise over half the known species of the insect order Zygentoma (sometimes referred to as the Thysanura though most current entomologists tend to avoid that name due to its previous history referring to a now-obsolete grouping of the Zygentoma with the superficially similar Archaeognatha); the other families in the order are commonly subterranean and less commonly encountered by the average person. The highest diversity of silverfish occurs in tropical and subtropical parts of the world, particularly in arid or semi-arid regions. Adaptations of the rectal epithelium allow silverfish to absorb moisture straight from the atmosphere (or, to put it another way, they drink through their butt), making them ideally suited to tolerating the dryness of deserts. They are also suited to tolerating the relatively dry habitats offered by the interiors of human houses and several species have become our associates (in cooler parts of the world, these synathropic species are often the only lepismatids around). These include the common silverfish Lepisma saccharina and the giant silverfish Ctenolepisma longicaudata. The firebrat Thermobia domestica is a colourfully patterned human associate that likes it particularly warm; it is usually restricted to places like the backs of stoves or alongside hot-water cylinders where it can find the heat it craves. Being detritivores (that is, they feed on dust), human-associated silverfish are usually quite innocuous though they may cause problems if their numbers get too high or if they get into stored foodstuffs.

Firebrat Thermobia domestica, copyright David R. Madison.

In areas where they are native, silverfish may be quite diverse. Watson & Irish (1998) conducted a study of an area of the Namib Desert that was home to eight different species of silverfish. They found a tendency for the species to differ in their preferred microhabitat within the area: some were restricted to the upper parts of the sand dunes dominating the region, others were restricted to the rocky hollows separating the dunes. Those found in rocky lower zones resembled the familiar human-associated species (indeed, they included members of the same genus as the giant silverfish, Ctenolepisma) in being elongate and slender. In contrast, those species found higher in the dunes themselves were shorter and more flattened with well-developed spines covering the legs. These features allowed the dune silverfish to effectively 'swim' through the sand, using the spines on the legs to dig about and their flattened form to slip between grains.

REFERENCES
Mendes, L. F. 2002. Taxonomy of Zygentoma and Microcoryphia: historical overview, present status and goals for the new millennium. Pedobiologia 46: 225–233.

Watson, R. T., & J. Irish. 1998. An introduction to the Lepismatidae (Thysanura: Insecta) of the Namib Desert sand dunes. Madoqua 15 (4): 285–293.

Forams with Teeth

Time for another foram post. The above image (copyright Robert P. Speijer, scale bar = 100 µm) shows Turrilina brevispira, a typical Eocene representative of the foram subfamily Turrilininae.

The Turrilininae are a group of calcareous forams that first appeared in Middle Jurassic (Loeblich & Tappan 1964). In most species, the test is what is called a 'high trochospiral' form: that is, it coils in a similar manner to, and overall looks rather like, a high-shelled snail. Each of these whorls is divided into at least three successive chambers, sometimes more. At the end of the test is a loop-shaped aperture. At least one species of turrilinine, Floresina amphiphaga, is a predator/parasite of other forams, drilling into their test to extract their protoplasm.

The turrilinines are most commonly classified in a broader foram superfamily known as the Buliminoidea or Bulimnacea. Other buliminoids commonly resemble turrilinines in their overall form. The group has commonly been defined, however, on the basis of what is called a 'tooth-plate'. This is an outgrowth of the internal wall of the test that runs between the apertures of each chamber. The exact appearance of the tooth-plate differs between taxa; in Turrilina, for instance, it is a trough-shaped pillar that is usually serrated along one end (Revets 1987). I have no idea what the function of the tooth-plate is, if indeed any is known, whether it provides an anchor for some cytoplasmic structure or anything else. However, in more recent decades a number of authors have questioned whether the tooth-plate is as significant a taxonomic feature as previously thought. For instance, Tosaia is a Recent genus of foram whose overall morphology and chamber arrangement is fairly typical for the Turrilininae but which lacks any sign of a tooth-plate (Nomura 1985). Excluding Tosaia from the buliminoids on this basis alone would imply a remarkably strong evolutionary convergence of every other feature of this genus.

REFERENCES

Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida vol. 2. The Geological Society of America and the University of Kansas Press.

Nomura, R. 1985. On the genus Tosaia (Foraminiferida) and its suprageneric classification. Journal of Paleontology 59 (1): 222–225.

Revets, S. A. 1987. A revision of the genus Turrilina Andreae, 1884. Journal of Foraminiferal Research 17 (4): 321–332.