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?

The deadine for my crowdfunding drive has been extended. Thanks to your support, I am over 40% of the way towards success! But I'm still going to need everyone's help if I'm to be succesful. Please visit my page at Experiment.com and consider offering your support!

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.