Field of Science

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.


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.


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.


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.