This is the first of two articles looking at the language we use around fish records and taxonomy. Here, I’m looking at what we mean by native, endemic, undescribed and newly described. In the second article, I turn to distribution – new records, range extensions and what happens when a fish turns up somewhere we did not expect it.
[The second article is here: When the map changes.]
One of the hazards of writing about fish is that the names have an irritating habit of moving underneath you. A fish I once knew as the smoky chromis or smoky puller, Chromis fumea, is a very good example.
For years, Chromis fumea was considered to have a remarkably wide and rather disjointed distribution across the western Pacific, including Norfolk Island. Then, in 2021, fish taxonomists Gerald and Mark Allen took a closer look. It turned out that what had been called Chromis fumea was not one species after all. Their study found a complex of closely related species. Chromis fumea is now considered to occur mainly around Japan and Taiwan, with occasional records farther south. The northwestern Australian fish was described as another new species, Chromis sahulensis. And the fish from our part of the southwestern Pacific became Chromis norfolkensis – the Norfolk chromis.
Courtship colours of the Norfolk chromis, Chromis norfolkensis
Groups can be found in the mid-water column
This wasn’t really a name change; the fish hadn’t changed, of course. What changed was our understanding of which fish belonged to which species.
There is an especially nice Norfolk connection to Chromis norfolkensis, because the holotype – the specimen formally chosen to anchor the name of the new species – was collected at Duncombe Bay, Norfolk Island, on 21 November 1989 at a depth of 18 metres. Presumably, this specimen had been sitting in a museum collection for more than 30 years before becoming the holotype of the newly described species. The species name norfolkensis is a nod to that type locality.
But here is the first potential trap: Chromis norfolkensis is not endemic to Norfolk Island. It is also known from northern New Zealand, New Caledonia and the Chesterfield Islands, with photographic records also from New South Wales.
Having Norfolk in a scientific name does not mean a species occurs only here. Sometimes it simply tells us where the specimen used in its original description came from.
Chromis fumea and Chromis norfolkensis are similar enough that they spent decades being regarded as the same species. Both have brownish colouring above and paler colouring below, dark bands on the upper and lower margins of the tail and a small white spot near the rear of the dorsal fin.
Once you know what to look for, however, there are differences. The adult Chromis norfolkensis is distinctly two-toned. The upper part of the fish is brown to yellowish brown and the lower part is white. The boundary between the two is relatively abrupt, running slightly diagonally backwards from the eye towards the small white spot near the rear of the dorsal fin.
In C. fumea, the brown upper body grades much more gradually into the paler underside. The lower body can also show yellowish-brown edging on the scales, giving it a more yellow-striped appearance.
The fins provide other clues. The anal fin of C. norfolkensis is predominantly white, while that of C. fumea is blue. Both have dark bands along the tail, but the overall colour pattern is cleaner and more sharply divided in C. norfolkensis.
Then there are the characteristics that I am unlikely to establish from one of my underwater photographs. C. norfolkensis generally has more gill rakers on the first gill arch than C. fumea.
On top of all that, the two recognised species are separated by thousands of kilometres.
Interestingly, Allen and Allen did not have DNA sequence data for C. norfolkensis when they described it. Their conclusion was based on morphology, colour pattern, counts such as the gill rakers, and geography. DNA is an extremely useful taxonomic tool, but it is not the only way in which species are recognised.
All of which brings me to some words I use regularly on this website.
A quick guide to the terminology
Native – a species that occurs here naturally, rather than having been introduced by people. It can also occur in many other places.
Endemic – a species naturally restricted to a defined geographical area. If we say something is ‘endemic to Norfolk Island’, its known natural distribution is Norfolk Island and nowhere else. The geographical bit is important: a species can instead be endemic to a larger region.
Undescribed species – an organism believed to represent a species that has not yet been formally described and named. It may already be known to scientists, photographed or sitting in a museum collection. ‘Undescribed’ does not mean ‘endemic’.
Newly described species – a species for which the formal scientific description has now been published. The organism itself may have been known for decades. Chromis norfolkensis, formally described in 2021 from specimens collected much earlier, is a good example.
Type locality – the locality associated with the specimen or specimens on which a species was originally based. Being the type locality does not mean the species is endemic there.
Holotype – the single specimen formally designated as the name-bearing specimen for a species when it is described.
Species split – when evidence shows that organisms previously treated as one species actually represent two or more distinct species. The Chromis fumea story is an example.
Norfolk Island blenny, Parablennius serratolineatus
Something that really is endemic
Norfolk Island blenny, Parablennius serratolineatus, among sea urchin spines
The Norfolk Island blenny, Parablennius serratolineatus, is a great example.
It was formally described in 1986 and its type locality is Point Hunter at Emily Bay. Its known distribution remains Norfolk Island. As far as current records show, this little fish occurs nowhere else on Earth. For a Norfolk endemic, our reef is the total global distribution.
I regularly see them sheltering in shallow reef habitat, sometimes tucked among sea urchin spines. They are tiny – the published maximum standard length is only about 3 cm – and easy to overlook until you know they are there.
That does not automatically make an endemic species threatened. Abundance, population trends, life history, habitat requirements and other factors have to be considered as well. But a species with its entire geographical range concentrated around one small island starts from a very different position from a fish distributed right across half the Pacific. Small blips affecting its tiny home habitat can have catastophic effects to its population numbers.
Then there are the fish that don’t have names yet
I have another very small fish in mind when I think about all this – an Eviota, one of the dwarfgobies.
It appears that it may represent an as-yet undescribed species. An undescribed species is not automatically a new species until the work required to establish that it is has been done. Nor is it automatically endemic.
Someone, a researcher, needs to compare it carefully with its relatives and determine whether there are consistent characteristics separating it from already described species. Depending on the circumstances, that may involve morphology (the physical form, shape, size, and structural features of organisms, including both outer appearance and inner body parts), colour pattern, genetics and other evidence. A formal description then needs to be published and type material designated.
Even if the fish does prove to be a separate species, we still have another question. Where else does it live? It may eventually turn up at Lord Howe, New Caledonia, the Kermadecs or somewhere much farther afield. Or perhaps it really does occur only at Norfolk Island.
For now, for the little Eviota I mentioned, ‘apparently undescribed and possibly endemic’ is as far as I am prepared to go.
However, there is already a wonderful Eviota precedent here. On 17 February 1991, John Randall and Malcolm Francis collected two tiny gobies from a cave near Bombora Rock in Sydney Bay. The male was just 13.4 mm long and the female 12.7 mm. More than 26 years later, in 2017, David Greenfield and John Randall formally described them as Eviota lentiginosa, the freckled dwarfgoby. The species is still known only from Norfolk Island, and as yet there are no images of this fish on iNaturalist.
Those two tiny fish spent more than a quarter of a century existing as specimens in a museum before acquiring a formal scientific name.
I rather like that when thinking about the little Eviota I am now photographing. Perhaps it has a similar story ahead of it. Perhaps someone will eventually tell me it is something already known from elsewhere.
Either result gives us more information than we had before.
Between them, these fish cover quite a bit of taxonomic territory. The Norfolk Island blenny is, on present evidence, endemic. Eviota lentiginosa is a formally described species known only from Norfolk Island. Another Eviota may be undescribed and may eventually prove endemic. Chromis norfolkensis was recognised only after a species split and, despite its name and Norfolk Island holotype, is not endemic here.
So while the fish have been there all along, we are still working out exactly what they are and where they are found apart from here.
This article is the first of two parts. In the next, I’ll turn from what a species is called to where we think it lives – and how new records can redraw those boundaries.
Eviota, one of the dwarfgobies, possibly as yet undescribed
References
Allen, G. R., & Allen, M. G. (2021). Two new species of Chromis (Teleostei: Pomacentridae) from northwestern Australia and the southwestern Pacific Ocean, previously part of C. fumea (Tanaka, 1917). Journal of the Ocean Science Foundation, 38, 78–103. https://doi.org/10.5281/zenodo.5601971
Bath, H., & Hutchins, B. (1986). Die Blenniini des australischen Raums und Neuseelands mit Beschreibung einer neuen Art und einer neuen Unterart. Senckenbergiana Biologica, 66, 167–213.
Francis, M. P. (1993). Checklist of the coastal fishes of Lord Howe, Norfolk, and Kermadec Islands, southwest Pacific Ocean. Pacific Science, 47(2), 136–170.
Greenfield, D. W., & Randall, J. E. (2017). Eviota lentiginosa, a new dwarfgoby from Norfolk Island, Australia (Teleostei: Gobiidae). Journal of the Ocean Science Foundation, 29, 66–71. https://doi.org/10.5281/zenodo.1117964