A new marine goby from the Fiji Islands, Eviota karaspila, has recently been described in a paper in Zootaxa.
The specific name is an adjective derived from the Greek kara (head) and spilous (spot), referring to the distinctive spot on the occiput (upper head). The suggested common name of Eastern headspot pygmy goby also reflects this characteristic marking. On the basis of the type material this fish grows to about 1.8cm/0.75in, so it really is a pygmy species.
There are, however, a number of Eviota species – eg. E. melasma and E. smaragdus, close relatives geographically speaking – which exhibit a similar spot but differ in their overall live coloration, and, it turns out, their form. Comparison has now revealed slight differences in morphometrics (standard counts and measurements used when describing fishes) although visually these species look similar in shape.
The authors of the paper point out that earlier workers on this goby genus did not have access to colour photographs of live specimens and worked entirely from preserved material. Many features of live coloration disappear when a fish is dead and preserved, leaving only dark markings visible. This means that species which are quite obviously distinct when alive may look identical when preserved and be mistakenly considered the same species.
It appears that morphometric characters have hitherto been somewhat neglected when comparing Eviota species and the authors suggest that in view of the similarity in markings in dead material, more attention should be paid to differences in body proportions in future.
For further details see: Greenfield, D. W. & J. E. Randall (2010) Eviota karaspila, a New Gobiid Fish from Fiji (Teleostei: Gobiidae). Zootaxa 2672: 61-68.