The genus Pseudocoris has received a full taxonomic review by Benjamin C. Victor, Allan D. Connel and John E. Randall. The paper includes a description of two new species from the Indian Ocean, Pseudocoris hemichrysos & P. occidentalis, both of which are the corresponding sisters to their Pacific Ocean counterparts. This brings the total number of scientifically recognized species to nine.
Pseudocoris is a genus of planktonic feeding labrids more affectionally known as Torpedo Wrasses. This name is aptly given for the speed at which they peruse their habitat, making capture and photography extremely frustrating. Pseudocoris‘ evolutionary offshoot from Coris is quite clearly seen, but unlike their preference for benthic prey, the former has evolved to pick zooplankton from the water column. As such, they have lost the strong canine teeth associated with a diet corresponding to hard shelled invertebrates.
Instead, Pseudocoris possess smaller anterior canines and forward facing eyes best suited for their planktivorous diet. Prior to this paper, seven species of Pseudocoris were known. But like many widely distributed species, the divide between the Indian and the Pacific Oceans harbour geminate twins that are very often taxonomically distinct. In this paper, the previously dual-oceanic Pseudocoris yamashiroi and Pseudocoris heteroptera have been split, with the Indian Ocean populations now regarded as Pseudocoris hemichrysos and Pseudocoris occidentalis, respectively.
This brings the total species count for the genus to nine, with three geminate pairs and three regional endemics of the Pacific Ocean.
Pseudocoris occidentalis is known from a male holotype collected in Mombasa, Africa. The terminal males of this species are various shades of malachite, generally fading to a lighter ventral region. The anterior portion of the head and body is encapsulated in an inky blue-black, breaking up into vertical stripes as it travels down the dorsum. The caudal fin is highly emarginate with the upper and lower caudal lobes in dark green, and the central portions entirely hyaline. The dorsal fin is dark blue with a variable amount of inter-membranous green shading, and the anal fin is completely yellow.
This species is very similar to its Pacific Ocean sister, P. heteroptera. The diagnostic differences are most apparent only in terminal males. In P. occidentalis, the vertical bars toward the caudal region do not touch the bases of the dorsal and anal fin. In P. heteroptera, the bars are fully formed, complete and always touching the dorsal and anal fin. The difference in anal fin color is also apparent between the two species, being yellow and unmarked in P. occidentalis, but edged in black in P. heteroptera. The two species have a mitochrondrial cytochrome oxidase 1 (MtCO1) gene divergence of 0.63%.
As with P. occidentalis and P. heteroptera, the newly described P. hemichrysos is the geminate twin of its Pacific Ocean counterpart, P. yamashiroi. And, like the preceding two, P. hemichrysos can only be differentiated from its sister based on coloration of the terminal males. P. hemichrysos was known from the male holotype collected in Maldives. Males of this species are purple-green over the top half of the body, demarcated from the ventral region by a stark white. The upper body is decorated in numerous short black bars, and the posterior region enveloped in a mustard saddle.
This is the defining characteristic separating both species. In the Pacific Ocean P. yamashiroi, terminal males are practically identical sans the yellow saddle. Juveniles and females are as usual, nearly indistinguishable. Both species have a MtCO1 gene divergence of 2.51%.
The last geminate pair of this genus belongs to Pseudocoris petila and P. bleekeri from the Indian and Pacific Oceans, respectively. The other three species are mostly Pacific, with P. aurantiofasciata straying weakly to the Eastern Indian Ocean. P. aequalis is restricted to the Coral Sea region and P. ocellata to Taiwan and Japan. It wouldn’t be fun if we spilled all the details on the two new species and the other seven members. Thankfully, the paper is available for free, so if you’re interested in learning more about the distribution as well as the species within Pseudocoris, do be sure to read it here.