Kopua japonica, Moore, Glenn I., Hutchins, Barry & Okamoto, Makoto, 2012

Moore, Glenn I., Hutchins, Barry & Okamoto, Makoto, 2012, A new species of the deepwater clingfish genus Kopua (Gobiesociformes: Gobiesocidae) from the East China Sea — an example of antitropicality?, Zootaxa 3380, pp. 34-38 : 35-37

Kopua japonica sp. nov.

Figures 1–3

Standard English name: Japanese Deepwater Clingfish Standard Japanese name: Yozakura-ubauo

Holotype NSMT-P 106831, 29.6 mm SL, East China Sea, Japan-Korea Joint Development Zone (EEZ) (30o06’N, 127 o39’E), collected by bottom trawl at 225–228 m, M. Okamoto, 7 June 2010.

Diagnosis. This species is placed in the genus Kopua on the basis of its large eyes, separated by a very narrow interorbital, and the distinctive fringed posterior ventral sucking disc. It is distinguished from both Kopua nuimata and Kopua kuiteri by possessing 5 anal fin rays (versus 8 or 9 and 7 in the latter species, respectively) and 3 sensory head pores (versus 7 and 2 in the latter species, respectively). It is further separated from K. nuimata by a lower dorsal fin ray count (6 versus 10 or 11).

Description. All measurements are based on the unique holotype (with proportional dimensions in parentheses).

Dorsal fin rays 6; anal fin rays 5; pectoral fin rays 23; pelvic fin elements I (short, embedded), 4; caudal fin rays 15 (segmented); all rays in all fins are simple; vertebrae, including hypural plate 33.

Body moderately robust, sub-cylindrical anteriorly and laterally compressed posteriorly, 29.6 mm SL, 36.5 mm TL, maximum depth 5.4 mm (18.2 %SL); width at pectoral fin base 6.5 mm (22.0 %SL); head moderately wide posteriorly and somewhat depressed, head length 10.2 mm (34.5 %SL) and head width 6.7 mm (65.7 %HL); snout triangular, length 2.4 mm (23.5 %HL); caudal peduncle stout, length 2.9 mm, depth 2.8 mm; nostrils moderate in size, tubular (anterior longest), without flaps; posterior nostril just anterior to eye; eye large, diameter 3.2 mm (31.4 %HL); bony interorbital very narrow, width 0.7 mm (6.9 %HL).

Skin is smooth and scaleless; three pairs of moderate-sized cephalic sensory pores, one nasal, one lacrymal and one postocular ( Fig. 1), each with a short tubular opening; a few minute papillae distributed on head, especially behind corner of mouth. Ventral disc double, moderately large; striated posterior fringe long and distinctly squared ( Fig. 2); total disc length 7.3 mm (24.7 %SL). Papillae are missing from holotype, presumed lost during collection; numerous sub-dermal blotches (observed following staining) are thought to reflect the position of papillae on the posterior disc (these blotches were used to illustrate Fig. 2); no such blotches were seen on the anterior disc or pelvic fins.

POP

LP

PN

AN

NP

Mouth slightly subterminal; large fleshy lips; teeth moderate sized, conical and rounded; upper jaw with single row laterally and two rows anteriorly; lower jaw with several longer and slightly recurved teeth laterally; lower jaw also with tooth patches anteriorly (around symphysis) and front row projecting slightly forward; palatine and vomerine tooth patches absent; gill opening wide; membranes joined across isthmus, but not attached to it; gill filaments fleshy; gill rakers short (unable to be counted).

Bases of dorsal and anal fins short, 3.8 mm and 2.7 mm, respectively; snout to origin of dorsal fin 23.2 mm (78.4 %SL), which is slightly anterior to the origin of anal fin; axial dermal flap very small; urogenital opening midway between origin of anal fin and rear margin of ventral disc; no genital papillae evident on holotype.

Colour of holotype in alcohol is overall pale yellowish brown with blackish eyes. Colour when fresh (based on photographs of freshly collected holotype; Fig. 3 ): base colour pale cream-white, with numerous bright reddishorange bars on sides of body that merge dorsally to form distinctive arches. Dorsum with numerous yellowish bands on pink-orange background. Head and operculum orange. Eye gold, tending blackish dorsally, with pale ring around a black pupil. All fins are translucent orange, except pelvic fins, which are hyaline white.

Distribution. Kopua japonica is currently known only from the type locality in the East China Sea.

Etymology. The specific name reflects the type locality.

Comparisons. Kopua japonica shares many features with its congeners. In particular, all have large eyes, separated by a very narrow interorbital and similar-shaped ventral sucking discs. The arrangement of both the teeth and nostrils are comparable in all species and they all have a similar body shape, with equivalent proportions. The live colour of K. japonica is similar to that of K. kuiteri , however the distinctive lateral arches on the former species has not been seen on the latter (see Australian Museum 2011); the colouration of K. nuimata is unknown. Furthermore, all species are known only from deep water; at least 90 m, and generally deeper. However, K. japonica has only 5 anal fin rays (versus 7 in K. kuiteri and 8 or 9 in K. nuimata ), and shares a dorsal fin ray count only with K. kuiteri (6 versus 10 or 11 in K. nuimata ). The three species also differ in the number of sensory head pores: K. kuiteri only has an anterior nasal pore and a postocular pore, K. japonica has those pores and a lacrymal pore, and K. nuimata has two nasal pores, two lacrymal pores, a postocular pore and a preopercular pore on each side of the head.

Remarks on the distribution of Kopua . Kopua japonica is the first representative of the genus reported from outside temperate Australian-New Zealand waters and is an important extension of the known distribution of the genus Kopua into the Northern Hemisphere. Such a temperate Japan-Australia disjunct distribution pattern is known among other genera and species (e.g., Burridge & White 2000; Mabuchi et al. 2004; Okamoto et al. 2011), and Kopua may represent another generic example. This might also be the first for the Gobiesocidae , since other genera of clingfishes with representatives in each hemisphere (e.g., Gobiesox and Lepadichthys ) are not antitropical because they also have congeners with an intermediate (equatorial) distribution (see Briggs 1955).

There are three main possible biogeographic explanations for the observation of antitropicality in Kopua . Firstly, divergence between species might be the result of isolation by dispersal across the tropics. Burridge (2002) argued that dispersal was the most common explanation for antitropicality in a range of Pacific fishes. This was thought most likely to have occurred either during recent glaciations when tropical sea temperatures were lower, or by moving through deeper water where temperatures remain cool (e.g., Burridge 2002; Hubbs 1952). Irrespective of the mode, equatorial transgressions are especially likely in taxa with high dispersal potential. However the capacity for dispersal in gobiesocids is probably quite low, because all representatives of the family for which data are known have demersal eggs and a short pelagic larval stage ( Beldade et al. 2007; Leis & Rennis 1983; Macpherson & Raventós 2006), and it would be unlikely for larvae to be transported across the equator. Since they are apparently restricted to deep water, dispersal across the equator could also be considered unlikely for adult Kopua . The second possible biogeographic explanation for antitropicality is vicariant isolation. In this case, such an explanation might involve the existence of an ancestral Kopua , which once occupied a widespread area and later became extinct in the tropics, leaving isolated northern and southern populations to evolve into separate species (e.g., Briggs 1987; Crame 1993). Finally, it is possible that other species of Kopua exist in tropical regions and the genus has a more or less continuous distribution as observed for other gobiesocids. This cannot be disregarded, given that the species of Kopua inhabit deep water and are very small and probably difficult to collect as suggested by the paucity of specimens of all species. However, it is certainly noteworthy that examples of antitropicality are scarce from deep water taxa ( Burridge 2002; Hubbs 1952; Randall 1981).

Figures

FIGURE 3. Lateral and dorsal photographs of live colouration of Kopua japonica sp. nov., holotype, NSMT-P 106831, 29.6 mm SL (photo: M. Okamoto).