Epigonus idai, Okamoto & Gon, 2018

Okamoto, Makoto & Gon, Ofer, 2018, A review of the deepwater cardinalfish genus Epigonus (Perciformes: Epigonidae) of the Western Indian Ocean, with description of two new species, Zootaxa 4382 (2), pp. 261-291 : 274-276

Epigonus idai n. sp.

(New English name: Ida’s Deepwater Cardinalfish) ( Figs. 3 , 6B , 7B , 11 ; Tables 1–3)

Holotype. SAIAB 82171 , 136.8 mm SL, male, 20°35.6 S, 35°58.3 E, off Mozambique, western South Indian Ocean, 709–721 m depth, 19 October 2007, bottom trawl, collected by P. C. Heemstra and E. Heemstra.

Paratype. SAIAB 204434 (formerly SAIAB 82171), 132.3 mm SL, male, same data as holotype.

Diagnosis. A species of Epigonus with the following combination of characters: dorsal-fin rays VII-I, 10; pectoral-fin rays 18–19; total gill rakers 28–29; vertebrae 10 + 15; pyloric caeca 10–12; pored lateral-line scales 48–49 + 3; scales strongly ctenoid; scales below lateral line 10; pungent opercular spine present; maxillary mustache-like process absent; ribs on last abdominal vertebra present; and 4–5 tiny projections present on symphysis of lower jaw.

Description. Counts and measurements of holotype and paratype are shown in Tables 1–3. Body elongate, laterally compressed, deepest at pectoral-fin base; nape not humped. Head large, broad. Maxillary mustache-like processes absent. Snout short and round, length slightly longer than interorbital width; nostrils closely set at level of upper edge of pupil, anterior nostril without membranous tube, posterior nostril elliptical without dermal flap. Eye large, round, orbital diameter greater than postorbital length; bony rim of orbit slightly raised above dorsal profile; interorbital region broad, concave at center of posterior half. Mouth large, terminal; gape oblique; posterior margin of maxilla not extending to below center of pupil; lower jaw not projecting when mouth closed; tiny 4–5 projections present on symphysis of lower jaw ( Fig. 6B ). Teeth minute, arranged in 2–3 rows on anterior half of premaxilla and dentary, a single row on posterior half of both bones. Small number of minute teeth present on vomer and palatine. Basihyal toothless. Opercular spine strong, pungent, forming ridge; posterior corner of preopercle weakly serrated. Origin of first dorsal fin above anterior part of pectoral fin; first dorsal-fin spine short; third dorsal-fin spine longest; no isolated dorsal-fin spine between first and second dorsal fins. Spine of second dorsal fin long, slightly thicker than those of first dorsal fin. Origin of anal fin below posterior part of second dorsal-fin base; first anal-fin spine minute; second anal-fin spine long, but its length slightly shorter than second dorsal-fin spine. Proximal radial of first anal-fin pterygiophore slender. Pectoral and pelvic fins short, posterior tip of both fins not reaching vertical drawn from anus; upper margin of pectoral-fin base lower than level of horizontal line through center of pupil. Caudal fin deeply forked. Anus located slightly anterior to vertical drawn through origin of second dorsal fin. Ribs present on last abdominal vertebra. Supraneural bones three (0+0/0+2/1+1/1/). Scales large, deciduous, strongly ctenoid ( Fig. 7B ), covering whole body except for area anterior to rim of orbit and surfaces of jaws; small scales also present on bases of second dorsal, anal, and caudal fins; series of pored lateralline scales complete, 3 pored scales on caudal fin. Ventral luminous organ absent.

Color when fresh (based on Fig. 11A ). Body uniformly tan; pectoral, second dorsal, anal, and caudal fins light brown; first dorsal and pelvic fins black. Head light brown and opercle with bluish reflection.

Color in alcohol. Body, pectoral and caudal fins, head (except gill cover which is dark-brown), and mouth cavity with tongue light brown. First and second dorsal, pelvic, and anal fins dark brown.

Distribution. The holotype and paratype were collected off Mozambique, western South Indian Ocean ( Fig. 3 ), at a depth of 709– 721 m.

Etymology. The specific name is in honor of Dr Hitoshi Ida (Professor Emeritus, Kitasato University, School of Marine Biosciences) for his contribution to Epigonus (see Ida et al., 2007) and other percoid studies in the Indo- Pacific region.

Comparisons and Remarks. Epigonus idai belongs to the E. constanciae group by having a pungent opercular spine (Okamoto 2012). Epigonus idai is unique in this species group in having 4–5 tiny projections on the symphysis of lower jaw ( Fig. 6B ). In addition to the diagnostic characters, E. idai differs from 20 species of the group in having 10 + 15 vertebrae (vs. 11 + 14 in E. chilensis , E. crassicaudus , E. heracleus , E. lenimen , E. machaera , E. robustus ), 10 soft rays on the second dorsal fin (vs. 9 soft rays in E. affinis , E. elegans , and E. waltersensis ), 28–29 gill rakers (vs. 20–26 in E. atherinoides , E. ctenolepis , E. draco , E. megalops , E. okamotoi , E. occidentalis ), a pair of ribs on the last abdominal vertebra (vs. absent in E. marimonticolus and E. thai ), and lacking a pair of maxillary mustache-like processes (vs. a sharp-pointed maxillary mustache-like processes present in E. constanciae , E. mayeri , and E. pectinifer ). The diagnostic characters separating the two new species in the present study are described in the Comparison of E. bispinosus above.

Figures

FIGURE 3. Distribution of seven species of the Epigonus constanciae group inthe Western Indian Ocean.

FIGURE 7. Pored lateral-line scales. A: Epigonus bispinosus n. sp., SAIAB 189476, holotype, 165.5 mm SL; B: E. idai, n. sp., SAIAB 204434, paratype, 132.3 mm SL.

FIGURE 11. Epigonus idai n. sp., SAIAB 82171, holotype, 136.8 mm SL; A: fresh specimen; B: preserved specimen; C: radiograph.

FIGURE6. Ventral viewof symphysis of lowerjaw.A:Epigonus bispinosusn. sp., SAIAB35606, 1of 5 paratypes,141.7 mm SL; B: Epigonus idai n. sp., SAIAB 204434, paratype, 132.3 mm SL.