Hymenocephalus longibarbis ( Günther, 1887 )

Schwarzhans, Werner, 2014, Head and otolith morphology of the genera Hymenocephalus, Hymenogadus and Spicomacrurus (Macrouridae), with the description of three new species, Zootaxa 3888 (1), pp. 1-73 : 27-29

Hymenocephalus longibarbis ( Günther, 1887)

Figs. 8A–L , 12

Macrurus longibarbis Günther 1887: 139 (type locality: Fiji, 19°09’S, 179°41’E).

Hymenocephalus longibarbis: Iwamoto & Merrett, 1997: 520 ; Iwamoto & Williams, 1999: 177; Merrett & Iwamoto 2000: 757. Hymenocephalus longiceps Smith & Radcliffe, 1912: 111 (type locality: Philippines, off Luzon, 13°10’N, 123°59’E). Hymenocephalus longiceps: Gilbert & Hubbs, 1916: 145 ; Gilbert & Hubbs, 1920: 520; Okamura, 1970: 45.

Hymenocephalus striatissimus: Weber, 1913: 168 .

Material examined. 27 specimens; 1 specimen BMNH 1887.12 .7.94 (holotype), 140 mm TL, 19°09’S, 179°41’E, 576 m , Challenger; 1 specimen AMS I.23423-018, 160 mm TL, 18°01’S, 118°23’E; 1 specimen AMS I.32433- 008, 255 mm TL, 10°29’S, 144°01’E; 3 specimens AMS I.40292-002, 166, 180, 216+ mm TL, 36°29’S, 150°21’E; 1 specimen (otolith only) BSKU 106798, 210 mm TL, Kagoshima , off Kyushu Island ; 1 specimen (otolith only) BSKU 106800, 193 mm TL, Kagoshima , off Kyushu Island ; 1 specimen BSKU 110100, 173 mm TL, Suruga Bay ; 1 specimen BSKU 110104 , 98 mm TL, Suruga Bay ; 1 specimen LACM 42620-1 , 144 + mm TL, E of Sydney ; 3 specimens (2 otoliths only) MNHN 2006-0020 , 176 mm TL, 08°16’S, 160°04’E, 464–523 m ; 1 specimen MNHN 2006-0159 , 182 + mm TL, 07°44’S, 156°29’E, 518–527 m ; 1 specimen (otolith only) MNHN 2008-2433 , 15°07’S, 167°03’E, 420–670 m ; NSMT P. 94559, 185 mm TL, KH-02-4 station S1-C; 1 specimen (otolith only) USNM 149296 , 16°38’N, 119°57’E ; 1 specimen USNM 149298 , 125 + mm TL, 05°52’N, 120°31’E ; 1 specimen USNM 149299, 188 mm TL, 00°15’N, 127°24’E ; 2 specimens WAM P.28058-014, 200 and 211 mm TL, 18°05’S, 118°10’E ; 1 specimen WAM P.28071-020, 159 mm TL, 18°08’S, 118°31’E ; 4 specimens ZMUC reg. 1.2.1928, 95, 99, 125 and 127 mm TL, off Jolo , Philippines .

Diagnosis. Pelvic fin rays 8; pectoral fin rays 13–17; snout barely projecting; head bones rather firm; barbel very long, 50–60% HL, reaching vertical through posterior edge of orbit; orbit diameter 30–33% HL; interorbital width 45–48% HW; gill rakers 16–20; ventral striae reaching close to periproct; OL:OH = 1.1–1.3; TCL:PCL = 1.8–2.1.

Comparison. Hymenocephalus longibarbis resembles H. longipes , differing primarily in the very long barbel (vs no barbel) and the absence of black pigmentation on the pelvic fin (vs black tip).

Description. Head morphology (n = 3) ( Fig. 8A–C ): Head with rounded, soft-tipped snout, barely projecting. Snout length 15–20% HL, orbit diameter 30–33% HL, interorbital width 45–50% HW. Barbel 50–60% HL, reaching vertical through posterior edge of orbit. Head canals well developed, infraorbital width 12–15% HL, supraorbital canal with 6 segments, width 7–10% HL, supratemporal canal narrow, above segment 4 of supraorbital canal (information provided by N. Nakayama, BSKU), preopercular canal width 10–15% HL, postorbitalpreopercular interspace 9–11% HL. Infranasal supporter small; infraorbital supporter moderately widened throughout length below orbit, expanded beyond rear of orbit, 90–110% OD; preopercular supporter broad, with straight rear margin, short (3–5% HL).

Otolith morphology (n = 20) ( Fig. 8D–L ): Otolith moderately high bodied; OL:OH = 1.1–1.3; OL:OT about 3. Predorsal lobe large, mostly triangular in shape, often crenulated marginally, gently inclining towards rear part of otolith. Anterior rim irregular, broadly rounded; posterior tip moderately pointed, sometimes with incision at cauda. Ventral rim deep, smooth and regularly curved, deepest anterior of middle. Inner face slightly convex along horizontal axis, with slightly supramedian sulcus. Ostial and caudal colliculi moderately large, closely separated at collum, terminating at some distance from anterior and posterior tips of otolith; pseudocolliculum moderately enlarged. CCL:OCL = 0.7–1.3; TCL:PCL = 1.8–2.1. Dorsal depression moderately wide; ventral furrow thin, close to ventral rim.

Discussion. When Smith and Radcliffe (1912) described H. longiceps , they stated that “the species resembles H. longibarbis Günther , and may prove to be identical with it”. Okamura (1970) noted that the two species could be differentiated by H. longiceps having more pectoral fin rays and a shorter barbel. Iwamoto & Merrett (1997) discussed the relationship of the two nominal species and concluded that the difference of pectoral fin rays given as 11 for the holotype of H. longibarbis (vs 14–17 for H. longiceps ) is based on an erroneous measure by Günther and that differences in barbel lengths are not verified. Both observations are clearly supported by my review of the holotype of H. longibarbis as well as the many other specimens of both nominal species reviewed from a large variety of locations. Iwamoto & Merrett nevertheless retained both species based on differences in snout length (apparently measured slightly differently from my method, which arrives at slightly lower values) and small differences in interorbital and suborbital width. I failed to verify these differences, and consider H. longiceps as a junior synonym of H. longibarbis .

Notwithstanding the above, one can observe certain statistical variations in the otolith shapes which appear to relate to geographical differences. Otoliths of specimens from Japan ( Fig. 6D–F ) exhibit a more intense marginal crenulation and a more regular triangular shape of the dorsal rim than the ones from the Philippines to NE Australia ( Fig. 6G–J ). Some specimens from off Australia, particularly off Western Australia ( Fig. 6K–L ), show a relatively low predorsal lobe. However, I was unable to relate these subtle differences in otolith morphology to any other morphological differences of the fishes and therefore regard them as representing intraspecific variations.

Distribution ( Fig. 12 ). Following the synonymization of H. longiceps , H. longibarbis now maintains a rather wide geographical distribution in the West Pacific from southern Japan in the north to the Philippines and Indonesia and further south to New Caledonia and northern Australia from Queensland to Western Australia.

Figures

FIGURE 6. Heads and otoliths of the species of Hymenogadus: A–I—Hymenogadus gracilis, A–D—ZMH 111113, A—Dorsal view of head, B—Ventral view of head and trunk, C–D—Lateral views of head, E—Inner face of otolith, coll. Schwarzhans (leg. IRSNB), F–H—USNM 131873, F—Anterior view of otolith, G—Inner face of otolith, H—Ventral view of otolith, I—ZMH 107658, inner face of otolith. J–L—Hymenogadus tenuis, holotype, J—Lateral view of head, K—Dorsal view of head, L—Radiograph of head depicting otolith.

FIGURE 8. Hymenocephalus longibarbis: A–B—USNM 149298, A—Lateral view of head, B—Dorsal view of head. C—Holotype, BMNH 1887.12.7,94, lateral view of head. D–L—Otoliths, inner faces, D—BSKU 106798, E—BSKU 110100, F—BSKU 110104, G—USNM 149296, H—LACM 42620-1, I—MNHN 2006-0159, J,L—WAM P.28058-014, K—AMS I.32433-008.

FIGURE 12. Geographical distribution of Hymenocephalus longibarbis, H. longipes and H. iwamotoi.