Hymenocephalus striatissimus, : Weber, 1913

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 : 60-61

Hymenocephalus striatissimus Jordan & Gilbert, 1904

Figs. 32A–F , 37

Hymenocephalus striatissimus Jordan & Gilbert, 1904: 612 (type locality: Suruga Bay , southern Japan).

Hymenocephalus striatissimus striatissimus : Jordan & Gilbert, 1920: 527; Okamura, 1970: 48.

Material examined. 9 specimens; 5 specimens BSKU 110055 , 110102 , 110103 , 110412 , 110413 , Suruga Bay , Japan ; 3 specimens ZMUC unregistered from 13.5.1914, 115– 145 mm TL, off Cape Bonomisaki , Kyushu, southern Japan ; 1 specimen ZMUC P 375860, 125 mm TL, off Jolo Island , Philippines .

Diagnosis. Pelvic fin rays 8; pectoral fin rays 14–17; gill rakers 19–22. Barbel moderately long, 15–20% HL. Orbit 37–42% HL. Snout short, rounded, almost not protruding, 10–14% HL. Ventral striae extending to periproct. Infraorbital supporter long, 80–90% OD. Otolith compressed, OL:OH = 0.8–0.9; colliculi fused; pseudocolliculum long, TCL:PCL = 1.35–1.5.

Comparison. Hymenocephalus striatissimus differs from H. aeger in the shorter barbel (15–20% HL vs 20–25% HL), the ventral striae reaching the periproct (vs. reaching about ⅔ distance from pelvic-fin bases to periproct) and the more compressed otoliths (OL:OH = 0.8–0.9 vs 0.9–1.0). From H. torvus it differs in the higher number of pelvic fin rays (8 vs 7). From both species it appears to differ in the higher number of pectoral fin rays (14–17 vs 12–14) and also in the more blunt snout profile expressed in an unusually low snout length ratio (10–14% HL vs 15–18% HL). This latter character, however, is strongly affected by preservation and requires verification by a statistically meaningful number of well preserved specimens.

Description. Head morphology (n = 2) ( Fig. 32A–C ): Snout short, blunt, barely projecting, 10–14% HL, orbit diameter large, 37–42% HL, interorbital width 60–70% HW. Barbel moderately long, 15–20% HL, reaching slightly beyond vertical through anterior rim of orbit. Head canals well developed, infraorbital width 12–15% HL, supraorbital canal with 4 to 5 segments, width 13–15% HL, supratemporal canal rarely identifiable, above segment 3 or 4 of supraorbital canal, preopercular canal width 12–16% HL, postorbital-preopercular interspace 4–7% HL. Infranasal supporter moderately large; infraorbital supporter long, extended beyond almost entire length of orbit, 80–90% OD; preopercular supporter moderately long, 5–8% HL, with straight rear margin.

Otolith morphology (n = 10) ( Fig. 32D–F ): Otolith large; OL:OH = 0.8–0.9; OH:OT = 3.5. Dorsal rim with very large, broad, crenulated predorsal lobe, distally marked by indentation; posterior tip rounded, positioned at about level of sulcus termination; ventral rim deep, regularly curved, smooth or slightly crenulated, deepest anterior of the middle; anterior rim high, nearly vertical. Inner face slightly convex, with median sulcus. Colliculi completely fused, terminating far from anterior and posterior tips of otolith; pseudocolliculum very long. TCL:PCL = 1.35–1. 5. Dorsal depression moderately large, moderately indistinct; ventral furrow moderately distinct, close to ventral rim.

Discussion. Gilbert & Hubbs (1920) studied a large number of specimens and observed intergrades between H. striatissimus striatissimus and H. s. torvus off the northwestern coast of Luzon, Philippines. I did not study these particular specimens, but a specimen from off Jolo Island, much further south, and where they had observed intergrades between H. aeger and H. torvus , in the collection of ZMUC (P375860), which I consider as representing H. striatissimus ( Fig. 32B–C ) based on the short snout and the presence of 8 rays in the pelvic fin.

Distribution ( Fig. 37 ). Gilbert & Hubbs (1920) reported H. striatissimus from Japan, Taiwan and southwards to northern Luzon. The single specimen studied from Jolo extends the distribution further southwards.

Figures

FIGURE 32. Hymenocephalus striatissimus: A—ZMUC P15-5-1914, lateral view of head. B–C—ZMUC P375860, B—Lateral view of head, C—Dorsal view of head. D–F—Otoliths, E–F—Inner faces, D—Ventral view, D–E—BSKU 110412, F—BSKU 110102.

FIGURE 37. Geographical distribution of Hymenocephalus aeger, H. megalops, H. striatissimus, H. torvus, H. grimaldii, H. neglectissimus, H. semipellucidus, H. sp. 1 and H.