Hymenocephalus italicus Giglioli, 1884

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 : 55-58

Hymenocephalus italicus Giglioli, 1884

Figs. 28A–P , 29

Hymenocephalus italicus Giglioli, 1884: 228 (type locality: off Genoa , Italy).

Hymenocephalus italicus: Vaillant, 1888: 211 ; Marshall & Iwamoto, 1973: 605; Iwamoto in Cohen et al., 1990: 230. Bathygadus cavernosus Goode & Bean 1885: 598 .

Hymenocephalus cavernosus: Goode & Bean, 1896: 408 .

Macrurus (Mystaconurus) cavernosus: Alcock, 1899: 117 (Gulf of Mexico only).

Material examined. 63 specimens; 12 specimens BMNH 1939.5.24.705–716, 04°58’N, 73°16’E ; 4 specimens IORAS 00224 , 88–135 mm TL, 25°28’S, 35°14’E ; 1 specimen IORAS 00225 , 171 mm TL, 09°28’S, 60°08’E ; 8 specimens IORAS 00226 , 104–160 mm TL, 08°47’S, 59°55’E ; 2 specimens MCZ 43020, 125 + –127+ mm TL, 07°40’N, 54°47’W, 548 m ; 7 specimens MCZ 43049, 29°08’N, 88°13’W, 457 m ; 1 specimen (otolith only) MCZ 51404, 23°22’N, 79°56’W, 521–548 m ; 3 specimens (otoliths only) MVZ 52949, 21°21’N, 17°37’W, 400 m ; 1 specimen MCZ 57926, 11°36’N, 62°46’W, 530 m ; 2 specimens USNM 109502 , 123 and 152 mm TL, Maldives, Kardiva channel, 5°N, 73°E , John Murray Expedition; 1 specimen ZMB 17646, 165 mm TL, 00°27’N, 42°47’E ; 1 specimen ZMB 22336, 137 + mm TL, 01°40’N, 41°47’E ; 1 specimen ZMB 22337, 144 + mm TL, 00°27’N, 42°47’E ; 1 specimen ZMB 34033, 166 mm TL, off Mauritania ; 1 specimen ZMB 34055, 158 mm TL, off Mauritania ; 3 specimens ZMB 34063, 125– 146 mm TL, off Mauritania ; 3 specimens ZMUC 23.8.1890, journal 52.53.57, 95– 105 mm TL, off Morocco ; 2 specimens ZMUC 1.11.1892, 81– 114 mm TL, off Messina , Italy ; 8 specimens ZMUC 373411–373418 , 74 + – 178 mm TL, 29°55’S, 31°20’E ; 1 specimen (otolith only) leg. John Fitch, Mediterranean (no further data).

Diagnosis. Pelvic fin rays 11, rarely 10 or 12; pectoral 12–14; gill rakers 20–25. Barbel short 7–12% HL, not or just reaching vertical through anterior rim of orbit. Orbit 34–38% HL. Snout pointed, protruding, 18–20% HL. Ventral striae extending to about ½ to ⅔ the distance from pelvic fin bases to periproct ( Fig. 28G ). Otolith compressed, OL:OH = 0.8–0.95; colliculi fused; pseudocolliculum long, TCL:PCL = 1.5–1.7.

Comparison. Hymenocephalus italicus resembles H. heterolepis and H. punt but differs from both in having a larger orbit (34–38% HL vs 28–32% HL) and a compressed otolith with fused colliculi (vs. separated colliculi). The latter is also the best character to distinguish it from the otherwise closely similar H. antraeus , which further differs in having a shorter barbel (3–4% HL vs. 7–12% HL) and the more rounded and less protruding snout.

Description. Head morphology (n = 4) ( Fig. 28A–F ): Snout moderately long, pointed, projecting, 18–20% HL, orbit diameter large, 34–38% HL, interorbital width 55–70% HW. Barbel short, 7–12% HL, mostly reaching vertical through anterior rim of orbit. Head canals well developed, infraorbital width 9–14% HL, supraorbital canal with 5–6 segments, width 12–15% HL, supratemporal canal moderately wide, above segment 4 of supraorbital canal, preopercular canal width 12–16% HL, postorbital-preopercular interspace 5–7% HL. Infranasal supporter moderately large; infraorbital supporter short, expanding only beyond rear part of orbit, 30–50% OD; preopercular supporter moderately long, 4–7% HL, with straight rear margin.

Otolith morphology (n = 9) ( Fig. 28I–P ): Otolith large; OL:OH = 0.8–0.95; OH:OT = 3.5. Dorsal rim with very large and broad, often crenulated predorsal lobe, distally inclining to posterior tip with small incision; posterior tip at about level of sulcus termination; ventral rim deep, regularly curved, mostly smooth, deepest anterior of the middle; anterior rim high, subvertical to 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 = 1.5–1.7. Dorsal depression moderately large, indistinct; ventral furrow moderately distinct, close to ventral rim.

Discussion. Hymenocephalus italicus is one of the more widespread species of the genus and specimens were examined from a variety of geographic origins. Specimens from the western Atlantic ( Fig 28A, D ) and Indian Ocean ( Fig. 28C, F ) generally seem to have slightly longer barbels than those from the eastern Atlantic ( Fig. 28B, E ). Otoliths from specimens from the western Atlantic ( Fig. 28I, N ) are generally more compressed and have a smoother outline than those from specimens from the eastern Atlantic ( Fig. 28J, O ) or the Indian Ocean ( Fig. 28K–M, P ). However, none of these subtle differences appear to be stable enough to warrant distinction at the species or even the subspecies level. Larger statistical series would have to be analyzed or DNA-methods applied for confirmation of any distinction between them.

Distribution ( Fig. 29 ). Hymenocephalus italicus is common in the tropical western Atlantic, in the eastern Atlantic from Portugal to Angola, the Mediterranean and the western Indian Ocean so far recorded from off southern Somalia to Zanzibar, off Mozambique to Durban, along the Mascarene Ridge and off Maldives. Reports from the eastern Indian Ocean (Bay of Bengal and Andaman Sea) represent H. heterolepis and records from the Gulf of Aden represent H. punt .

Figures

FIGURE 28. Hymenocephalus italicus: A, D—MCZ 43049, A—Lateral view of head, D—Dorsal view of head. B, E—ZMUC P373417, B—Lateral view of head, E—Dorsal view of head. C, F—IORAS 00225, C—Lateral view of head, F—Dorsal view of head. G–H—USNM 109502, G—Ventral view of head and trunk, H—detail view of posterior lens of ventral luminescent organ. I–P—Otoliths, I–K, N–P—Inner faces, L—Ventral view, M—Anterior view, I—MCZ 43020, J—MCZ 52949, K–M—IORAS 00226, N—MCZ 51404, O—ZMUC P.23-8-1890, P—USNM 109502.

FIGURE 29. Geographical distribution of Hymenocephalus italicus.