Apristurus gibbosus Meng, Chu

Apristurus gibbosus Meng, Chu View in CoL & Li, 1985

English name: Humpback catshark Taiwanese name: Tuo-bei-bi-sa

Japanese name: Nankai herazame ( Figure 13–21 View FIGURE 13 View FIGURE 14 View FIGURE 15 View FIGURE 16 View FIGURE 17 View FIGURE 18 View FIGURE 19 View FIGURE 20 View FIGURE 21 , Table 3 View TABLE 3 )

Apristurus gibbosus Meng, Chu & Li, 1985: 43, fig. 1 (original description, type locality: South China Sea); Nakaya & Sato, 1999: 316 (taxonomic comments, South China Sea); Nakaya & Séret, 1999: 307 (taxonomic comments, South China Sea), Compagno, 1999: 478 (taxonomic comments, South China Sea); Compagno et al., 2005: 189–190, pl. 33 (description, China); Ebert et al., 2013: 288, pl. 39 (description).

Material examined. Taiwan: NMMBP 17562, mature female, 491 mm TL, Da-xi. Other regions (type specimens): SCSFRI D-01121 (holotype of A. gibbosus ), female, 425 mm TL, off the estuary of Pearl River, South China Sea, China, 913 m depth. SFC D-01133 (paratype of A. gibbosus ), female, 396 mm TL, SFC D-0084 (paratype of A. gibbosus ), female, 369 mm TL, off the estuary of Pearl River, South China Sea, China, 913 m depth. Other regions (non types): BSKU 23016, female, 281 mm TL, BSKU 23017, female, 358.1 mm TL, BSKU 23060, female, 306.5 mm TL, BSKU 26357, male 337 mm TL, BSKU 26454, female, 333 mm TL, BSKU 26511, female, 325 mm TL, BSKU 28098, female, 475.8 mm TL, BSKU 28099, male, 547.5 mm TL; BSKU 28100, female, 392 mm TL, BSKU 28101, male, 403 mm TL, BSKU 28165, female, 444 mm TL, BSKU 33526, male, 231 mm TL, Okinawa Trough, East China Sea, Japan; HUMZ 145164, male, 476 mm TL, Okinawa Trough, East China Sea, Japan (28°00.03’N, 128°21.90’E- 27°59.88’N, 128°24.56’E); HUMZ 145166, male, 309 mm TL, HUMZ 145171, male, 542 mm TL, Okinawa Trough, East China Sea, Japan (28°33.29’N, 127°09.96’E- 28°35.30’N, 127°11.22’E); SFU D-0094, male, 494 mm TL, SFU D-0300, male, 387 mm TL, SFU D-0339, female, 426 mm TL, SFU D-0700, female, 313 mm TL, SFU D-2268, male, 382 mm TL, SFU E-0174, female, 404 mm TL, SFU e18-00097, male, 465 mm TL, East China Sea, China.

Diagnosis. A species of Apristurus with the following characters: upper labial furrows longer than the lowers; first dorsal fin slightly smaller than second dorsal fin, originating above middle of pelvic-fin base; second dorsal-fin insertion anterior to anal-fin insertion; snout relatively short and broad; tip bell-shaped; abdomen long; P1–P2 space longer than anal-fin base length (ceratotrichia); pectoral-fin tip always anterior to midpoint of P1–P2 space; intestinal spiral valves 16–21; monospondylous + precaudal diplospondylous vertebrae 37–43 + 25–31; small dermal denticles giving a velvety texture to body surface; clasper hook absent on edge of exorhipidion, posterior margin of exorhipidion lacking free posterior end; body uniformly dark to blackish brown; maturingsize at least 400 mm TL in males and 450 mm TL in females.

Description. Proportional measurements and meristic counts are given in Table 3 View TABLE 3 . Body cylindrical, moderately slender and elongate ( Figure 13 View FIGURE 13 ). Head dorso-ventrally flattened, posterior part of body compressed laterally. Snout relatively short andbroad; its tip bell-shaped. Pre-outer nostril length 0.9–1.4 times internarial width. Pre-oral length 0.8–1.0 times pre-orbital length, 1.9–2.7 times internarial width, 0.8–1.1 times mouth width and 1.0–1.3 times interorbital width. Pre-orbital length1.2–1.6 times interorbital length, 2.8–4.8 times orbit length. Internarial width slightly greater than orbit length and shorter than nostril width. Nostril expanding obliquely inward from snout edge; length about 2/3 of pre-inner nostril length. Nostril-mouth space about half of internarial width. Mouth broadly arched, with well developed labial furrows; upper labial furrow1.1–1.6 times longer than lower one. Upper labial furrow reaching beyond midpoint between mouth corner and posterior margin of nostril. Orbit relatively large and slender, with a weak subocular fold. Spiracle small placed slightly below level of horizontal axis of orbit. Five small gill slits present; fourth gill slit above pectoral-fin origin; fifth gill slit smallest, above pectoral fin base. Gill septa with a projection, densely covered with dermal denticles. Abdomen long; P1–P2 space longer than analfin base length (ceratotrichia); pectoral-fin tip always anterior to midpoint of P1–P2 space. Pectoral fin small in size, rather narrow, sub-trianglular; outer margin not parallel to inner margin. Pelvic fin relatively low and long; its length subequal to pre-orbital length. Dorsal fins similar in shape. First dorsal fin slightly smaller than second; origin above middle of pelvic-fin base; insertion anterior to anal-fin origin. Second dorsal-fin origin above middle of anal-fin base; insertion anterior to anal-fin insertion. Anal fin relatively high, triangular, with a base much shorter than P1–P2 space; apex clearly posterior to first dorsal-fin insertion; posterior margin straight; anal and caudal fins separated only by a notch. Caudal fin slightly slender; ventral lobe not produced: apex of ventral lobe rounded; subterminal notch distinct; length of terminal lobe twice caudal terminal lobe height. Caudal peduncle height 1.0–1.4 times pre-outer nostril length. Duodenum very short

Intestinal spiral valves 16–21. Monospondylous vertebrae 37–43; precaudal diplospondylous vertebrae 25–31.

Teeth numerous and small, 63–96 rows on upper jaw, 64–98 rows on lower jaw with one long central cusp and one to two short lateral cusps.

Egg capsule ( Figure 14 View FIGURE 14 ) taken from 444 mm TL specimen (BSKU 28165) 48.5 mm long and 18.7 mm wide in a cylindrical shape, with fibrous thread on anterior ends and coiled tendrils on posterior ends; anterior margin of the capsule rounded with fibrous thread at each corner; lateral edges flanged; posterior tip separated with tendrils. Surface of egg capsule with ridges. Color light brownish.

Dermal denticles from dorso-lateral side of body small ( Figure 15 View FIGURE 15 ), overlapping each other, tricuspid, with a long ridged central cusp and shorter lateral cusps; outer surface of denticles completely structured by reticulations. No modified dermal denticles on the dorsal margin of the caudal fin. Dermal denticles densely present around the gill slits and on gill septa.

Clasper stout at base, tapering posteriorly ( Figure 16 View FIGURE 16 ). Ventral and outer side of surface covered with dermal denticles. Dorsal side of clasper naked and ventral and lateral sides covered with clasper denticles; clasper hooks absent on edge of exorhipidion; pseudosiphon slit-like in shape; cover rhipidion vestigial; pseudopera large and deep; exorhipidion simple in shape, without free posterior end.

Color. Upper and lower surfaces of body and fins uniformly dark to blackish brown with light brownish naked areas along the fin margins. Tongue and palate blackish brown.

Size. Maximum size 547.5 mm TL in male ( Figure 17 View FIGURE 17 ). Males less than 403 mm TL in maturity stage 1 (immature) with short claspers, less than 3.3% TL. Males more than 465 mm TL in maturity stage 3 (adult) with long, well developed and hardened claspers. Females less than 444 mm TL in maturity stage 1. Females more than 450 mm TL in maturity stage 3.

Distribution. South China Sea and northward to East China Sea (Okinawa Trough) ( Figure 18 View FIGURE 18 ).

Remarks. Apristurus gibbosus was originally described by Meng et al. (1985) based on three specimens collected from the South China Sea. This species belongs to the ‘brunneus group’ (sensu Nakaya & Sato, 1999) of the genus Apristurus , characterized by having a considerably longer labial furrow on the upper jaw than on the lower jaw, and more numbers of spiral valves in the intestine.

Apristurus gibbosus is characterized by a long P1–P2 space, which is greater than the anal-fin base length (ceratotrichia) and pectoral-fin tip that does not reach the midpoint of the P1–P2 space. As such, A. gibbosus is clearly distinguishable from other species of Taiwanese Apristurus by these characters. Although Meng et al. (1985) described “dorsal outline behind eye highly convexed” as one of the diagnostic characters of this species, this is apparently based on a transformation during fixation (personal observation of the type specimens by Nakaya).

A. gibbosus

Taiwan Holotype Paratypes East China Sea D2 free lobe length 4.2 ― ― ―

...... continued on the next page TABLE 3 View TABLE 3 . (Continued) A. gibbosus

Taiwan Holotype Paratypes East China Sea Apristurus gibbosus is similar to Japanese A. japonicus in having a long P1–P2 space, but A. gibbosus is distinct from A. japonicus in having a shorter snout ( Figure 19 View FIGURE 19 ) and a narrower internarial width ( Figure 20 View FIGURE 20 ). Apristurus gibbosus is apparently a smaller species, which matures at lengths of 40–45 cm TL in both sexes, and attains 57 cm TL, while A. japonicus matures at lengths of 55–60 cm TL, and attains more than 70 cm TL ( Figure 21 View FIGURE 21 ).

This is the first report of Apristurus gibbosus from Taiwan.