Longhead catshark

description

A. longicephalus Taiwan Holotype Other regions 1 female hermaphroditic female 13 males, 16 females, 8 unknown sex Anal base length (ceratotrichia) 15.0 14.6 13.7 – 18.4 Anal height (muscle) 3.1 2.8 2.2 – 3.9 ...... continued on the next page A. longicephalus Taiwan Holotype Other regions 1 female hermaphroditic female 13 males, 16 females, 8 unknown sex Caudal length 37.5 36.5 29.9 – 38.1 Clasper outer length 0.9 2.6 0.4 – 4.8 Counts Tooth rows: upper 42 36 35 – 45 lower 36 31 29 – 40 Vertebrae: monospondylous 33 32 29 – 33 precaudal diplospondylous 30 29 26 – 35 Spiral valves 17 15 13 – 16

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

description

Description. Proportional measurements and meristic counts are given in Table 2. Body cylindrical, slender and elongate (Figure 7). Head dorso-ventrally flattened, posterior part of body compressed laterally. Snout long, narrow; tip tapering in adults, rounded in young specimens. Pre-outer nostril length greater than interorbital width, 1.4 – 2.2 times internarial width. Pre-oral length subequal to or slightly less than pre-orbital length, 2.2 – 3.2 times internarial width, 1.3 – 2.0 times mouth width and much greater than interorbital width. Pre-orbital length 2.0 – 3.0 times interorbital length, 3.5 – 6.0 times orbit length. Internarial width slightly greater than orbit length and nostril width. Nostril expanding obliquely inward from snout edge; length 0.3 – 0.6 times pre-outer nostril length. Nostrilmouth space about half of internarial width. Mouth broadly arched, with well developed labial furrows; upper labial furrow 0.9 – 2.2 times lower one. Upper labial furrow reaching beyond midpoint between mouth corner and posterior margin of nostril. Orbit slender and narrow, with a weak subocular fold. Spiracle small placed slightly below level of horizontal axis of orbit. Five small

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

diagnosis

Diagnosis. A species of Apristurus with the following characters: upper labial furrows 0.9 – 2.2 times the lowers; first dorsal fin much smaller than the second dorsal fin, originating above posterior half of pelvic-fin base; second dorsal-fin insertion anterior to anal-fin insertion; snout narrow and long; pre-outer nostril length greater than interorbital width; abdomen short; P 1 – P 2 space shorter than anal-fin base length (ceratotrichia); pectoral-fin tip always extending beyond midpoint of P 1 – P 2 space; duodenum long, length equal to valvular intestine; intestinal spiral valves 13 – 17; monospondylous + precaudal diplospondylous vertebrae 29 – 33 + 26 – 35; clasper hook absent on edge of exorhipidion; body uniformly dark brown to light grayish; mature size at least 400 mm TL in males.

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

discussion

Remarks. Apristurus longicephalus was originally described by Nakaya (1975) based on an immature “ male ” specimen collected from Japan. This species belongs to the ‘ longicephalus group’ (sensu Nakaya & Sato, 1999) of the genus Apristurus; see remarks of A. herklotsi in further notes on the species of the ‘ longicephalus group’. Both Apristurus longicphalus and A. herklotsi appear in Taiwan, and they are clearly distinguishable by the position of first dorsal fin origin (above pelvic fin base in A. longicephalus vs. behind pelvic base in A. herklotsi), number of spiral valves (13 – 17 in A. longicephalus vs. 8 – 12 in A. herklotsi), length of duodenum (considerably long, almost equal to the valvular intestine in A. longicephalus vs. very short in A. herklotsi), among other characters. Iglésias et al. (2005 b) reported hermaphroditism in Apristurus longicephalus as the first case in the elasmobranch fishes. Nakaya (1975) described A. longicephalus based on an immature “ male ” holotype with small claspers, but Iglésias et al. (2005 b) found the holotype to have been an adolescent hermaphroditic “ female ” with a developing ovary. They also pointed out that the ratios of hermaphrodi

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters