Apristurus longicephalus Nakaya, 1975

Nakaya, Kazuhiro & Kawauchi, Junro, 2013, A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters, Zootaxa 3752 (1), pp. 130-171 : 138-143

Apristurus longicephalus Nakaya, 1975

English name: Longhead catshark Taiwanese name: Chang-tou-bi-sa Japanese name: Tengu herazame ( Figures 7–12 , Table 2 )

Apristurus longicephalus Nakaya, 1975: 32 , figs. 15–16 (original description, type locality: Japan); Compagno, 1984: 271 (description, Japan); Nakaya, 1984: 4, pl. 3-D (description, Japan); Nakaya, 1984: 43 and 296, pl. 10 (description, Japan); Nakaya, 1988a: 431, figs. 1–13 (description, Japan); Nakaya, 1988b: 134 (comparative materials, Japan); Compagno, 1988: 170 (taxonomic coments); Nakaya, 1991: 999 (comparative materials, Japan); Last and Stevens, 1994: 180 (description, Japan, China, Taiwan, Philippines, Australia, and Seychells); Compagno, 1999: 478 (checklist); Nakaya & Sato, 1999: 315 (taxonomic comments); Nakaya & Séret, 1999: 307 (comparative materials), Yoshino & Aonuma, 2002: 130 (key to species, Japan); Compagno et al., 2005: 194, pl. 32 (description, Japan, China, Taiwan, Philippines, Australia, and Seychelles); Iglésias et al., 2005a: 417 (description, East China, Japan, Seychelles, Mozambique, New Caledonia, and Australia); Iglésias et al., 2005b: 574 (molecular phylogeny, New Caledonia); Last & Stevens, 2009: 191, figs.11, 31.4 (description, East China Sea, Japan, Seychelles, Mozambique, Philippines, New Caledonia, and Australia); Ebert et al., 2013: 292, pl. 37 (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

Material examined. Taiwan: ASIZP 64264, female, 258 mm TL, 25°13.61’N, 122°49.5’E (East of Keelung), 992 m depth. Other regions (type specimen): HUMZ 42399 (holotype), hermaphroditic female, 367 mm TL, Tosa Bay, Kochi Prefecture, Japan (33°13’N, 133°44.4’E), 610–740 m depth. Other regions (non types): BSKU 22338, hermaphroditic female, 328 mm TL, Kochi Prefecture, Japan. BSKU 23012, male, 424 mm TL, Kochi Prefecture, Japan, 615 m depth. BSKU 26358, hermaphroditic female, 270 mm TL, 1000–1140 m depth, BSKU 26455, hermaphroditic male, 326 mm TL, 910–990 m depth, BSKU 26512, hermaphroditic male, 310 mm TL, 680-770 m depth, BSKU 26648, hermaphroditic female, 312 mm TL, BSKU 26649, hermaphroditic female, 280 mm TL, BSKU 26650, hermaphroditic male, 278 mm TL, BSKU 26651, hermaphroditic female, 386 mm TL, 900 m depth, BSKU 26867, male, 295 mm TL, BSKU 26868, hermaphroditic female, 412 mm TL, 750–760 m depth, 4 Feb. 1978, BSKU 27596, male, 417 mm TL, 610–640 m depth, BSKU 28096, hermaphroditic female, 336 mm TL, BSKU 28097, female, 390 mm TL, 820–830 m depth, BSKU 28166, hermaphroditic female, 311 mm TL, 908–915 m depth; BSKU 33519, hermaphroditic female, 411 mm TL, BSKU 33520, hermaphroditic female, 403 mm TL, 780–810 m depth; BSKU 33999, hermaphroditic female, 362 mm TL, BSKU 34000, hermaphroditic female, 413 mm TL, 600–620 m depth, Okinawa Trough, Japan. HUMZ 145151, hermaphroditic male, 380 mm TL, HUMZ 145153, female, 331 mm TL, East China Sea, depth unknown; HUMZ 145154, hermaphroditic female, 500 mm TL, East China Sea, depth unknown. HUMZ 191310, hermaphroditic female, 349 mm TL, 547–567 m depth, HUMZ 193669, male, 435 mm TL, 516–523 m depth off Sumatra, Indonesia. HUMZ 194156, hermaphroditic female, 358 mm TL, HUMZ 194157, hermaphroditic female, 321 mm TL, HUMZ 194158, hermaphroditic female, 375 mm TL, HUMZ 194159, hermaphroditic female, 315 mm TL, HUMZ 194161, male, 418 mm TL, 684–693 m depth, off Jakarta, Indonesia. HUMZ 194265, female, 473 mm TL, HUMZ 194266, female, 412 mm TL, 820–860 m depth. PPSI 317, male, 585 mm TL, 800–1350 m depth, PPSI 330, male, 327 mm TL, 810 m depth; PPSI 341, female, 507 mm TL, 790–820 m depth, PPSI 353, male, 405 mm TL, 820–900 m depth, southeast of Seychelles. ISH 376, male, 290 mm TL, 900–950 m depth, ISH 377, female, 237 mm TL, 980–1000 m depth, Mozambique.

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; P1–P2 space shorter than anal-fin base length (ceratotrichia); pectoral-fin tip always extending beyond midpoint of P1–P2 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.

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 gill slits present; fourth gill slit above pectoral-fin origin; fifth gill slit smallest above pectoral fin base. Gill septa with projection, covered with dermal denticles. Abdomen short; P1–P2 space shorter than anal-fin base length (ceratotrichia); pectoral-fin tip always extending beyond midpoint of P1–P2 space. Pectoral fin relatively large, broad, sub-triangular; outer margin parallel to inner margin. Pelvic fin low and long, its length subequal to or slightly greater than P1–P2 space. Dorsal fins similar in shape. First dorsal fin smaller than second; origin above posterior half of pelvic-fin base; insertion slightly posterior to anal-fin origin. Second dorsal-fin origin above middle of anal-fin base; insertion anterior to anal-fin insertion. Anal fin low, with a base much longer 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 slender; ventral lobe high but not produced: apex of ventral lobe rather rounded; subterminal notch distinct; length of terminal lobe twice caudal terminal lobe height. Caudal peduncle height subequal to pre-outer nostril length. Duodenum very long, length almost equal to valvular intestine ( Figure 8 ).

Intestinal spiral valves 13–17. Monospondylous vertebrae 29–33; precaudal diplospondylous vertebrae 26–35.

Teeth numerous and small, 35–45 rows on upper jaw, 29–40 rows on lower jaw with one long central cusp and short lateral cusps; usually one (sometimes two) lateral cusp on anterior upper jaw teeth and usually two (sometimes one) on posterior upper jaw and lower jaw teeth.

Egg capsule unknown.

Dermal denticles from dorso-lateral side of body small ( Figure 9 ), 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 caudal fin. Dermal denticles densely present around gill slits and on gill septa.

Clasper stout at base ( Figure 10 ), tapering posteriorly. Ventral and outer sides of surface densely 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 broad and deep; exorhipidion simple in shape, lacking free posterior end.

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

Size. Maximum size 585 mm TL in male ( Figure 11 ). Males less than 367 mm TL in maturity stage 1 (immature) with short claspers, less than 2.6 % TL. Males in 358–424mm TL in maturity stage 2 (adolescent) with developing but soft claspers. Males more than 434.5 mm TL in maturity stage 3 (adult) with long, well developed and hardened claspers. Females less than 361.5 mm TL in maturity stage 1. Females in 368–411 mm TL in maturity stage 2. Females more than 472.5 mm TL in maturity stage 3.

Distribution. Tosa Bay, East China Sea (Okinawa Trough), Taiwan, and China, Philippines, Indonesia (off Jawa and Sumatra), New Caledonia, Australia, Seychelles, and Mozambique, at depths of 516–1350 m ( Figure 12 ).

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. (2005b) 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. (2005b) found the holotype to have been an adolescent hermaphroditic “female” with a developing ovary. They also pointed out that the ratios of hermaphroditism in this species differed by region (i.e., 49 out of 50 specimens were hermaphroditic and only one was gonochoristic in New Caledonia, and 18 out of 22 specimens were hermaphroditic in Japanese waters, while all six specimens were gonochoristic in the Indian Ocean). The present specimen from Taiwan is a small “male” (255 mm TL) with undeveloped claspers, but its functional (true) sex could not be determined, because its internal sexual organs are not developed yet.

This is the first report of Apristurus longicephalus from Taiwan.

Figures

FIGURE 7. Apristurus longicephalus. A – B, ASIZP 64264, female, 258 mm TL, Keelung, Taiwan; C, Original drawing of holotype (from Nakaya, 1975); D – F, HUMZ 193669, male, 435 mm TL, Indonesia.

FIGURE 8. Digestive tract of Apristurus longicephalus (A, B) and A. herklotsi (C), showing duodenum (DU). A, holotype (HUMZ 42399); B, BSKU 27596; C, BSKU 27598. CS, cardiac stomach; IN, intestine; PA, pancreas; PS, pyloric stomach; RE, rectal gland.

FIGURE 9. Dermal denticles of Apristurus longicephalus, HUMZ 42399, holotype, hermaphroditic female, 367 mm TL. Scale bar = 0.5 mm.

FIGURE 10. Dorsal view of right clasper of Apristurus longicephalus, HUMZ 193669, male, 435 mm TL. CD, clasper denticles; ER, exorhipidion; PP, pseudopera; PS, pseudosiphon; PV, pelvic fin; RH, rhipidion. Scale bar = 1 cm.

FIGURE 11. Maturity stages of Apristurus longicephalus. Open symbols, males; solid symbols, females; grey symbols, unknown sex. Asterisk indicates holotype.

FIGURE 12. Distribution of Apristurus longicephalus. Star, holotype; circle, non-types.

Tables

TABLE 2. Proportional measurements and counts of Apristurus longicephalus.

TL (mm)	258	367	270–500
Proportion (%TL)
PreD2-origin length	53.5	55.6	53.1–62.5
PreD1-origin length	41.9	45.8	41.3–49.1
PreP1 length	23.3	25.7	22.5–27.6
PreP2 length	37.2	38.8	34.9–46.0
Preanal length	46.1	48.4	44.6–52.8
Precaudal length	61.6	62.7	56.2–69.1
Pre-branchial length	18.4	21.3	18.0–22.9
Pre-orbital length	12.1	13.2	10.0–13.7
Pre-outer nostril length	7.3	7.9	5.9–7.9
Pre-inner nostril length	8.3	9.6	7.7–10.2
Pre-oral length	9.6	11.6	9.0–11.9
Head length	23.2	22.3	22.8–27.3
Mouth width	7.2	8.7	4.9–7.9
Internarial width	4.6	4.6	3.5–4.6
Upper labial furrow length	3.3	3.4	2.9–3.7
Lower labial furrow length	2.7	2.8	1.7–3.4
Orbital length	2.6	3.0	2.4–3.5
Nostril length	2.4	3.1	1.9–3.5
Interorbital width	―	6.5	3.7–6.6
1st gill height	―	―	1.1–2.6
3rd gill height	―	1.8	1.5–3.3
5th gill height	―	―	1.3–2.5
D1-D2 space	6.9	6.0	4.5–8.3
D1-D2 origins	10.7	―	10.0–13.5
D1-D2 insertions	14.3	12.7	10.3–14.8
P1-P2 space	7.3	14.8	5.4–11.2
P1 tip to P2 origin	1.7	―	0.5–5.8
P1-P2 origins	13.8	14.8	11.7–17.9
D1 base length	4.4	4.7	4.0–8.0
D1 height	1.4	1.6	1.1–2.3
D1 free lobe length	2.5	―	2.1–3.6
D2 base length	6.8	6.3	3.3–7.9
D2 height	2.6	2.4	2.1–3.0
D2 free lobe length	3.6	―	2.6–6.1
P1 anterior margin		―	7.8–12.3
P2 length	8.7	10.0	5.5–9.7