Apristurus macrostomus Chu, Meng

Nakaya, Kazuhiro & Kawauchi, Junro, 2013, A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters, Zootaxa 3752 (1), pp. 130-171 : 153-161

Apristurus macrostomus Chu, Meng & Li, 1985

English name: Broad-mouth catshark Taiwanese name: Da-ko-bi-sa

Japanese name: Ryukyu herazame

( Figures 22–30 , Table 4 )

Apristurus macrostomus Chu, Meng & Li, 1985 in Meng, Chu & Li, 1985: 45, fig. 2 (original description, type locality: China); Compagno et al., 2005: 195, pl. 31 (description, China); Ebert et al., 2013: 293, pl. 39 (description). Apristurus macrorynchus: Chen, 1963 , 33, fig. 11 (description, Taiwan); Chen & Joung in Shen et al., 1993: 53, pls. 5–7 (description, Taiwan); Shen & Wu, 2011: 63 (description, Taiwan).

Apristurus platyrhynchus: Shen & Wu, 2011: 63 (description, Taiwan).

Material examined. Taiwan: NMMBP 7457, 307 mm TL, female, 347 mm TL, male, NMMBP 7458, 316 mm TL, female, 344 mm TL, male, NMMBP 7497, 203 - 429 mm TL, 1 male and 2 females, NMMBP 12052, 309 mm TL, male, 318 mm TL, male, 333 mm TL, female, NMMBP 12055, 420 mm TL, male, Da-xi. NMMBP 13718, 325– 456 mm TL, 4 males and 1 female, Dong-gang. NMMBP 14837, 249 mm TL, male, NMMBP 16546, 286 mm TL, female, 370 mm TL, male, Da-xi. NMMBP 17561, 465 mm TL, male. HUMZ 170355, male, 421.5 mm TL, HUMZ 170356, male, 292.1 mm TL, HUMZ 170357, male, 285.2 mm TL, HUMZ 170358, male, 414.8 mm TL, HUMZ 170387, female, 348.9 mm TL, HUMZ 170388, female, 266.1 mm TL, HUMZ 170389, female, 318.0 mm TL, HUMZ 170390, male, 266.3 mm TL, HUMZ 170392, male, 369.8 mm TL, HUMZ 170393, female, 210.1 mm TL, HUMZ 170394, female, 226.3 mm TL, HUMZ 170450, female, 352.1 mm TL, HUMZ 170451, female, 334.0 mm TL, HUMZ 170452, female, 351.9 mm TL, HUMZ 170453, female, 386.4 mm TL, HUMZ 170454, male, 411.3 mm TL, HUMZ 170485, male, 486.9 mm TL, HUMZ 170486, female, 473.8 mm TL, HUMZ 170478, female, 328.2 mm TL, HUMZ 170488, male, 388.6 mm TL, HUMZ 170489, female, 282.2 mm TL, HUMZ 170929, male, 373.4 mm TL, HUMZ 170930, male, 252.5 mm TL, HUMZ 170931, female, 259.2 mm TL, HUMZ 170933, male, 282.1 mm TL, HUMZ 170965, female, 322.1 mm TL, HUMZ 171435, female, 332.5 mm TL, HUMZ 170436, female, 341.0 mm TL, HUMZ 170437, male, 316.9 mm TL, HUMZ 171438, female, 251.8 mm TL, HUMZ 185163, male, 340.1 mm TL, HUMZ 185164, male, 348.3 mm TL, HUMZ 185165, male, 325.0 mm TL, HUMZ 185166, male, 295.7 mm TL, HUMZ 185167, male, 366.2 mm TL, HUMZ 185168, male, 326.5 mm TL, HUMZ 185171, male, 316.7 mm TL, HUMZ 185172, male, 334.5 mm TL, HUMZ 198612, male, 468 mm TL, Da-xi fishing port, collected from around Kuei-Shan Island, Taiwan. Other regions (type specimen): SCSFRI D 0 0 807 (holotype of A. macrostomus ), male, 389 mm TL, off the estuary of Pearl River, South China Sea, China, 913 m depth. Other regions (non types): BSKU 15546, female, 194.5 mm TL, Sulu Sea, Philippines, 495 m depth, 500 m depth. BSKU 29574, female, 475.0 mm TL, Okinawa Trough, Japan, 220 m depth. BSKU 32566, male, 439 mm TL, Okinawa Trough, Japan, 600 m depth. BSKU 43664, female, 573.1 mm TL, Mimase, Kochi Prefecture, Japan. HUMZ 191137 and HUMZ 191138, 1 male and 1 female, 324–329 mm TL, off Sumatra Island, Indonesia, 547–567m depth. HUMZ 191416, male, 406 mm TL, off Jawa Island, Indonesia, 850–916 m depth, 12 Sep. 2004. HUMZ 191498, male, 451 mm TL, 989– 850 m depth; HUMZ 191531, female, 436 mm TL, HUMZ 193968, female, 432 mm TL, 516–523 m depth, off Sumatra Island, Indonesia. HUMZ 194139 and 194140, 1 male and 1 female, 385-439 mm TL, 570–601 m depth, HUMZ 194160, male, 166 mm TL, 684–693 m depth, HUMZ 194448, female, 382 mm TL, 600–620 m depth, off Jawa Island, Indonesia. HUMZ 194668, female, 477 mm TL, 784– 780 m depth, HUMZ 194676 and 194677, 1 male and 1 female, 440–457 mm TL, 561- 526 m depth, off Sumatra Island, Indonesia. PPSI 15 (2 specimens), 1 male and 1 female, 390–400 mm TL, Sumatra Island, Indonesia, 800m depth. SCSFRI 800546, female, 435.7 mm TL, corresponds to the continental shelf, South China Sea, China, 200–2000 m depth. USNM 168185, male, 142.3 mm TL, Philippines.

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 behind pelvic fin base or above anterior half of P2– anal space: second dorsal-fin insertion anterior to anal-fin insertion; snout rather long; tip bell-shaped; abdomen short; P1–P2 space much shorter than anal-fin base length (ceratotrichia); pectoral-fin tip always extending beyond midpoint of midpoint of P1–P2 space; intestinal spiral valves 18–21; monospondylous + precaudal diplospondylous vertebrae 33–37 + 31–40; clasper hook present on edge of exorhipidion; maturing size around 40 cm TL in both sexes.

Description. Proportional measurements and meristic counts are given in Table 4 . Body cylindrical, slender and elongate ( Figure 22 ). Head dorso-ventrally flattened, posterior part of body compressed laterally. Snout rather long; tip ball-shaped. Pre-outer nostril length 1.3–1.9 times internarial width. Pre-oral length slightly less than pre-orbital length, 2.5–3.4 times internarial width, subequal to mouth width and greater than interorbital width. Pre-orbital length 1.7–2.1 times interorbital length, 2.9–4.2 times orbit length. Internarial width subequal to orbit length and nostril width. Nostril relatively large, expanding obliquely inward from snout edge; length about half of pre-inner nostril length. Nostril-mouth space about half of internarial width. Mouth broadly arched, with well developed labial furrows; upper labial furrows 1.1–1.6 times longer than lower one. Upper labial furrow reaching beyond midpoint between mouth corner and posterior margin of nostril. Orbit narrow 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 projection, densely covered with dermal denticles. Abdomen short; P1–P2 space much shorter than anal-fin base length (ceratotrichia); pectoral-fin tip always reaching beyond midpoint of P1–P2 space. Pectoral fin relatively large, wide, subtrianglular; outer margin nearly parallel to inner margin. Pelvic fin relatively low and long, length subequal to preorbital length. Dorsal fins similar in shape. First dorsal fin smaller than second; origin behind pelvic fin base or above anterior half of P2–anal space; insertion above anal-fin origin. Second dorsal-fin origin above middle of anal-fin base; insertion anterior to anal-fin insertion. Anal fin low, triangular, 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 slightly produced: apex of ventral lobe rather rounded; subterminal notch distinct; length of terminal lobe twice caudal terminal lobe height. Caudal peduncle height 0.5– 0.9 times pre-outer nostril length. Duodenum very short.

Intestinal spiral valves 18–21. Monospondylous vertebrae 31–37; precaudal diplospondylous vertebrae 31–40.

Teeth numerous and small, 62–86 rows on upper jaw, 55–81 rows on lower jaw with one long central cusp and one to two short lateral cusps.

Egg capsule taken from 477 mm TL specimen (HUMZ 194668) short and stocky ( Figure 23 ), 69.7 mm long and 23.8 mm wide, with fibrous thread on anterior ends and coiled tendrils on posterior ends; anterior margin of the capsule rounded without fibrous thread at each corner; lateral edges flanged; posterior tip separated with tendrils. Surface of egg capsule with no ridges. Color yellowish.

Dermal denticles from dorso-lateral side of body small ( Figure 24 ), 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 25 ). 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 present on edge of exorhipidion; pseudosiphon rounded hole-like in shape; cover rhipidion vestigial; pseudopera broad and deep; exorhipidion simple in shape, without free posterior end.

Color. Upper and lower surfaces of body and fins uniformly grey to dark brown with blackish naked areas along the fin margins. Tongue and palate blackish brown, peritoneum white.

Size. Maximum size 495 mm TL in male, and 573.1 mm TL in female ( Figure 26 ). Most males less than 388.6 mm TL in maturity stage 1 (immature) with short claspers, less than 3.7% TL. Males in 377–414.8 mm TL in maturity stage 2 (adolescent) with developing but soft claspers. Most males more than 385 mm TL in maturity stage 3 (adult) with long, well developed and hardened claspers. All females less than 348.9 mm TL in maturity stage 1. Females in 382–400 mm TL in maturity stage 2. All females more than 432 mm TL in maturity stage 3.

Distritbution. Japan (northward to Kochi, East China Sea (Okinawa Trough), Taiwan (Da-xi, Kaohsiung, Donggang), China (South China Sea), Philippines, and Indonesia (Sumatra Island) ( Figure 27 ), at depths of 220–1069 m.

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

Apristurus macrostomus has not formerly been reported from the waters of Taiwan, because this species has been confused with A. macrorhynchus and A. platyrhynchus (Chen, 1963; Shen &Wu, 2011). Actually, this species resembles these two species in having rather long snout, and narrow interspace between pectoral and pelvic fin bases. However, A. macrostomus is distinguishable from A. macrorhynchus , which is currently not reported from Taiwan, by having a much smaller first dorsal fin as compared with the second dorsal fin (slightly smaller in A.

macrorhynchus ), first dorsal fin originating behind the pelvic fin base (above or before pelvic fin insertion in A. macrorhynchus ), and by having fewer vertebrae (more in A. macrorhynchus ; Figure 28 ).

A. macrostomus

Taiwan Holotype Other regions 26 males, 20 females male 9 males, 12 females P1 anterior margin 9.1–12.4 13.9 9.8–14.7

...... continued on the next page A. macrostomus

Taiwan Holotype Other regions

26 males, 20 females male 9 males, 12 females P2 length 8.7–12.1 11.3 10.2–12.7 Anal base length (ceratotrichia) 14.7–18.9 15.9 13.4–19.2 Anal height (muscle) 2.6–5.1 4.5 3.1–5.1 Caudal length 29.4–33.9 31.4 29.9–35.2 Clasper outer length 1.5–6.0 6.0 1.4–6.2 Counts

Tooth rows:

upper 63–86 76 62–84

lower 55–80 73 65–81 Vertebrae:

monospondylous 34–37 ― 31–36

precaudal diplospondylous 33–40 ― 31–37 Spiral valves 18–21 ― 18–21 Apristurus macrostomus and A. platyrhynchus are quite similar each other morphologically, but they are apparently different species. A. macrostomus is a small-sized species attaining up to 57 cm TL, and begins to mature at around 40 cm TL. On the other hand, A. platyrhynchus is a large-sized species attaining 80 cm TL, and becomes mature at around 60 cm TL ( Figure 29 ). In A. macrostomus , the egg capsule is short and stocky with long tendrils on the posterior end of the capsule ( Figure 23 ), whereas the egg capsule of A. platyrhynchus is very slender and long without tendrils ( Figure 32 ). The claspers are also different, with clasper hooks in A. macrostomus ( Figure 25 ), and without clasper hooks in A. platyrhynchus ( Figure 34 ). A. macrostomus has a relatively lower second dorsal fin ( Figure 30 ), and the origin of the first dorsal fin is located above the anterior half of P2–anal space, while A. platyrhynchus has a relatively higher second dorsal fin ( Figure 30 ), and the origin of the first dorsal origin is located above the middle of the P2–anal space.

Apristurus macrostomus and A. platyrhynchus can be primarily distinguished by total length and maturity. As shown in Figure 29 , the adolescent and mature individuals less than 55 cm TL could be identified as A. macrostomus . Immature individuals larger than 40 cm TL, adolescent individuals between 55 and 60 cm TL and the mature individuals larger than 60 cm TL could be identified as A. platyrhynchus . However, smaller individuals less than 40 cm TL includes both species and it is necessary to work on these specimens further in order to determine good discriminating characters.

Apristurus macrostomus is the most populous species of Apristurus in Taiwan, but it was incorrectly reported as A. macrorhynchus or A. platyrhynchus . Therefore, this is the first report of the species from Taiwan.

Figures

FIGURE 22. Apristurus macrostomus. A – C, NMMBP 17561, female, 465 mm TL, Taiwan; D, Original drawing of holotype, SCSFRI D- 00807, male, 389 mm TL, China (from Meng et al., 1985).

FIGURE 23. Egg capsule of Apristurus macrostomus taken from HUMZ 194668, female, 477 mm TL. Scale bar = 1 cm.

FIGURE 24. Dermal denticles of Apristurus macrostomus, HUMZ 194676, male. Scale bar = 0.5 mm.

FIGURE 25. Dorsal views of right clasper of Apristurus macrostomus, HUMZ 170485, male, 486.9 mm TL. CD, clasper denticles; CH, clasper hooks; ER, exorhipidion; PP, pseudopera; PS, pseudosiphon; PV, pelvic fin; RH, rhipidion. Scale bars = 5 mm.

FIGURE 26. Maturity stages of Apristurus macrostomus. Open symbols, males; solid symbols, females. Asterisk indicates holotype.

FIGURE 27. Distribution of Apristurus macrostomus. Star, holotype; circles, non-types.

FIGURE 28. Relation of monospondylous and precaudal diplospondylous vertebrae in Apristurus macrostomus (diamonds) and A. macrorhynchus (circles).

FIGURE 29. Maturity stage of Apristurus macrostomus (diamonds) and A. platyrhynchus (circles). Open symbols, males; solid symbols, females. Asterisk indicates holotype.

FIGURE 30. D 2 height in Apristurus macrostomus (diamonds) and A. platyrhynchus (circles). Solid symbols, specimens from Taiwan; open symbols, specimens from other regions. Asterisk indicates holotype.

FIGURE 32. Egg capsule of Apristurus platyrhynchus from TMFE 23, female, 651 mm TL. Scale bar = 1 cm.

FIGURE 34. Dorsal view of left clasper of Apristurus platyrhynchus, TMFE 520, male, 711 mm TL. CD, clasper denticles; ER, exorhipidion; PP, pseudopera; PS, pseudosiphon; PV, pelvic fin; RH, rhipidion. Scale bar = 1 cm.

Tables

TABLE 4. Proportional measurements and counts of Apristurus macrostomus.

TL (mm)	210–487	389	142–475
Proportion (%TL)
PreD2-origin length	59.1–63.1	59.6	55.6–62.3
PreD1-origin length	45.0–49.7	―	40.6–49.9
PreP1 length	21.3–23.7	23.4	20.2–24.1
PreP2 length	36.9–40.0	38.6	35.8–39.9
Preanal length	49.3–53.6	52.4	46.9–53.6
Precaudal length	66.1–71.1	67.4	65.1–70.0
Pre-branchial length	17.8–21.0	17.6	17.9–21.1
Pre-orbital length	10.4–11.7	9.6	9.6–12.3
Pre-outer nostril length	4.9–6.5	5.1	4.6–5.6
Pre-inner nostril length	8.0–9.5	8.0	6.9–9.1
Pre-oral length	9.0–11.6	8.9	8.6–11.0
Head length	21.8–24.6	20.9	21.7–25.7
Mouth width	7.3–9.7	―	6.7–9.3
Internarial width	3.1–4.0	3.6	3.1–4.1
Upper labial furrow length	3.0–3.9	4.7	2.7–4.0
Lower labial furrow length	2.2–3.0	2.5	1.9–3.4
Orbital length	2.7–3.4	3.9	2.5–4.4
Nostril length	3.5–4.6	3.5	3.4–4.9
Interorbital width	5.3–6.8	5.2	5.5–7.2
1st gill height	1.0–2.1	2.3	0.8–2.9
3rd gill height	1.5–2.6	2.4	1.4–3.2
5th gill height	1.2–2.2	1.9	1.5–2.9
D1-D2 space	7.3–10.6	5.5	8.1–10.6
D1-D2 origins	11.8–15.5	11.6	12.5–15.0
D1-D2 insertions	12.9–15.7	13.0	13.3–15.9
P1-P2 space	7.4–12.2	7.3	7.2–11.2
P1 tip to P2 origin	1.7–6.1	2.0	1.4–5.2
P1-P2 origins	14.4–18.8	13.7	13.4–20.7
D1 base length	3.5–5.8	5.6	3.8–7.2
D1 height	0.9–1.7	1.4	0.7–2.3
D1 free lobe length	3.3	3.1	2.8–3.7
D2 base length	4.7–6.5	7.1	5.0–8.4
D2 height	1.7–2.3	2.5	2.0–3.2
D2 free lobe length	3.4	3.6	3.2–4.6