Apristurus yangi, White, Mana & Naylor, 2017

WHITE, WILLIAM T., MANA, RALPH R. & NAYLOR, GAVIN J. P., 2017, Description of a new species of deepwater catshark Apristurus yangi n. sp (Carcharhiniformes: Pentanchidae) from Papua New Guinea, Zootaxa 4320 (1), pp. 25-40 : 26-33

Apristurus yangi n.sp.

Yang’s Longnose Catshark

Figs 1–9 ; Table 1

Holotype. ASIZ P0080718 , adult female 437 mm TL, Vitiaz Strait , Morobe Province, Papua New Guinea, 06°02.030' S, 147°37.490' E, 700–701 m depth, station number CP3723, 7 Oct 2010.

Paratype. NTUM 11491 (tissue accession GN17228), female 205 mm TL, northwest of Kavieng , New Ireland, Papua New Guinea, 02°20' S, 150°38' E, 630–786 m depth, station number CP4428, 29 Aug 2014.

Diagnosis. A long-snouted Apristurus with the following combination of characters: long and narrow head, head length 23.5–23.8% TL, interorbital space 5.8–6.7% TL; snout very elongate, preoral length 12.4–12.7% TL, preorbital length 12.6–12.9; mouth wide, its width 7.9–8.6% TL; pelvic–anal space 3.2–4.0% TL; anal fin relatively large, base length 14.9–15.4% TL; anal-fin posterior margin 11.0% TL; prepectoral length relatively long, about 22.3–23.5% TL; labial furrows long, not confined to mouth corners, uppers 3.7–3.8% TL; no enlarged denticles on upper or lower caudal fin; duodenum of intestine very short, 8 intestinal spiral valves; tip of snout blackish; 32–33 monospondylous centra; 38 precaudal-diplospondylous vertebrae; precaudal centra 70–71; females adult by 437 mm TL; egg case small (~ 5.9 cm long), with faint longitudinal striations.

Description. Body anterior to pelvic fins slender and cylindrical; height and width of body at the middle point of P1–P2 space almost equal ( Fig. 1 ). Abdomen narrow; P1–P2 space 9.7% TL in holotype (7.2% TL in paratype) much less than preorbital length, i.e. 12.6 (12.9)% TL and anal-fin base 14.9 (15.4)% TL. Posterior part of body compressed laterally; its width about half of its height. Snout extremely long and flattened dorsoventrally ( Fig. 2 ), pre-outer nostril length less than mouth width, i.e. 7.3 (7.0) vs. 7.9 (8.6)% TL), and 2.0 (1.6) times internarial width. Preoral length 3.4 (3.0) times internarial width, 4.7 (5.3) times mouth length, and 2.1 (1.9) times interorbital width. Preorbital length 2.2 (1.9) times interorbital width, 3.7 (3.7) times orbit length.

Nostril relatively large, expanding obliquely inward from snout edge; nostril width (0.9) 0.8 times internarial width, and subequal to orbit length. Mouth broadly rounded, width 3.0 (3.6) times mouth length; mouth length 0.7 (0.6) times upper labial furrow length. Upper labial furrows long, 1.5 (1.2) times lower furrows. Orbit large, its length subequal to nostril length, 0.6 (0.5) times interorbital width. Subocular fold present, but not conspicuous. Spiracle small, located just behind eye and about level with middle of eye. Five small gill slits; edges of gill septa and gill slits blackish; gill slits about equal in height, 5th situated above pectoral-fin base. Gill septa likely covered with numerous dermal denticles except posteriormost margins (denticles largely worn off in holotype).

Pectoral fin relatively large, broad, expanding laterally; anterior margin 1.3 (1.5) times P1–P2 space; its posterior tip extending to about an orbit length in front of pelvic-fin origin. Pelvic-fin origin located at mid-point between pectoral-fin insertion and anal-fin origin. Pelvic fin small, low, length subequal to P1–P2 space. Anal fin low, its height subequal to nostril length, base length 1.3 (1.6) times pectoral-fin anterior margin, 6.1 (4.2) times its height; its origin about an orbit length behind pelvic-fin insertion.

First dorsal fin located above pelvic–anal interspace; its origin just posterior to pelvic-fin insertion. First dorsal fin small, its height 0.7 (0.8) times second dorsal-fin height. Anterior margins of dorsal fins slightly convex; D1– D2 space subequal to second dorsal-fin base length. Second dorsal-fin insertion anterior to anal-fin insertion. Caudal fin long, without distinctively enlarged modified denticles on dorsal edge; ventral lobe high and its apex somewhat angular.

Tooth rows on upper jaw 67 (52), on lower jaw 59 (56). Teeth on upper jaw possessing 5 or 7 cusps, either 2– 1–2 or 3–1–3 arrangement; 3rd tooth from the symphysis with long central cusp, almost twice length of adjacent cusp; cusps becoming slightly posteriorly projecting from about 10th tooth from symphysis (posteriorly directing in anteriormost teeth also in smaller paratype). Teeth on lower jaw with 5–9 cusps, mostly 7 anteriorly; posteriormost teeth with numerous cusps in maple leaf-like outline (often with 9 cusps), its central cusp not conspicuously elongated. Number of tooth cusps on lower jaw usually more than those on upper jaw when compared at same position.

Denticles from dorsolateral side of body closely spaced, overlapping, leaf-like in shape with 3 cusps, central cusp about half length of crown ( Fig. 4 ); each cusp sharp and pointed with weak ridges on its dorsal surface; outer surface of denticles completely structured by reticulations. No modified or enlarged dermal denticles on the dorsal margin of caudal fin.

Single egg capsule from holotype: 59 mm long and 14 mm wide, narrow, cylindrical, without coiled tendrils on anterior and posterior ends ( Fig. 5 ); anterior margin of the capsule truncated without projection at each corner; weak neckline constriction located anteriorly at about one quarter of length down capsule; lateral edges flanged, fused at posterior end; posterior tip forming narrow tubule tapering toward its end. Surface of egg capsule relatively smooth to touch, but with longitudinal striations clearly visible under magnification ( Fig. 6 ). Colour brownish, eggs taken from oviduct covered with fibrous substance. Respiratory slits at anterior-left and posteriorleft side of the capsule; slits covered by thin membrane extended from edge.

Monospondylous centra 32 (33); precaudal diplospondylous centra 38 (38); precaudal centra 70 (71); caudal centra 58 (~61); total centra 128 (~132). Holotype with 8 intestinal spiral valves.

Colour. Colour in alcohol uniformly pale brownish; dorsal side of body a slightly darker than ventral side. Margin of snout tip blackish (more distinct in juvenile paratype). Fins anterior margins darker, most obvious on pectoral fins. Axils of dorsal, pectoral and pelvic fins naked with blackish coloration. Inside of buccal cavity dark blackish brown, without denticles.

Size and biology. Only known from the two female type specimens, 437 and 205 mm TL. The 437 mm TL holotype was a pregnant female containing a single egg capsule. The holotype contained a single, 73 mm SL lanternfish of the genus Myctophum .

Distribution. Type specimens collected from off Kavieng, New Ireland and from the Vitiaz Strait in Morobe Province of Papua New Guinea in depths of 630 to 786 m ( Fig. 7 ).

Etymology. Named for Dr Lei Yang whose extensive molecular phylogenetic work on sharks and rays has contributed toward an improved understanding of their alpha taxonomy and phylogenetic relationships.

Molecular analysis. The analysis of the NADH 2 data for the paratype (holotype tissue sample not available) suggests that Apristurus yangi represents a monophyletic lineage that is distinct from, but most closely related to Apristurus herklotsi from off Taiwan and Apristurus australis from off Australia ( Fig. 8 ). These three species are, in turn, sister to A. garricki from New Zealand. Apristurus longicephalus lies outside this group of four species and together these five species represent the longicephalus group within the genus Apristurus ( Fig. 8 ). It should be noted that this inference is based on a single mitochondrial marker and inclusion of multiple nuclear markers could affect the presented inference.

Figures

FIGURE 1. Lateral view of Apristurus yangi n. sp.: (A) holotype ASIZ P 0080718, adult female 437 mm TL; (B) paratype NTUM 11491, female 205 mm TL.

FIGURE 2. Head of Apristurus yangi n. sp., holotype (ASIZ P 0080718, adult female 437 mm TL); (A) lateral view; (B) ventral view.

FIGURE 3. Dentition of Apristurus yangi n. sp., holotype (ASIZ P 0080718, adult female 437 mm TL).

FIGURE 4. Dermal denticles of Apristurus yangi n. sp., holotype (ASIZ P 0080718, adult female 437 mm TL).

FIGURE 5. Egg capsule of Apristurus yangi n. sp. taken from holotype (ASIZ P 0080718, adult female 437 mm TL). Egg capsule length 59 mm.

FIGURE 6. Surface of egg capsule of Apristurus yangi n. sp. extracted from holotype (ASIZ P 0080718, adult female 437 mm TL).

FIGURE 7. Distribution of Apristurus species collected in Papua New Guinean waters. Yellow star and circle denotes A. yangi holotype and paratype, respectively; red denotes A. macrostomus specimens; green A. nakayai; and blue the unidentified short snouted species (Image © NASA, TerraMetrics, Google Earth).

FIGURE 8. Maximum Likelihood Tree under GTR + I + G mode using 1044 aligned sites from the mitochondrial NADH 2 gene. Bootstrap support values shown on internal branches when above 50 %.

FIGURE 9. Lateral view of: (A) Apristurus australis (CSIRO H 2356 - 01, male 530 mm TL); (B) Apristurus garricki (CSIRO H 6067 - 01, adult male 650 mm TL); (C) Apristurus herklotsi (NMMB-P HO- 198, female 475 mm TL).

Tables

TABLE 1. Morphometrical measurements of the holotype (ASIZ P 0080718) and paratype (NTUM 11491) of Apristurus yangi n. sp., and the second known specimen of Apristurus nakayai (NTUM 11488), expressed as a percentage of total length.

	A. yangi		A. nakayai
	Holotype	Paratype	n = 1
TL (mm)	437	205	559
PreD2-origin length	60.0	53.4	62.1
PreD2-insertion length	65.4	59.0	68.5
PreD1-origin length	48.7	43.4	47.4
PreD1-insertion length	53.1	48.3	52.6
Head length	23.8	23.5	22.1
Pre-branchial length	20.9	21.5	16.9
Pre-spiracular length	16.4	17.2	11.9
Pre-orbital length	12.6	12.9	7.8
Pre-outer nostril	7.3	7.0	4.5
Pre-inner nostril	9.5	10.1	6.4
Pre-oral length	12.4	12.7	8.1
PreP1 length	23.5	22.3	21.4
PreP2 length	39.7	33.6	37.2
Pre-vent length	44.9	41.0	41.9
Preanal length	52.6	44.9	47.4
Precaudal length	67.7	61.5	69.2
Head height	6.8	5.7	8.9
Head width (mouth corners)	8.6	9.7	9.8
Head width (max)	9.2	10.9	10.1
Mouth width	7.9	8.6	8.3
Mouth length	2.6	2.4	2.6
Internarial width	3.6	4.2	3.4
Upper labial furrow lendth	3.7	3.8	2.9
Lower labial furrow lendth	2.5	3.2	2.1
Orbit length	3.4	3.5	3.3
Orbit height	0.9	1.2	0.9
Nostril width	3.1	3.6	3.2
Nostril-mouth	2.9	2.7	1.7
Interorbital width	5.8	6.7	5.6
1 st gill height	1.4	1.5	1.5
3rd gill height	1.9	1.6	1.4
5th gill height	1.4	1.8	1.5
Intergill width	3.4	2.2	4.2
D1-D2 space	6.4	5.2	9.5
D1-D2 origins	11.4	9.8	14.3
D1-D2 insertions	12.3	10.7	15.8
P1-P2 space	9.7	7.2	8.4
P1 tip to P2 origin	2.7	2.4	2.1
P1-P2 origins	16.1	12.8	16.7