Bathyraja pacifica, Last, Peter R., Stewart, Andrew L. & Séret, Bernard, 2016

Last, Peter R., Stewart, Andrew L. & Séret, Bernard, 2016, A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific, Zootaxa 4132 (1), pp. 107-117 : 108-115

Bathyraja pacifica sp. nov.

( Figs. 1–7 ; Table 1 )

Bathyraja sp.: Last in Williams, Gowlett-Holmes & Althaus, 2006 (photographs). Bathyraja sp.: Francis & Lyon, 2012: 70 (annotated checklist).

Bathyraja sp.: Stewart & Last, 2015: p. 186, fig 32.4 (description, figure), p. 181 (key).

Holotype. NMNZ P39707, adult male 1224 mm TL, western Norfolk Ridge, New Zealand (35° 37’ S, 169° 35’ E), RV Tangaroa , NORFANZ TAN 0308/167, demersal trawl, 1760–1789 m, 5 Jun 2003.

Diagnosis. A large species of Bathyraja (to 122 cm TL) with the following combination of characters based on the holotype (unique specimen): disc strongly depressed and quadrangular with narrowly rounded apices, width 64% TL, 1.1 times its length; tail rather short, length 0.8 in distance from snout tip to rear of cloaca, its width 1.8 times height at its midlength, 1.5 times at first dorsal-fin origin; pre-upper jaw length 18% TL, 2.3 times internasal width; ventral head length 32% TL; snout long, broad, length 4.0 times interorbital width, supported by slender flexible median cartilage; snout angle 83°; mouth narrow 7% TL; orbit diameter 57% interorbital width; first dorsal-fin height 1.7 in its base length; procaudal length 2.3 times first dorsal-fin base length, 4.8 times caudal-fin length; dorsal disc almost entirely devoid of fine denticles; no thorns on disc, other than narrow alar thorn patches; tail with 16 (one lost) thorns in single median row; total pectoral radials 84–85; trunk centra 34; predorsal centra 105; total centra ~136; tooth rows in upper jaw 29; skin thin and almost entirely translucent white, no dark areas on body, sensory pores indistinct (not dark edged).

Description. Disc broadly quadrangular, 1.08 times as broad as long in adult male holotype; maximum angle in front of spiracles 83°; axis of greatest width 61% of disc length; anterior margin weakly undulate, most strongly concave beside gill slits, almost straight anteriorly; pectoral apex narrowly rounded but not angular; posterior margin weakly to moderately convex; free rear tip very broadly rounded; inner margin concave near insertion of pectoral fin. Head moderately elongate, dorsal length 24.9% TL; preorbital length 7.15 times orbit length, 4.04 times interorbit; pre-upper jaw length 2.29 times internarial distance. Rostral lobe short, produced slightly, broadly and bluntly rounded; no fleshy process at apex. Orbit very small, diameter 0.57 times interorbital width; barely elevated above head; interorbital space moderately concave. Spiracular opening small, extending slightly forward of posterior margin of eye; main pore small, suboval, length 1.26 in orbit diameter; slit oblique. Nostril irregular, distorted; lateral nasal flap well expanded, its lateral margin forming a well-developed semi-circular tube; anterior margin of lateral nasal flap partly concealed beneath nasal curtain, mesial margin directed medially and abutting nasal curtain. Nasal curtain well developed, relatively broad and short; lateral margin strongly notched beside lateral nasal flap, notched near its midlength, then expanded posteriorly; broadly rounded distally, posterior margin of lobes very short, with sparse, thick fringe; internarial distance 1.84 in distance between first gill slits, 1.23 in distance between fifth gill slits. Upper jaw weakly arched, barely at symphysis; lower jaw weakly convex; lateral teeth of upper jaw exposed, not concealed by lip or lobe of nasal curtain. Teeth unicuspid, 29 rows in upper jaw, 29 rows in lower jaw; with slightly elevated subcircular bases; arranged in obvious longitudinal rows rather than in quincunx; cusps near middle of both jaws short, slender, pungent, strongly directed lingually in middle of upper jaw; slightly oblique (posterolaterally) at corner of jaws.

Pelvic fins moderate-sized, strongly notched (two smaller fleshy lobes in notch); anterior lobe relatively short, thallate, narrowly rounded distally, its lateral margin entire, convex in lateral profile. Posterior pelvic-fin lobe length 17.1% TL; much larger than, 1.59 times length of anterior lobe; with strongly convex lateral margin and subacute rear tip, profile irregular; inner margin short, almost straight. Clasper very elongate and slender, weakly to moderately depressed, in adults postcloacal length 24.0% TL; glans relatively small, distal, expanded slightly; dorsal lobe components consist of large proximal cleft and pseudorhipidion; ventral lobe components consist of large projection and disc-shaped spike; pseudosiphon well developed, dermal denticles absent.

Tail fleshy basally, moderately depressed anteriorly, relatively narrow at base; middle of tail subtriangular dorsally, weakly convex ventrally; lateral margins tapering gradually distally, not expanded forward of first dorsalfin base; tapering slightly more rapidly to tail tip beneath dorsal fins; width at insertions of pelvic fins 1.79 times width at midlength of tail and 3.52 times width at first dorsal-fin origin; length from rear of cloaca 0.83 times distance from tip of snout to rear of cloaca; width 1.54 times height at insertion of pelvic fin 1.79 times height at midlength, 1.51 times height at first dorsal fin origin; side of tail not strongly angular. Lateral tail fold well developed, long-based, weak anteriorly becoming broader posteriorly; originating above pelvic fin as a low ridge, forming a fold near mid-length of tail, terminating abruptly immediately before tail tip, notably broadest beneath base of second dorsal fin (its greatest width at second dorsal-fin origin subequal to tail width at origin of this fin). Dorsal fins of medium-size, of similar shape; first dorsal fin relatively tall, broadly lanceolate, of similar height but notably longer than second, its height 1.73 in its base length; fins tilted slightly with moderately elongate bases; anterior margins of both fins oblique, almost straight to convex; apices and posterior margins broadly rounded; free rear tip somewhat angular; inner margins similarly elongate, oblique, directed strongly anteroventrally from rear tips; second dorsal-fin base much shorter than first dorsal-fin base; interdorsal space moderate 7.20 times in first dorsal-fin base length; distance from first dorsal-fin origin to tail tip 2.30 times dorsal-fin base length, 4.76 times caudal-fin length; first dorsal-fin base 2.06 times caudal-fin length. Epichordal caudal-fin lobe very short, low, its height exceeding half tail width at fin origin; tallest at its midlength; its dorsal margin strongly convex; connected sub-basally to second dorsal fin; hypochordal caudal-fin lobe rudimentary, length less than a quarter first dorsal fin height.

Dorsal surface of disc with thorns confined to alar region; absent from rostral, orbital, spiracular, mid-disc, malar, scapular and nuchal regions; alar patches small, 33 thorns on left side, 29 on right side, in 3–4 narrow, longitudinal rows, in semi-regular patch near submargin of pectoral-fin apex; skin otherwise almost entirely naked.

Alar thorns slender, recurved, non-retractable; variably directed, mainly medially, but also laterally and posteromedially. Dorsal surface of tail with single, continuous row of 16, large predorsal median thorns, originating well behind level of cloaca and ending just forward of origin of first dorsal fin; no interdorsal thorns. Tail thorns robust, narrowly subconical, upright; very broad based (to 11.5 mm long, 7.5 mm high) with narrow pungent and weakly recurved tips, often broken; tips directed posteriorly; bases more or less equally spaced; not markedly decreasing in size posteriorly; much larger than alar thorns.

Denticles poorly developed, very small, very sparse, widely spaced; on disc confined to narrow, barely detectable submedian bands (divided either side of midline); similar patches extending along lateral regions of tail above skin fold to first dorsal-fin base; anterolateral edges of disc naked; denticles present on dorsal fins, densest anteriorly; no denticles around thorns of dorsal midline of tail or on midline of disc; absent from skin folds, pelvic fins, claspers. Ventral surface of disc and tail entirely naked.

Meristics: Tooth rows in upper jaw 29; lower jaw 29. Pectoral-fin propterygial radials 35; mesopterygial radials 20–21; metapterygial radials 28–30; total radials 84–85. Pelvic-fin radials males 1 + 18–19. Trunk centra 34 predorsal caudal centra 71; predorsal total centra 105; centra between origins of dorsal fins 12; diplospondylous centra ~102; total centra ~136.

Bathyraja pacifica Bathyraja richardsoni Bathyraja shuntovi Holotype Min Max Min Max Total length (mm) 1224 1383.0 1655.0 295.0 1122.0 ......continued on the next page Bathyraja pacifica Bathyraja richardsoni Bathyraja shuntovi Colour (fresh). Skin surfaces pale and somewhat translucent. Dorsal disc, tail and fins almost entirely translucent white (pink areas probably related to integumental damage); orbital membranes pale blue; tail thorns pale greyish; clasper off white with faint dusky tint dorsally. Ventral surface of disc and pelvic fins uniformly translucent white; some bluish areas beneath skin, reddish areas around mouth probably relate to bleeding, and posterior tail with some small, faint greyish patches. Preserved condition similar, some internal structures partly visible through transparent skin.

Size. Adult male holotype 1224 mm TL; no other material available.

Distribution. Deep insular slope of the western Norfolk Ridge, New Zealand (35°37’ S, 169°35’ E), in depths of 1760–1789 m. Stewart & Last (2015) report on four other Bathyraja specimens taken on the Macquarie Ridge and Campbell Plateau at 1247–1642 m depths. Re-examination of that material indicates that these probably represent other undescribed taxa, to be dealt with in a later publication.

Etymology. Epithet based on the distribution of this species near the western rim of the Pacific Ocean. Vernacular name: Pacific Blonde Skate.

Remarks. Bathyraja pacifica sp. nov. is unique within the genus in being entirely white (with partly translucent skin) all over both surfaces of the disc, tail and fins. Of the Bathyraja species occurring in the South- West Pacific, B. pacifica most closely resembles B. shuntovi in body shape (i.e. having a strongly depressed, pale quadrangular disc with a long triangular snout). However, B. pacifica has a broader interorbit (width ~4.6% vs. 3.2–3.9% TL in B. shuntovi ) and larger oronasal structures (e.g. mouth width ~7.0% vs. 5.3–6.6% TL; internasal distance ~8.0% vs. 5.8–7.3% TL; nasal curtain width ~9.0% vs. 7.2–8.0% TL). The snout and head are also relatively longer in adults of B. pacifica . Bathyraja richardsoni is a much heavier bodied skate with a much broader interorbit (width 7.4–7.7% vs. ~4.6% TL in B. pacifica ) and shorter snout (length 13.2–13.9% vs. ~18.7% TL). Bathyraja leucomelanos is pale on the dorsal surface but dark ventrally (rather than being uniformly pale over the entire body) and its disc is much narrower (width ~63.9% vs. ~68.5% TL).

Scientific exploration in the lower slope (> 1600 m) to abyssal regions in the New Zealand EEZ has been very sporadic and the fauna of those regions remains largely unknown. As more opportunities arise to sample these depths, it is expected that more new records and new, undescribed fishes, including skates, will be caught.

Of other Bathyraja species, B. pallida (Forster, 1967) from the North Atlantic can be almost white on the dorsal surface but is brownish ventrally (rather than whitish), and its snout is more broadly pointed and relatively shorter (length less than 6 times orbit length vs. more than 7 times in B. pacifica ).

Figures

FIGURE 1. Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL, fresh coloration): A, dorsal surface; B, ventral surface.

FIGURE 2. Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL, preserved coloration) showing dorsal snout, orbito-spiracular and nuchal regions.

FIGURE 3. Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL, preserved coloration) showing the oronasal region and tooth bands.

FIGURE 4. Radiograph of the head of Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL).

FIGURE 5. Median thorns and rudimentary denticles at the tail midlength of Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL). A. Dorsal view. B. Lateral view.

FIGURE 6. Lateral view of the dorsal and caudal fins of Bathyraja pacifica sp. nov., adult male holotype (NMNZ P 39707, 1224 mm TL).

FIGURE 7. Map of the New Zealand Exclusive Economic Zone showing the collection location of the holotype of Bathyraja pacifica sp. nov., in the northern Tasman Sea.

Tables

TABLE 1. (Continued)

Holotype	Min	Max	Min	Max
Width of first gill opening 1.0	1.6	2.0	0.9	1.3
Width of fifth gill opening 1.0	1.3	1.6	0.6	0.9
Distance between first gill openings 14.7	19.5	19.8	12.1	14.3
Distance between fifth gill openings 9.8	15.2	15.4	9.0	9.9
Clasper-post cloacal length 24.0	17.3	19.7	7.2	8.3
Length of anterior pelvic lobe 10.8	7.7	9.1	10.4	13.0
Length of posterior pelvic lobe 17.1	14.6	15.5	14.2	14.9
Pelvic base - width 7.2	9.1	10.5	6.7	9.3
Tail at axil pelvic fins - width 4.2	4.3	5.8	3.3	4.2
Tail at axil pelvic fins - height 2.7	2.9	3.4	2.0	2.7
Tail at midlength - width 2.4	1.8	1.9	1.6	2.1
Tail at midlength - height 1.3	1.4	1.6	1.0	1.5
Tail at D1 origin - width 1.2	1.4	1.5	1.2	1.4
Tail at D1 origin - height 0.8	1.1	1.2	0.8	1.0
D1 base - length 3.8	3.2	3.2	3.5	4.6
D1 - height 2.2	1.4	1.6	1.6	1.9
D1 orig to caudal fin tip 8.8	11.6	11.6	9.0	14.5
D2 orig to caudal fin tip 4.5	6.9	7.5	5.4	8.3
caudal fin length 1.9	3.3	3.7	2.4	3.7