Bathyraja kincaidii ( Garman, 1908 )

Knuckey, James D. S. & Ebert, David A., 2022, A taxonomic revision of Northeast Pacific softnose skates (Rajiformes: Arhynchobatidae: Bathyraja Ishiyama), Zootaxa 5142 (1), pp. 1-89 : 25-32

Bathyraja kincaidii ( Garman, 1908)

Figures 17–20 ; Tables 4 , 8–9

Sandpaper Skate

Raja kincaidii Garman, 1908: 254 [Bulletin of the Museum of Comparative Zoology ] v. 51 (no. 9). Holotype: MCZ 1261 - S. Off Friday Harbor, Washington, USA. Type catalog: Hartel & Dingerkus, 1997: xlvii.

Raja kincaidii: Garman, 1908: 254 ; Garman, 1913: 343, pl. 17 (description); Schultz & DeLacy, 1935: 368 (record; range); Schultz, 1936: 132 (key); Schultz, 1937: 235 (description); Roedel & Ripley, 1950: 74 (description, range); Alverson, 1951: 86 (record); Clemens & Wilby, 196l: 88, fig. 27 (description, range); Grinols, 1965: 26 (listed); Miller & Lea, 1972: 44 (description, figure, key); Quast & Hall, 1972: 4 (listed); Hart, 1973: 58 (description, figure, range); Robins et al., 1980: 14 (listed); Del Moral-Flores et al., 2016: 110.

Breviraja kincaidii: Cox, 1963: 278 , fig. 6.

Bathyraja kincaidii: Stehmann, 1978: 53 (reference); Eschmeyer et al., 1983: 50, fig. 11, pl. 4 (description); Compagno, 1999: 488 (listed); Ebert, 2003: 197–198 (description, distribution); Ebert & Compagno, 2007: 116 (listed); Ebert & Davis, 2007: 5–6 (egg case description); Pietsch & Orr, 2015: 17 (listed); Del Moral-Flores et al., 2016 (listed): 110; Last et al., 2016: 25, 390 (figure, listed); Ebert et al., 2017: 21, 58, 67 (description, distribution, key, listed); Burton & Lea, 2019: 32 (listed).

Diagnosis. Small, rounded skates (560 mm TL), disc length and width short (29.0–54.1% TL and 61.2–67.3% TL, respectively), head length short (15.9–21.3% TL), internarial distance short (5.2–6.7% TL); claspers long and thin, tip rounded, not bulbous, pseudosiphon absent, possesses an average pseudorhipidion, not conspicuously projecting from the tip, V-shaped cleft, has a projection and an average sentina, projection is pointed; teeth in 22–31 and 18–31 rows on upper and lower jaw, respectively; pectoral radials 69–72; pelvic fins, 17–22; total vertebrae 132; dorsal surface covered in uniform prickles; thorns present on dorsal surface, males with well-developed alar thorns, malar thorns absent, middorsal thorns range in number (0–9), nuchal thorns strong (3–7), tail thorns few in number (14–22), scapular vary in count (0–2), interdorsal thorns weak or obsolete (0–2), thorns in a continuous row; dorsal coloration mottled brown to grey, possessing numerous small dark spots; ventral coloration white, often with dark brown blotches on underside of tail.

Description. A small skate with a rhomboidal disc, 1.2–2.1 times as broad as long; anterior margin strongly concave in adult males, convex beside and just forward of eyes; apex rounded; posterior margin slightly convex; free rear tip broadly rounded. Disc length and width are smaller than all of its congeners 29.0–54.1% TL and 61.2–67.3% TL, respectively. Head length relatively short 15.9–21.3% TL; preorbital snout length short 9.9–14.0% TL; preoral length 9.0–14.3% TL. Snout tip triangular and rounded; possessing no fleshy process at apex. Eye length moderate 2.3–5.6% TL; a flat to moderately concave area between the eyes; interorbital width short 3.6–5.3% TL. Spiracles average 1.9–3.6% TL, oval shaped; interspiracular space short 5.4–6.8% TL; mouth width short 5.9–8.2% TL. Nasal curtain length average 2.4–3.9% TL, width average 6.2–8.9% TL, its posterior margin fringed at the corners; anterior margin of curtain lobe-like. Internarial distance very short 5.2–6.7% TL; first gill slit length 1.5–2.7% TL; fifth gill slit length 1.1–2.4% TL; distance between first gill slits short 11.6–16.4% TL, and distance between fifth gill slits short 8.0–10.7% TL. Upper jaw moderately well arched, possessing a symphysis; lower jaw convex. Teeth similar in both jaws; teeth unicuspid, with a strong, bluntly pointed posteriorly directed cusp; arranged in longitudinal rows; upper teeth and lower teeth relatively low in number (22–31 and 18–31, respectively).

Pelvic fins small, posterior lobe 8.1–14.9% TL, anterior lobe 7.9–11.8% TL, and inner margin deeply incised 5.5–8.5%. Tail moderate 37.1–62.3% TL, relatively stout; wider at base, tapering to the first dorsal fin origin, not expanded in the middle. Lateral tail fold short 6.2–9.7% TL, similar in both sexes; not obviously broader at any point along its length. Dorsal fins relatively moderate in size and shape, the first dorsal fin taller than second dorsal fin, 2.0–4.0% TL and 1.4–2.9% TL, respectively; bases of both dorsal fins similar in size and length, 2.9–4.9% TL and 2.3–5.3% TL, respectively; anterior margins of both fins concave, apices rounded; free rear tip rounded; interdorsal space average 0.6–3.3% TL, with larger individuals having a shorter interdorsal space, rear tip of first dorsal fin not overlapping base of second dorsal fin. Caudal fin large, low, height 0.6–1.9% TL; its dorsal margin weakly concave; not connected to second dorsal fin by a small membranous ridge. Tail relatively short 37.1–62.3% TL.

Dorsal surface covered in uniform, small, sandpaper-like prickles. Scapular, middorsal, nuchal, interdorsal, and tail thorns present, males with a well-developed set of alar thorns; malar thorns absent; thorns vary slightly in size, from short to well-developed. Middorsal thorns range from absent to high in number (0–9); nuchal thorns welldeveloped and high in numbers (3–7); tail thorns few in number (14–22); scapular thorns absent in some specimens and present in others (0–2); interdorsal thorns weakly developed (0–2). Thorns in a single, continuous row; no multiple rows of thorns on body. Alar thorn patches range between 1–4 rows and 8–22 columns on both pectoral fins.

Mature claspers relatively long and thin, base length 1.3–1.9% TL, inner length 20.6–27.5% TL, tip of clasper rounded and not bulbous ( Figure 21 ). Clasper inner length 28.2–58.0% of tail length; pseudosiphon is absent; inner surface of dorsal lobe with an average pseudorhipidion that does not conspicuously project out from the tip of the clasper; V-shaped cleft; inner surface of ventral lobe possesses a projection and an average sentina; projection is pointed; clasper thin overall.

Clasper skeleton consists of 3 dorsal terminal, 1 accessory terminal, ventral terminal and axial cartilages; dorsal terminal 1 shaped like a long, narrow leaf, and possessing a long shaft; unlike most congeners the dorsal terminal 1 does not form a pseudosiphon externally; the tip of the dorsal marginal is pointed, and forms a long, thin pseudorhipidion externally; ventral terminal curved, possessing a blunt tip that forms the projection externally; accessory terminal 1 nearly as long as the ventral terminal; tip of accessory terminal 1 is pointed; average-sized sentina located above the projection; sentinel present, but fairly small.

Dermal denticles possess 4–5 points on the base of the denticle; moderately developed on posterior third of the dorsal surface; denticles on the first dorsal strongly curved posteriorly and relatively narrow; denticles on head stouter ( Figure 22 ).

Length of rostral cartilage 45.8% of cranial length; prefontanelle rostral length 45.8%; cranial width 78.3%; least interorbital width 18.1%; length of anterior prefontanelle 20.5%; length of posterior prefontanelle 25.3%; length of rostral appendices 18.1%. Rostral cartilage nearly straight; anterior fontanelle spade-shaped; posterior fontanelle gourd-shaped; the posterior fontanelle larger ( Figure 23 ).

Coloration. Dorsal coloration mottled dark brown to brown-grey, with numerous small dark spots on body. Snout semi-translucent; snout and edges of fins sometimes purple. Ventral coloration white, usually with small to large dark brown blotches on underside of tail. Coloration after preservation is similar to fresh specimens; however, the dark spots on dorsal surface tend to become pale in coloration.

Egg case description. Egg cases very small (50–66 mm TL), light to dark brown, dorsal surface covered with fine fibers, ventral surface with either a thin fibrous layer or without. Egg cases possess long, inward bending horns at each corner and strong lateral keels, with the horns flattening and becoming thread-like at the tips ( Ebert & Davis 2007).

Distribution. Bathyraja kincaidii has been confirmed as occurring in the eastern North Pacific, specifically from British Columbia, Canada, south to Baja California, Mexico ( Ebert, 2003). Its range may extend up to Alaska, but confusion with B. interrupta means that the northern extent of its range cannot be verified. It is reported to occur most commonly on the continental shelf-slope break at around 200–500 m, but is possibly found down to 1,372 m at the southern end of its range ( Kyne et al., 2012); however, this study shows an increased depth range of 119–1,050.4 m. Most specimens occurred in the shallow portion of the species range, as there were only three specimens collected at 1,050.4 m; the rest were captured at 119–458.3 m.

Biological notes. Size at maturity for males 44 cm TL; 45 cm TL for females ( Perez-Brazen et al., 2014). Males grow to 62 cm TL; females grow to 58 cm TL. Size at birth is 12–16 cm TL ( Ebert, 2003). Maximum size is at least 62 cm TL ( Perez, 2005; Perez et al., 2011). Maximum age has been estimated to be 17 years for females and 18 years for males ( Perez et al., 2011). Consume invertebrates, notably euphausiids, polychaetes, amphipods, crabs, and mysids ( Ebert, 2003; Rinewalt et al., 2007).

Habitat. Inhabits deep waters, but not as deep as other members of Bathyraja in the ENP ( Kuhnz et al., 2019). Individuals tend to be found in deeper waters at the southern edge of their distribution ( Ebert, 2003). Temperature preferences were observed to be moderate compared to its congeners ( Kuhnz et al., 2019).

Etymology. The species was named in honor of Dr. Trevor Kincaid, University of Washington. Dr. Kincaid collected the holotype specimen.

Comparisons. Bathyraja kincaidii is easily distinguished from most softnose skate species in the ENP. Internarial distance is significantly shorter than all of the conspecifics (F 6,104 = 21.9, p <0.0001). Furthermore, the tail thorn count is significantly lower than all of its congeners (F 6,104 = 24.0, p <0.0001). Bathyraja abyssicola , B. aleutica and B. spinosissima all possess large disc lengths and widths, in addition to obvious color differences. Bathyraja microtrachys , though similar in size, lacks middorsal, nuchal, and scapular thorns. Bathyraja trachura is darkly colored and has much larger dermal denticles on the dorsal surface and a much shorter interdorsal space.

Bathyraja interrupta is very closely related to B. kincaidii and is compared in detail to describe characters that are useful for identification. Besides the morphological traits listed in the prior comparison for B. interrupta , dermal denticles can be used to separate the two species, as B. interrupta has three points on the denticle base and the denticles are posteriorly oriented, with little to no curve along the length. Bathyraja kincaidii possesses four to five points with strongly curved denticles, especially for those on the head region. Some of the best indicators for species identification of softnose skates are the thorn counts. Bathyraja kincaidii has a higher middorsal and nuchal thorn count than B. interrupta (0–9 and 3–7 for B. kincaidii , respectively and 1–8 and 2–5 for B. interrupta , respectively). Bathyraja kincaidii possesses a single, uninterrupted row of thorns down the midline of the dorsal surface. Bathyraja interrupta has an interrupted row of thorns with a noticeable gap between the middorsal and tail thorns.

Remarks. Individuals observed by remotely operated vehicles were found on flat, fine sediment. The species seems to prefer a walking locomotion using its pelvic fins rather than swimming in the water column ( Kuhnz et al., 2019).

Figures

FIGURE 17. Bathyraja kincaidii, PSRC Bkin 020612-1, 575 mm TL, mature male, dorsal view, fresh. Photo by J.D.S. Knuckey. Scale bar = 55 mm.

FIGURE 18. Bathyraja kincaidii, PSRC Bkin 020612-1, 575 mm TL, mature male, ventral view, fresh. Photo by J.D.S. Knuckey. Scale bar = 55 mm.

FIGURE 19. Bathyraja kincaidii, holotype, MCZ 1261, 303.4 mm TL, immature female, dorsal view, preserved. Photo by D.A. Ebert. Scale bar = 55 mm.

FIGURE 20. Bathyraja kincaidii, holotype, MCZ 1261, 303.4 mm TL, immature female, ventral view, preserved. Photo by D.A. Ebert. Scale bar = 55 mm.

FIGURE 21. Components of the clasper for Bathyraja kincaidii, Bkin 020113-1, 591 mm TL, mature male, CL- cleft, PJ- projection, PR- pseudorhipidion, SN- sentina. Photo by J.D.S. Knuckey.

FIGURE 22. Scanning electron microscope images of the dermal denticles of Bathyraja kincaidii, Bkin 020113-1, 591 mm TL, mature male, from A. the first dorsal fin and B. the head region, behind the eyes. Photos by Justin Cordova (MLML).

FIGURE 23. Ventral view X-radiograph of Bathyraja kincaidii, CAS 243648, immature female. X-radiograph by Jon Fong (CAS).