Leptasterias tatei, Clark, Roger N. & Jewett, Stephen C., 2015

Clark, Roger N. & Jewett, Stephen C., 2015, A new sea star of the genus Leptasterias (Asteroidea: Asteriidae) from the Aleutian Islands, Zootaxa 3941 (4), pp. 579-584 : 580-583

Leptasterias tatei sp. nov.

Figures 1–11

Type locality. Alaska, Aleutian Islands, Adak Island, Thumb Bay entrance, W side (51° 50.08 N, 176° 32.31 W) (leg. Roger N. Clark, scuba 11 m; 20 July, 2011; R/V Norseman).

Holotype. LACM 2011-158.001

Paratype. LACM 2011-159.001; genetic sample LACM 2011-159.002 Alaska, Aleutian Islands, Amchitka Island, SE side, W of Makarius Bay (51° 23.16 N, 179° 11.02 E).

Diagnosis.Star of moderate size; R to 9 cm, R:r 6–9 ( Fig. 1 ). Five rays, relatively long; abactinal ossicles 2–4 lobed, with single spines; spines relatively short, stout, truncated bearing numerous fine vertical ridges; superomarginal and inferomarginal ossicles bear a single thick, blunt spine, similar to abactinal spines; all spines wreathed with numerous crossed pedicellariae. Tube feet, in four rows. Color in life reddish with lighter mottlings abactinally, actinal surface straw colored.

Description. Moderate sized star R to 9 cm, r = 1 cm, R:r 9.1 (Holotype, Fig. 1 ). Disc small, five rays, fairly long, tapering, relatively soft. Skeleton relatively open; papular areas relatively large, bearing 3–6 papulae, obscured by wreaths of pedicellariae on spines in live individuals; bearing scattered large straight pedicellaria to 1.25 mm long ( Figs. 2–3 ) on papular areas; pedicellariae broadened distally, and bearing four “teeth” per valve. Carinal ossicles 2–4 lobed, bearing single spines, dorsolateral ossicles single spined, also 2–4 lobed, but forming a more open meshwork ( Fig. 4 ), and bearing small, irregular accessory plates; spines relatively short, thick truncated, with strong vertical ridges continuing onto the dorsal surface; encircled by a fleshy wreath of small, crossed pedicellariae up to 0.25 mm in length ( Figs. 4–5 ). Madreporite small, about 3.5 mm in diameter, roughly circular with irregular ridges.

Superomarginal ossicles 4 lobed and inferomarginal ossicles 3–4 lobed ( Fig. 6 ), typically bearing single (rarely two) pedicellariae-wreathed spines, longer and more slender than those of the carinal and dorsolateral series.

Actinal ossicles ( Fig. 6 ) in a single nearly complete series, and bearing a single spine. Adambulacral ossicles ( Figs. 7–8 ) bearing single spines on proximal five, then alternating one and two, (two spines in a vertical series), the proximal spine about ¾ as long and thick as the distal spine; actinal and adambulacral spines with a partial wreath on distal side of variously sized straight pedicellariae 0.25 to 0.75 mm. Oral ossicles narrow, bearing two rather slender spines with partial wreaths of pedicellariae similar to those of the actinal and adambulacral series.

Tube feet in four rows. Color in life: dorsal surface reddish with dark and pale mottlings; spines and madreporite white; oral surface straw colored ( Fig. 9–11 ). Paratype ( Fig. 10 ) agrees with the holotype in all respects, but is smaller, R = 6 cm, r = 1 cm, R:r 6.1 and has somewhat stouter rays.

Distribution. The distribution of L. tatei sp. nov., as well as L. stolacantha ( Fig. 12) is the central Aleutian Islands, Andreanof and Rat Islands (approx. 176° W to 178° E) ( Fig. 13 ). Leptasterias tatei sp. nov. was found at Adak (Holotype, Fig. 1 ; in situ, Fig. 9 ), Amchitka (Paratype, Fig. 10 ), and Hawadax (formerly Rat) (in situ, Fig. 11; not collected) islands. Additional specimens were photographed at Adak as well, but not collected.

Habitat. Found on cobble, boulder and bedrock substrate encrusted with the coralline algae Clathromorphum nereostratum , at depths of 8–16 m, and temperatures of 3.8° to 5.0°C.

Etymology. The name honors Mr. Paul Tate. For more than 40 years he worked throughout the Aleutian Islands, first as a biologist for the Alaska Department of Fish and Game in Dutch Harbor, later as the Captain of the research vessel Norseman.

Remarks. Leptasterias tatei sp. nov. resembles L. stolacantha Fisher, 1930 ( Fig. 12), but differs in 1) its larger size, 2) having thicker spines, 3) wreaths of fewer and larger crossed pedicellariae, to 0.25 mm in length, and scattered large straight, pedicellariae to 1.25 mm, as opposed to 0.13 mm and 0.37 mm, respectively in L. stolacantha , 4) the superomarginal and inferomarginal ossicles bear single spines in L. tatei sp. nov., as opposed to two (sometimes three) in L. stolacantha . Additionally, the spines of L. stolacantha are slender and needle-like. The color of live L. stolacantha also differs in being uniformly tan or light brown.

Although its thick, truncated abactinal spines and large, straight pedicellariae clearly distinguish Leptasterias tatei sp. nov. from all other Aleutian species, it bears some resemblance to four congeners described by Dyakonov (1950) from the western part of the Okhotsk Sea, chiefly near Sakhalin Island. Leptasterias fisheri Dyakonov, 1929 differs from L.tatei sp. nov. by having the aboral spines arranged in more or less longitudinal rows; L. tatei sp. nov. has random arrangement. Leptasterias tatei sp. nov. is distinguished from Leptasterias hirsuta Dyakonov, 1938 by the truncate tips of the aboral spines, and single spines on the inferomarginals. The spines of L. hirsuta have rounded tips. Also, L. hirsuta has diverse types of straight pedicellariae scattered aborally that are smaller than those of L. tatei sp. nov. Leptasterias tatei sp. nov. differs from Leptasterias orientalis Dyakonov, 1929 in having only a single row of actinal ossicles. Leptasterias orientalis has two rows of actinal ossicles (ventolaterals in Dyakonov), and the spines on the inferomarginals change from one to two at about mid-ray. Also, the aboral spines of L. orientalis are long and very fine (acicular). Leptasterias tatei sp. nov. differs from Leptasterias subarctica Dyakonov, 1938 in having smaller actinal ossicles than inferomarginal ossicles; the actinals of L. subarctica are notably larger than the inferomarginals. Also, L. tatei sp. nov. has profuse wreaths of crossed pedicellaria around the aboral spines; the wreaths of L. subarctica are much sparser.

Figures

FIGURE 13. Map of Aleutian Islands, showing known geographic distributions of Leptasterias tatei sp. nov. (●) and Leptasterias stolacantha Fisher, 1930 (▲).

FIGURES 1 – 6. Leptasterias tatei sp. nov., Holotype, 2011 - 158.001. Fig. 1, whole animal, aboral, Bar = 3.0 cm. Fig. 2, aboral surface, Bar = 3.0 mm. Fig. 3, aboral spines & pedicellariae, Bar = 1.0 mm. Fig. 4, aboral surface cleaned of tissue, showing carinal [C] and dorsolateral [DL] ossicles & spines, Bar = 3.0 mm. Fig. 5, aboral spine with pedicellariae, Bar = 1.0 mm. Fig. 6, marginal area of ray, cleaned of tissue, showing arrangement of ossicles (superomarginal [SM], inferomarginal [IM], actinal [AC], and adambulacral [AD]), Bar = 3.0 mm.

FIGURES 7 – 10. Leptasterias tatei sp. nov., Holotype, 2011 - 158.001. Fig. 7, cleaned adambulacral region (actinal [AC] & adambulacral [AD] spines), Bar = 3.0 mm. Fig. 8, uncleaned adambulacral region, showing wreaths of straight & crossed pedicellariae. Fig. 9, Live, in situ Adak Island, Thumb Bay, 13 m (leg. R. N. Clark, 20 July, 2011), Bar = 8.0 cm. Fig. 10, Paratype, 2011 - 159.001. Oral side, Bar = 4 cm.