Leptychaster kerguelenensis Smith 1876

Romanelli, Mariela V. & Tablado, Alejandro, 2011, Leptychaster kerguelenensis (Echinodermata: Asteroidea) from Southwest Atlantic: Redescription and geographic distribution, Zootaxa 2971, pp. 59-68 : 64-66

Leptychaster kerguelenensis Smith 1876

Figures 3 and 4

Leptychaster kerguelenensis Smith 1876 , p. 110

Leptoptychaster kerguelenensis: Smith 1879 , p. 278, pl. 17, fig. 2 Leptoptychaster kerguelensis: Koehler 1917 , p. 52, pl. 6, figs. 1, 2, 7, 12 Leptoptychaster mendosus Koehler 1923 , p. 98, pl. 12, figs. 3–5 Leptychaster kerguelenensis mendosus: Fisher 1940 , p. 84.

Compressed disc; rays five (R:r from 2.0–5.0); width of arms do not decreases along them but it do rapidly at distal end, ending as blunt point; madreporite obscured by abactinal paxillae ( Fig.3 ).

Abactinal plates paxilliform, arranged irregularly, projecting proximal edges of plates lobed, reduced in size to the center of the disk and toward the midline of arms (near superomarginal plates from 2.3–2.7 mm size, carry 15– 33 spines from 0.1–0.2 mm long; center of disk and arms from 1.8–2.0 mm size, carry 15–24 spines from 0.1–0.2 mm long) ( Fig. 4a and b).

Superomarginal plates paxilliform, similar but larger than abactinals (from 2.9–3.2 mm size, carry 20–32 spines 0.1–0.2 mm long), and separates from inferomarginal ones by a well-defined groove ( Fig. 4 c). Inferomarginal plates tall, short, forming vertical edge of body; with prominent metapaxillar ridge raised transversally to the ambulacral groove (from 1.2–1.7 mm tall and from 0.3–0.5 mm wide) in middle of the ray, carry on top of the ridge 43–61 spines, 0.2–0.3 mm long, arranged irregularly ( Fig. 4 e). Slope of ridge carry small, thin and delicate hairlike spinules, parallel to base plate, and interlaced spinules forms fasciolar grooves between contiguous inferomarginal plates ( Fig. 4 f).

Small triangular actinal area with small paxilliform plates, arranged in a few rows from the mouth to distal end of arm (from 0.7–0.8 mm size, carry 12–22 spines 0.3–0.4 mm long). Only one row of actinal plates is present between furrow and margin in the most part of the arm ( Fig. 4 g). Adambulacral plates are widely spaced, consecutive plates being united by broad ligamentous bands. Each plate carry 6–10 spines, 2 furrow spines (from 1.3–1.4 mm long) and 4–8 subadambulacrals spines (from 0.9–1.2 mm long) ( Fig. 4 d). Oral plates elongate (from 2.9–3.3 mm long and 0.4–0.5 mm wide), 6–9 oral spines in each oral plate and 10–20 suboral spines (the oral ones are longer than the suboral) ( Fig. 4 h).

Distribution. Southern Indian Ocean platform (Subantarctic convergence) surrounding the Kerguelen and Marion islands, 55–182 m depth; Southwestern Atlantic platform between 48° to 55° S; from 86–152.5 m depth ( Fig. 5 ).

Remarks. The above redescription is based on previous descriptions ( Sladen 1889, Koehler 1923) and the study of MACN-In specimens, with sizes ranging R from 12–66 mm and r from 2–16 mm.

Figures

FIGURE 3. General view of Leptychaster kerguelenensis. a) MACN-In 29724 from Southwester Atlantic. b) Drawing of a Keguelen´s specimen by Sladen (1889). c) MACN-In 37920 from Kerguelen Is., aboral view. d) Idem before, oral view. Scale bars length = 1 cm.

FIGURE 5. Known (shadow) and possible (horizontal lines) geographic distribution of Leptychaster kerguelenensis. Square: Type locality of Leptychaster mendosus. Triangle: Locality of the specimen studied by Fisher (1940). Circle: Shinkai Maru stations. Dotted line: Antarctic Convergence.

FIGURE 4. a) Abactinal plates top view. b) Abactinal plates lateral view. c) Superomarginal plates, second line from the bottom, just over the inferomarginal plates. d) Adambulacral plates. e) Inferomarginal plates. f) Detail of hairlike spinules on inferomarginal plates. g) Actinal plates. h) Oral plates. Scale bars = 1 mm.