Stichopathes paucispina

Stichopathes paucispina (Brook, 1889)

Fig. 3, 4

Cirrhipathes? paucispina Brook, 1889: 86–87, pl. 12, fig. 6.

Stichopathes paucispina: Opresko & Genin, 1990: 307–310, figs 4–5; Bo & Opresko, 2015: 15.

Type and type locality. BMNH 1873.4.26.1 (holotype): locality unknown.

Material examined. Rio Grande Rise, 30º12’49.68”S, 36º50’9.6”W; Initial depth: 750 m; final depth: 800 m. PROERG/ CPRM. EST.: ERG 165. Date: 11/02/2012.Sampling: Dredge (MNRJ 8586, 1 fragment). Rio Grande Rise, 30º44’4.2”S, 36º44’51”W; Initial depth: 650 m; final depth: 585 m. PROERG/ CPRM. EST.: ERG 185. Date: 09/02/2012. Amostr.: Dredge (CPRM). Alcohol (MNRJ 8578; MNRJ 8591, 2 fragments).

Diagnosis. Corallum unbranched, in ascending irregular spirals. Spines conical, slightly compressed, apex moderately sharp, and covered with small tubercles from the tip down the sides to about 2/5 the distance to base. Polypar spines up to 0.34 mm in height, abpolypar spines up to 0.24 mm (from center of base to apex). Distal edge of spines straight and slightly angled distally or perpendicular to the axial surface. Spines in seven to nine longitudinal rows, with five to six rows (rarely four) in side view; distance between spines in a same row between 0.7 and 1.14 mm. Largest polyps usually 2.3–3.4 mm in transverse diameter; and in a density of 2.5 to 3 per centimeter (adapted from Opresko & Genin, 1990).

Description of Brazilian specimens. Corallum monopodial, unpinnulated, whip-like, axis twisted, forming a spiral (Fig. 3 a–b). Total length of specimens 35–44 cm. Thickness near base 1.3–2.4 mm. Diameter of the first spiral 66.01 mm. Spines on distal end of the stem conical, with tubercles mostly on the upper fourth to third of the spine surface; arranged in three to six rows in side view (Fig. 3 c–d), most common four to five rows. Height of spines 0.1–0.27 mm. Proximal-distal diameter of spines at the base 0.15–0.3 mm, and distance between spines in a same row around 1 mm. Width of tubercles on spines 0.009–0.02 mm. Polyps not traced (tissue lost).

Remarks. Despite the lack of soft tissue, specimens of S. paucispina examined herein have spines identical to the holotype: sharp, tapered, with large tubercles, compared with Stichopathes spiessi Opresko & Genin, 1990, the species most morphologically related to S. paucispina (Opresko & Genin, 1990; Brook, 1889; Bo & Opresko, 2015). The specimens examined differ from the holotype [described by Brook (1889) and redescribed by Opresko & Genin (1990)] in spine height, relatively smaller in our specimen (0.11–0.27 mm and 0.18–0.34 mm in the holotype, respectively). A distinct difference in the size of the abpolypar spines is not always evident in the Brazilian specimens.

Stichopathes paucispina occurs on northeastern Pacific seamounts (Opresko & Genin, 1990). Despite the fact that there are no previous records of the species in the Atlantic, Bo & Opresko (2015) recorded specimens similar to S. paucispina collected in Caribbean, but did not confirm the identification, highlighting the need of a revision of the genus Stichopathes. This genus is represented on northeastern Atlantic seamounts by: Stichopathes abyssicola Roule, 1902; Stichopathes gravieri Molodtsova, 2006; Stichopathes gracilis Gray, 1857 (species with smooth surface or with tiny ornamentation); Stichopathes flagellum Roule, 1902, with spines smaller than those described herein (0.05–0.06 mm in S. flagellum, and 0.1–0.27 mm herein); and Stichopathes dissimilis Roule, 1902, with completely smooth spines (according to drawings of Roule, 1905, p. 132–133) and height between 0.25 and 0.4 mm, bigger than the specimens of S. paucispina.

Distribution. Northeast Pacific Seamounts (Opresko & Genin, 1990) and Southwestern Atlantic, Rio Grande Rise (this work) (Fig. 4); from 585 m (this work) to 1350 m depths (Opresko & Genin, 1990).