Ophiostigma isocanthum (Say, 1825)

Gondim, Anne I., Alonso, Carmen, Dias, Thelma L. P., Manso, Cynthia L. C. & Christoffersen, Martin L., 2013, A taxonomic guide to the brittle-stars (Echinodermata, Ophiuroidea) from the State of Paraiba continental shelf, Northeastern Brazil, ZooKeys 307, pp. 45-96 : 58-59

Ophiostigma isocanthum (Say, 1825) Figure 7 f–l

Description.

Disk circular to pentagonal (dd = 1.58 to 3.31 mm). Covered by small blunt tubercles (Fig. 7f). Some large and blunt tubercles distributed in the interradius, usually near the radial shields. Radial shields small (Fig. 7f, h). Ventral interradius covered by short and blunt tubercles similar to the dorsal ones (Fig. 7g). Bursal slits narrow and long. Oral shields fan-shape (Fig. 7i). Adoral shields united proximally and almost touching the adoral shield of the neighbouring jaw along median arm line (Fig. 7i). Two oral papillae on each side of jaw angle, distal operculate, closing oral slit (Fig. 7i). Dorsal arm plate with proximal margin rounded and distal margin straight (Fig. 7j). Ventral arm plate pentagonal, long. Three conical arm spines (Fig. 7l). Two elongate tentacle scale (Fig. 7l).

Distribution.

Bermuda, North Carolina to Florida and the island off southern Florida, Texas offshore reefs, the Bahamas, the Antilles, Mexican Caribbean, Panama, Colombia and islands off Caribbean, Colombia, Venezuela, and Brazil ( Hendler et al. 1995, Chavarro et al. 2004, Laguarda-Figueras et al. 2004, Durán-Gonzáles et al. 2005, Borrero-Pérez et al. 2008). In Brazil from Pará, Ceará, Paraíba ( Albuquerque 1986), Pernambuco ( Lima and Fernandes 2009), Alagoas ( Albuquerque 1986), Bahia ( Magalhães et al. 2005), and Rio de Janeiro ( Rathbun 1879). Intertidal to 244 m in depth. Recorded from 14 to 34 m in this study.

Remarks.

This species rarely exceeds 7 mm in disk diameter ( H.L. Clark 1933). It lives on rocky bottoms, on or in fine sediment, among shell, corals, calcareous algae, under sponges ( Tommasi 1970, Hendler 1995, Manso et al. 2008), and among the roots of seagrasses ( Thomas 1962). This is a cryptic species that hides by burrowing into the sediment. Individuals with 1mm in disk diameter may already have mature gonads ( Hendler et al. 1995). In specimens having the disc in the process of regenerating, only small granules were observed distributed over the whole disc, the large granules being absent from the inter-radial regions.