Ophiactidae Matsumoto 1915

Family OPHIACTIDAE Matsumoto, 1915

Type taxon. Ophiactis Lütken, 1856.

Diagnosis. Disc with scales, often bearing spines or granules. The lateral oral papillae do not form a continuous series along the jaw. Apical papilla, usually tricuspid. Bursal slits usually broad. The second oral tentacle pore opening within the oral slit. Arm spines short, pointed and erect (Bernasconi & D’Agostino 1971; Bernasconi & D'Agostino 1977; Paterson 1985; Albuquerque 1986; Borges & Amaral 2005).

Comments. Initially, the ophiactids were placed as a subfamily of Amphiuridae, (Matsumoto 1915), but were later recognized as a family. The change was due to a difference in the number of the apical papillae, one in Ophiactidae and two in Amphiuridae. Of the extant ophiuroids, only four species, all belonging to the Ophiactidae, produce hemoglobin containing coelomocytes in their water vascular system: Ophiactis virens (Foettinger 1880; Cuénot 1891), O. simplex (Christensen 1998), O. rudropoda (Ruppert & Fox 1988) and Hemipholis cordifera (Hajduk & Cosgrove 1975; Christensen & Colacino 2000; Christensen et al. 2003). The presence of hemoglobin imparts a bright red color to the tube feet and provides a clear diagnostic character that can rapidly distinguish these species from other co-occurring brittle stars (Christensen et al. 2008). The presence of echinoderm globins and the vertebrate neuroglobin and cytoglobin lineages suggests that the split between neuroglobins and cytoglobins occurred in the deuterostome ancestor shared by echinoderms and vertebrates (Christensen et al. 2015). Ophiactidae may occur on sand and mud bottoms and are often associated with sponges, algae, corals and polychaete colonies (Hendler et al. 1995; Borges & Amaral 2005). This family is comprised of 55 species distributed across two genera (O’Hara et al. 2017), of which six and two, respectively, are recorded in Brazil (Barboza & Borges 2012).