Ophiocoma L. Agassiz, 1836

Stöhr, Sabine, 2024, Taxonomic analysis of the genital plates and associated structures in Ophiuroidea (Echinodermata), European Journal of Taxonomy 933, pp. 1-98 : 35-37

Genus Ophiocoma L. Agassiz, 1836

Fig. 15

Type species

Ophiura echinata Lamarck, 1816 .

Examined species

Ophiocoma echinata , O. erinaceus Müller & Troschel, 1842 , O. schoenleinii Müller & Troschel, 1842 (compared to Breviturma krohi ( Stöhr, Boissin & Hoareau, 2013)) , O. scolopendrina (Lamarck, 1816) , B. dentata (Müller & Troschel, 1842) and B. doederleini (De Loriol, 1899)) .

Oral GP

Flat, open right angle (short L-shaped), one end slightly convex attaching to distal edge of OS, the other concave and attaching to inside of OS, rounded angle outwards. (Only examined in O. scolopendrina .)

Adradial GP

Bar-like long, flat for most of its length, with longitudinal ridge on adradial surface, distal end somewhat thicker, articular structures consist of a lateral bar to which abGP attaches, one large condyle, bordered by a spiral-shaped groove and high stereom edge. A large hole at base of condyle, a bulbous process proximal to condyle on dorsal edge.

Abradial GP

Strongly curved, boomerang-shaped, flat, dorsal edge thickened into ridge abradially, distal end widened, concave with oval depression, articulating just proximal to distal end of adGP. Abradial surface with one to several conspicuous pores near distal edge. Longitudinal groove in abradial surface.

Oral shields

Inner side with two small flat middle spurs, two larger flat laterodistal spurs, and a round centrodistal depression to which oral GPs attach. Madreporite inner side with large round central hole, smaller round distal hole, offset to one side a large oval hydropore, visible externally.

Radial shield

Single low condyle bordered by a short dorso-distal groove.

Remarks

All examined species in the closely related genera Ophiocoma and Breviturma Stöhr, Boissin & Hoareau, 2013 are similar in the observed characteristics, but some variation exists. The radial shields have a thicker condyle and an obvious patch of finer stereom proximal to it in O. erinaceus , O. schoenleini and B. krohi . These are less well expressed and more similar to those of O. scolopendrina in B. doederleini and B. dentata . The oral shield has three lateral spurs in O. erinaceus , and all are more embossed than in O. scolopendrina (not examined in other species). The articular structures on the adGP are more strongly expressed in O. erinaceus and the Breviturma species than in O. scolopendrina .

Figures

Fig. 15. Ophiocomidae Ljungman, 1867, SEM, unless otherwise noted. A–P. Ophiocoma scolopendrina (Lamarck, 1816). A. Genital plates in situ, dorsal view, digital photo. B. Genital plates in situ, distal ends, adradial view, micro-CT.C–D. adGP, abGP and RS articulating, adradial aspect. E. Radial shield, inner aspect. F. adGP, ventro-adradial aspect. G. adGP, abradial aspect. H. adGP, abradial aspect. I. abGP, abradial aspect, arrow connects articular structures. J. abGP, adradial aspect. K. Ventral arms and mouth (arrowheads mark oGP), digital photo. L. Oral shield with oGP attached (arrowheads). M. oGP, abradial aspect. N. oGP, adradial aspect. O. Oral shield, inner aspect. P. Madreporite, inner aspect. Q–U. Ophiocoma erinaceus Müller & Troschel, 1842. Q. Radial shield, inner aspect. R. Oral shield, inner aspect. S. Madreporite, inner aspect. T. adGP, abradial aspect. U. abGP, adradial aspect. Scale bars: A–B, E, K–L, O–P= 0.5 mm; C–D, F–J, Q–U= 1 mm; M–N= 0.1 mm.