Ophiothrix Müller & Troschel, 1840

Stöhr, Sabine, 2024, Taxonomic analysis of the genital plates and associated structures in Ophiuroidea (Echinodermata), European Journal of Taxonomy 933, pp. 1-98 : 60-62

Genus Ophiothrix Müller & Troschel, 1840

Fig. 29

Type species

Asterias fragilis Abildgaard in O.F. Müller, 1789.

Examined species

Ophiothrix fragilis .

Oral GP

Oval scale-like, thin, as long as OS, some with notch in proximal part of ventral edge. Pair at acute angle, to either side of distal lobe on OS, half covered by OS. Visible through skin as v-shaped pair of ossicles, supporting proximal end of genital slits.

Adradial GP

Bar-like with bulbous distal end, curved with dorsal edge concave, ventral edge convex. Slanting away from arm, not completely vertical. Large, round, knob-like condyle at distal end bordered by deep groove meets similar condyle on underside of radial shield. Proximal to condyle several other protrusions and fine meshed stereom patches.

Abradial GP

Half-circle to kidney-shaped, dorsal edge concave in middle, straight in proximal half, dorso-distal end with concave articular groove, ventral edge strongly convex. Articulated with adradial GP by elongated depression. Almost dorsoventrally horizontal, only slightly downward slanting. Dorsal surface with radiating striations, ventral surface without.

Oral shields

Oral shield with distal lobe, to which at either side an oral GP attaches. Madreporite bulging in centre, with large central opening.

Radial shield

Large distal condyle, bordered by curved groove, proximal to condyle a kidney-shaped patch of smooth, finer meshed stereom.

Remarks

In Ophiothrix , the oral GP are more obvious than in most other here examined genera, strong and large plates, in contrast to the small, thin scales covering the soft ventral disc.

Figures

Fig. 29. Ophiotrichidae Ljungman, 1867, Ophiothrix fragilis (Abildgaard in O.F. Müller, 1789), SEM, unless otherwise noted. A. Genital plates and radial shield inside disc, micro-CT. B. Genital plates in situ, ventral aspect. C. adGP, abradial aspect. D. adGP, adradial aspect. E. abGP, abradial aspect. F. abGP, adradial aspect. G. Radial shield, internal aspect. H. Madreporite, internal aspect. I. Oral shield, internal aspect. J. oGP (arrowheads) in situ, ventral aspect, digital image. K. Same, internal dorsal aspect. L. oGP. Scale bars: A–G, J–K =1 mm; H–I, L=0.5 mm.