Ophiomyxa 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 : 33-35

Genus Ophiomyxa Müller & Troschel, 1840

Fig. 14A–Q

Type species

Ophiura pentagona Lamarck, 1816 .

Examined species

Ophiomyxa pentagona , O. serpentaria Lyman, 1883 .

Oral GP

Elongated, three and a half times as long as greatest width, bar-like, flat, proximal end thickened, straight edge.

Adradial GP

Bar-like, proximal half flat, distal half thicker, end round, curving dorsalwards to meet RS, distal edge flat. In middle of ventral edge, a short process, to which abGP attaches.

Abradial GP

About half as long as adGP, flat, thin blade, straight, distal end slightly thicker, dorsalwards curved, edge slanting, proximal end rounded. Adradial surface in distal part with one to several conspicuous pores.

Oral shields

Rounded triangular, distal edge convex and thicker than thin main part. Madreporite distally inflated, inner side with large distal opening, a spur to either side, smaller hole in one laterodistal edge.

Radial shield

Rectangular to bar-like, distal end wider than proximal end, on distal inner side a patch of denser stereom as articular structure, no condyle.

Remarks

The abGP of Ophiarachna incrassata (Lamarck, 1816) ( Fig. 14S ) somewhat resembles the hockey-stick shape of the abGP of Ophiochiton ( Fig. 24C ) or a longer version of the abGP of Ophioderma ( Fig. 13F ). Its adGP ( Fig. 14R ) has a condyle and a condylar process (or two condyles), unlike that of Ophiomyxa , but resembling that of Ophioderma ( Fig. 13E, G–H ). No material was available to examine other angles of O. incrassata (nor any other congeneric species).

Figures

Fig. 14. Ophiomyxidae Ljungman, 1867, SEM, unless otherwise noted. A–K. Ophiomyxa serpentaria Lyman, 1883. A–C. Digital photos. A. Arm, dorsal view. B. Arm and mouth section. C. Arm and mouth section with oral shield removed. D. Arm with genital plates attached. E. adGP, adradial aspect. F. adGP, abradio-ventral aspect. G. abGP, arrow connects articular structures. H. Madreporite, inner aspect. I. Oral shield, inner aspect. J. oGPs. K. Radial shield, inner aspect. L–Q. Ophiomyxa pentagona (Lamarck, 1816).L. oGPs, view from inside disc, micro-CT.M. adGP, adradial aspect.N. adGP, abradial aspect. O. abGP, arrow connects articular structures. P. Radial shield, inner aspect. Q. Madreporite, inner aspect. R–S. Ophiarachna incrassata (Lamarck, 1816). R. adGP, abradial aspect. S. abGP. Scale bars: A–Q =0.5 mm; R–S =1 mm.

Fig. 24. Ophionereididae Ljungman, 1867, SEM, unless otherwise noted. A–C. Ophiochiton fastigatus Lyman, 1878. A. Ventral disc section, digital photo. B. adGP, proximal end broken. C. abGP. D–J. Ophioplax lamellosa Matsumoto, 1915. D. Ventral interradius. E. adGP, lateral aspect (adradial?). F. abGP. G. adGP, dorsal aspect. H. Radial shield, inner aspect. I. Madreporite, inner aspect. J. Oral shield, inner aspect. Scale bars: 0.5 mm.

Fig. 13. Ophiodermatidae, Ljungman, 1867, Ophioderma longicaudum (Bruzelius, 1805), SEM, unless otherwise noted. A–C. adGP and abGP in situ, in various orientations, micro-CT. D. adGP and abGP in situ. E. adGP, abradial aspect. F. abGP, arrow points to corresponding articular structure on adGP. G. adGP, adradial aspect. H. adGP, dorsal view. I–J. adGP, distal aspect. K. Radial shield, inner side. L. Oral shield, inner side. M. Jaw (arrowhead marks oGP), bleached, digital photo. N. Jaw with oral shield removed, oGP exposed (arrowheads), bleached, digital photo. O. Pair of oGP, ventral aspect. P. oGP, lateral aspect. Q. Madreporite, inner side. Scale bars: 0.5 mm.