Ophionereis porrecta Lyman, 1860

Stöhr, Sabine, 2011, New records and new species of Ophiuroidea (Echinodermata) from Lifou, Loyalty Islands, New Caledonia, Zootaxa 3089, pp. 1-50 : 35-36

Ophionereis porrecta Lyman, 1860

Figure 14 B, 16

Material. Sta. 1411: 1 spm; sta. 1422: 5 spms; sta. 1429: 1 spm; sta. 1446: 2 spms; sta. 1450: 1 spm; sta. 1451: 1 spm; sta. 1453: 1 spm; sta. 1455: 1 spm; sta. 1456: 1 spms; sta. 1461: 5 spms; sta. 1462: 1 spm; sta. 1465: 6 spms (1 used for SEM); sta. 1466: 5 spms; sta. 1467: 4 spms; sta. 1468: 1 spm; sta. 1469: 1 spm.

Description. At 4.5 mm dd, disk covered by small round imbricating scales. Interradially at disk edge larger scales, increasing in size towards radial shields. Small oval radial shields, overlapped and separated by disk scales. Dorsal arm plates trapezoidal, distal edge shorter than proximal edge, 1.5 times as wide as long. Supplementary dorsal arm plates small, half as long as lateral edges of ventral plates. Arm spines three, conical, as long as an arm joint.

Ventral disk covered by small, round imbricating scales. Oral shield spearhead-shaped, as wide as long, madreporite larger, with hydropore at right laterodistal edge. Ventral arm plates slightly axe-shaped, distally little wider than proximally, distal and proximal edge convex, lateral edges concave. Single large oval tentacle scale.

Dental plate with four tooth sockets, both ventral sockets shallow depressions, dorsal ones each with a pair of oval fenestrations, completely perforating the plate, but smaller on the internal side, separated by a septum. Oral plates with smooth ear-shaped abradial muscle attachment area, adradial “hinge” with irregular bars and grooves. Proximal lateral arm plates twice as wide as long, spine articulations u-shaped, internally a large hole near the tentacle pore. Vertebrae zygospondylous, with deep proximal depression and distal projection (keel), dorsal surface depressed. Radial shield elongated triangular, with long inner edge (towards adjacent shield), short distal and long proximal outer edge, proximal half divided by longitudinal incision, distally with weak ball-like condyle.

Remarks. For comparison with O. degeneri a small spm of 4.5 mm dd was selected, incidentally from the same sample. In this sample there also was the smallest O. porrecta of the material, at 3.2 mm dd, and a same size O. degeneri . The size range over all samples was 3.2–10 mm dd, and thus O. porrecta reaches about twice the size of O. degeneri . Ophionereis porrecta can be distinguished from O. degeneri by the large marginal radial dorsal disk scales, the longer, tapered arm spines, the smaller supplementary dorsal arm plates, the convex distal edge of the ventral arm plates and by the oral shield being as wide as long. For further discussion see under O. degeneri . The sympatric occurrence of both species at similar size in the same sample further corroborates their validity as separate species.

Distribution. At Lifou this species was found at depths of 4– 130 m. Its true geographical distribution cannot be determined since it has often been confused with O. degeneri , but it appears to be a common species in the tropical Indo-Pacific. Since more than four times as many (38) specimens of O. porrecta as of O. degeneri were collected at Lifou, it appears to be the more common and more widely distributed species of the two, possibly with wider ecological tolerances or more easily collected.

Figures

FIGURE 14. A, Ophionereis degeneri, dorsal aspect. B, Ophionereis porrecta, dorsal aspect. C, D, Ophiomastix caryophyllata, juvenile; C, dorsal aspect; D, ventral aspect. E, Ophiocoma erinaceus, probably night colouration. Scale bars in millimetre.