Ophiopristis gadensis, Rodrigues, Clara F., Paterson, Gordon L. J., Cabrinovic, Andrew & Cunha, Marina R., 2011

Rodrigues, Clara F., Paterson, Gordon L. J., Cabrinovic, Andrew & Cunha, Marina R., 2011, Deep-sea ophiuroids (Echinodermata: Ophiuroidea: Ophiurida) from the Gulf of Cadiz (NE Atlantic), Zootaxa 2754, pp. 1-26 : 8-11

Ophiopristis gadensis sp. nov.

( Figs. 3–5 )

Material examined. Holotype: NE Atlantic: Gulf of Cadiz, Captain Arutyunov MV, MSM01-03, stn 195, 1 ind. (NHM 2010.352 Holotype).

Paratypes: same data as holotype, 12 inds. ( DBUA 001147.01); 7 inds. (NHM 2010.353-359).

Diagnosis. Ophiacanthid with sub-pentagonal disk; radial shields exposed, triangular in shape and less than a half disk radius in length; disk covered by thin plates; some plates bearing a spinelet; spinelets long, hollow with a smooth tip or 2–3 pointed spires.

Oral surface covered with thin opaque skin in larger individuals but skin not obvious in smaller specimens; two apical papillae with 3 to 5 pointed oral papillae; second oral tentacle pore emerges superficially onto the oral surface, 3 to 5 rounded tentacle scales associated with pore; adoral shield separating oral shield from first lateral arm plate; oral shield triangular to sub-pentagonal.

Arms distinctly noded at least 4 times disk diameter; plates become glassy on distal segments; dorsal arm plates triangular to scallop-shaped, proximally contiguous in large specimens, separated in smaller individuals; ventral arm plates rectangular with a convex distal edge; lateral arm plates with six arm spines; arm spines up to three arm segments long, dorsal arm spines finely rugose round to slightly flattened, ventral arm spines more obviously flattened with saw-like edge; proximal tentacle pores armed with two to three sub-equal tentacle scales, further out on the arm the scales reduce to two, one large leaf-like scale partially overlying a smaller scale.

Holotype description. disk sub-pentagonal (d.d. 8.3 mm). Arms at least four times disk diameter. Disk covered with thin scales, many carrying a spinelet. Spinelets long, hollow, rugose, with tip of spinelet produced into a smooth point, sometimes with two or three small pointed spires; spinelets in middle of disk finer than those on the periphery or in the interbrachial region. Radial shields exposed, approximately triangular in shape; each shield pair separated along whole length; length extending slightly shorter than a quarter of the disk diameter. Ventral interbrachial area covered with small scales. Spinelets present but shorter and with a lower density than aboral surface.

Oral surface covered by thin skin, partially obscuring the plate beneath. Jaws slightly longer than broad. Two apical papillae on most jaws. Up to five oral papillae along each jaw edge, papillae longer than wide with pointed tip; small pointed, distal papillae lie deeper within mouth. Second oral tentacle pore emerging superficially onto the surface of the jaw. Oral tentacle scales larger than oral papillae, four to five in number, often longer than high with a rounded free edge; tentacles scales superficial situated on oral surface and separated from oral papillae. Adoral shields large, slightly wider at their junction with the arm plates and separating oral shields from first lateral arm plate. Oral shields rounded pentagonal slightly longer than broad.

Arms long, distinctly noded in proximal segments, arm plates becoming glassy. Disk plates extending onto proximal arm segments nearly surrounding first dorsal arm plate. Dorsal arm plates triangular to scallop-shaped with convex distal edge; plates contiguous at least on proximal segments; on distal segments dorsal arm plates more triangular and just contiguous. Ventral arm plates approximately rectangular with a convex distal edge, contiguous on proximal arm segments. Tentacle pores covered, on the proximal segments oval scales, slightly pointed and often of different sizes; each pore with three scales arranged around the first two to four arm pores, decreasing to two thereafter until nearly the end of the arm; two scales comprised of a large glassy, slightly pointed, almost leaf-like scale sitting over a smaller inner scale. Lateral arm plates flared forming a ridge along the area where arm spines inserted. Arm spines six, up to three arm segments in length on proximal arm segments becoming shorter on distal ones; not quite forming a continuous row on the first free arm segment. Dorsalmost spines finely rugose, slightly flattened; ventralmost spines shorter, wider at the base of the spine, much flatter developing a saw-like edge with distinct teeth, terminating in triple-tipped spine; tip of arm spine glassy. These ventralmost spines become shorter on outer arm segments forming a row of large teeth along the ventral edge on the outer part of the arm spine.

Variation (Paratypes). Large individuals conform to the description of the holotype. Smaller individuals, d.d. 3.5 to 6 mm, do not have thickened skin over the oral surface so the plates are clearer. Oral shields are more rounded slightly wider than long. Jaws with three to four oral papillae which are slightly more rugose than in larger specimens. However in other characters, such as tentacle scale number and arrangement, smaller specimens resemble the larger, although the gap between the oral papillae and oral tentacle scales is more obvious. Oral shields triangular slightly more elongated and rounded. Dorsal arm plates on smaller specimens are triangular with a convex distal edge and are separated, not contiguous. Often just two tentacle scales The number of scales may be the result of a larger scale being split perhaps during development thus resulting in three scales not two.

Distribution and ecology. This species is only known from the type locality. It was collected from a coral thicket ( Dendrophylia cf. alternata , mostly dead branches with a few living polyps) at a single station on the flanks of Captain Arutyunov MV at a depth of 1390 m, together with Ophiactis abyssicola , Ophiacantha aristata and Amphioplus hexabrachiatus .

Etymology. This species is named after the area (Gulf of Cadiz) where it was first discovered; Gades is the old Roman name for Cadiz.

Remarks. Placing this species within Ophiopristis Verrill, 1899 represents a compromise and potentially expands the definition of the genus. There are a number of characters which appear to be unique. The emergent radial shields are unusual in the Ophiotominae and in Ophiopristis , the arrangement of the oral papillae and second oral tentacle scales are also distinct and finally the development of thickened integument has not been reported within species of the genus. However, such variation in the degree of skin covering the disk has also been noted for other ophiacanthids, for example Ophiolebes scorteus Lyman, 1878 , without resorting to the erection of a new genus. It is possible that this combination of characters within this species represents a new genus, however as Paterson (1985) and O’Hara and Stöhr (2006) point out, the genera within Ophiacanthidae are not well defined and so adding another would only serve to add to this problem. Ophiopristis gadensis sp. nov. share the following features with other species of the genus - the arm spines are slightly flattened with a rugose edge, the oral and second tentacle papillae are separated either physically or by shape and size, the tentacle scales are multiple in proximal arm segments. Ophiopristis can now be defined as: jaws longer than broad, flanked on each side by four or more oral papillae, second oral tentacle pore superficial opening near the surface of the jaw, armed with tentacle scales similar in size and shape to the oral papillae, sometimes confluent with oral papillae but in some separated; adoral shields long and narrow, separating the oral shield from the first lateral arm plate; disk covered with small scales carrying an elongated spinelet, often long, hollow and with pointed or furcate tips; radial shield usually concealed but maybe exposed; arm spines flattened, carrying a row of sharp points along each edge; tentacle pores armed with up to four tentacle scales on proximal first two to four pores decreasing to one to two large scales on segments thereafter.

According to Stöhr and O’Hara (2007) there are eight species of Ophiopristis . O. gadensis sp. nov. differs in the type of disk spines which are more rugose and not smooth as in most of the other species; the presence in larger specimens of the thickened integument and the distinct separation between the oral papillae and the second oral tentacle scales. Ophiopristis gadensis sp. nov. is similar to O. dissidens Koehler, 1905 in having three tentacle scales on proximal tentacle pores but differs in that the disk spinelets are not smooth, glassy and hollow. A comparison of the species is given in Table 2.

Figures

FIGURE 3. Ophiopristis gadensis sp. nov. A – B: Holotype, C – D: smaller specimen (paratype). A, D: ventral aspect; B, C: dorsal aspect. Scale bars = 1 cm.

FIGURE 4. Ophiopristis gadensis sp. nov. (Paratype). A – B: ventral aspect, C: jaw detail, D: dorsal aspect; E – F: dorsal radial shield; G: disk spinelets; H: arm ventrally; I: arm ventrally and tentacle scale; J: outer arm ventrally; K: arm dorsally spines; L: detail of arm dorsally and spines. AS, adoral shield; DAP, dorsal arm plate; LAP, lateral arm plate; OP, oral papillae; OS, oral shield; S, spinelet; TS, tentacle scale; VAP, ventral arm plate.

FIGURE 5. Ophiopristis gadensis sp. nov. A – B: ventral view of adult (disk diameter: 9.5 mm), b) oral frame of juvenile specimen (disk diameter: 3.5 mm), c) disk spinelets, d) ventralmost spine from distal arm segment, e) mid arm spine f) arm dorsally spine. Bar scales = 1 mm.