Rhopalodinaria bocherti, Thandar, Ahmed S., Zettler, Michael L. & Arumugam, Preyan, 2010

Thandar, Ahmed S., Zettler, Michael L. & Arumugam, Preyan, 2010, Additions to the sea cucumber fauna of Namibia and Angola, with descriptions of new taxa (Echinodermata: Holothuroidea), Zootaxa 2655, pp. 1-24 : 19-21

Rhopalodinaria bocherti n. sp.

Figures 10, 11 & 12

Diagnosis. A rhopalodinid holothuroid represented by mostly proboscides up to 19 mm long and a juvenile measuring 4 mm. Colour in alcohol off-white. Tentacles 10, eight large, two minute, unbranched. Anus bordered by papillae. Radial plates of calcareous ring with short paired posterior prolongations. Polian vesicle and stone canal single. Ossicles of proboscis comprising tables and plates. Table disc smooth, with spinose four central holes or with one or more smaller holes outside these, spire low to moderate, of four pillars, a single cross-bar, terminating in a ring of unequal teeth, ring sometimes transformed to a cruciform structure or deformed. Plates multilocular, with minute knobs at one end. Tentacle with rods, multilocular plates and rosette-like bodies. Juvenile with only table ossicles with usually, non-perforate crowns. Tube feet of juvenile with curved rods.

Etymology. This species is named after one of its collectors, Dr. Ralf Bochert, to honour him for the painful task he undertook to sort out these valuable collections comprising some very minute individuals.

Material examined. Holotype SAM A28108, AHAB-8, stn. 2, Hole 1, Angola, 18.191° S, 11.841° E, 16.9, 20.v.2004, 32.3 m, Forster & Zettler; Paratypes SAM A28109 , same data as holotype, 2 proboscides; SAM A28110, AHAB-8, stn. 1, Hole 1, Angola, 13.958° S, 12.395° E, 17.11, 20.v.2004, 24 m, Forster & Zettler, 6 proboscides, 1 complete specimen (juvenile).

Description of holotype. Specimen represented by only a proboscis of 19 mm length and 1 mm diameter. Colour in alcohol off-white. Mouth and anus set close together, the latter distinguished by the presence of well developed papillae which can be confounded for the tentacles. Wall of proboscis rigid and slightly rough to the touch. Tentacles retracted, 10, eight large and two very reduced, the latter were originally ventral as they lie furthest away from the anus; all tentacles minute, retracted, rather simple, if any branching exists this is not obvious. Anus bordered by well developed conical papillae, anal teeth absent.

Calcareous ring (Figure 10C) delicate, radial plates anteriorly bifid with short paired posterior prolongations separated by a deep, narrow concavity, mid-ventral radial plate with 3–4 anterior projections; interradial plates smaller, triangular with narrow anterior tip and a concave posterior surface. Polian vesicle short, minute, tubular; stone canal straight, madreporite pyri-form. Retractor muscles as single short strands; longitudinal muscles undivided.

Ossicles of the body wall typically of two types: an outer layer of well developed tables (Figure 10A) and an inner layer of large, multilocular plates (Figure 10B). Table disc (36–60 µm, mean 44.85 µm, SD ± 5.67, n = 20) smooth, circular to oval, with indented margins and only four central holes or with one or more smaller holes situated outside the central holes. Spire low or off moderate height (up to 35 µm), of four pillars, a single cross bar and terminating in a ring of short well developed teeth, unequal length, the latter sometimes reduced to form a cross-shaped structure without apical hole (Figure 10A). Plates (240–388 µm, mean 334.63 µm, SD ± 37.38, n = 16) oval, slightly elongated, multilocular with indented margins and a series of minute knobs at one end of the plate, developing plates knob-less with fewer holes. Tentacle deposits as rods, plates, and rosette-like bodies. Rods ( Figure 11 C) rather large (81–321 µm, mean 161 µm, SD ± 66.53, n = 10), usually perforated once at each end and with spines/tuberosities along margins, other rods ( Figure 11 D) smaller, smooth, with expanded multi-perforate ends, unbranched (37–78 µm, mean 56.35 µm, SD ± 9.02, n = 20) or branched (37–58 µm, mean 48.91 µm, SD ± 6.32, n = 11); tentacle plates ( Figure 11 B) large (> 150 µm), also with uneven margins and many holes and with knobs and spines on surface; rosette-like bodies ( Figure 11 A) of variable form and size (> 30 µm).

Description of paratypes. The two paratypes (13 & 18 mm in length) contained with holotype as well as others (AHAB B1) (7 – 35 mm in length) of similar structure as the holotype; tables of either with nonperforate or perforate spire tops/crowns. Complete juvenile (AHAB B1) (Figure 10D) with sphere of 2.5 mm diameter, proboscis 1.5 mm long, both without plates but only tables with mostly non-perforate spire tops ( Figures 12 A–C), and tube feet deposits as curved rods with 0–2 perforations at each end and short marginal projections/digitations ( Figure 12 D).

Distribution. Type locality (southern Angola), 24– 32 m.

FIGURE 10. Rhopalodinaria bocherti n. sp. Holotype, SAM A28108. A. Tables from body wall; B. body wall plates; C. calcareous ring; D. complete juvenile.

Habitat. Coarse sediments with low organic content.

Remarks. The presence of only 10 tentacles of which two are much reduced and the inclusion of both tables and plates in the body wall, make the new species obviously referable to Rhopalodinaria . It differs from the other two nominal species of the genus in possessing smooth table discs and simple spires in comparison to the clumsy, tables with knobbed discs in both R. gigantea ( Cherbonnier, 1970) and R. minuta ( Cherbonnier, 1970) . Further, the plates of the new species differ in that most possess minute knobs at one end. The absence of plates in the body wall of the juvenile indicates that these deposits develop after the more superficial tables and this may be characteristic of the rhopalodinids.

Figures

FIGURE 11. Rhopalodinaria bocherti n. sp. Holotype, SAM A 28108. A-D. Tentacle deposits.

FIGURE 12. Rhopalodinaria bocherti n. sp. Paratype, SAM A 28110. A. Tables from proboscis; developing tables; C. tables from sphere; D. tube feet deposits.