Psolus griffithsi, Thandar, Ahmed S., 2009

Thandar, Ahmed S., 2009, New species and a new record of sea cucumbers from deep waters of the South African temperate region (Echinodermata: Holothuroidea), Zootaxa 2013, pp. 30-42 : 35-41

Psolus griffithsi n. sp.

Figures 5 , 6 & 7

Diagnosis. Holotype 25 mm, sole distinct. Colour beige-grey. Scales imbricating, about ten scales between mouth and anus. Mouth sub-dorsal, oral valves smooth. Tentacles bushy. Anus dorsal, anal valves sub-equal, some accessory valves present. Ventral podia in two rows around sole - outer row of minute podia and an inner row of much larger podia, mid-ventral podia absent except anteriorly and posteriorly. Polian vesicle single. Dorsal scales up to 3 mm, covered with minute granules, easily rubbed off, and baskets arranged in heaps. Baskets mostly flat, 30–80 µm in length (mean 70 µm), with fine knobs. Sole with similar but larger baskets, 60–190 µm (mean 126 µm). Tubefeet and tentacles with smooth perforated plates, end-plates present.

Etymology. The species is named after Prof. Charles Griffiths of the University of Cape Town for passing this unique form onto me for its description.

Material examined. Holotype: SAM –A28046, ‘Nansen 401’, Trawl T003, St. 1289, west coast of South Africa (34° 37.9’S, 18° 18.7’E), 407 m, 11.i.2007, Louise Lange, 1 spec.

Description. Specimen small, 25 mm long, elliptical, broad anteriorly (8 mm), narrower posteriorly (6 mm), length of sole 20 mm. Dorsal surface ( Figure 5 A) well-arched, covered with scales, slightly imbricating, dorsal scales large, lateral scales reduced, about ten scales between mouth and anus. Mouth sub-dorsal, anteriorly directed, bordered by five distinct, large (3 mm), somewhat granular oral valves of more or less equal size, left dorsal one slightly bifurcated. Minute podia often visible between valves. Tentacles well branched, number and size not verified. No accessory valves detected. Anus dorsal, distinct, situated on a slight elevation bordered by five sub-equal valves with about five ill-defined, accessory valves situated within ( Figure 6 E). A few podia present in association with some anal valves. Ventral surface flattened, sole distinct ( Figure 5 B). Dorsal podia absent. Ventral podia in two sharply defined rows bordering sole, outer row of minute podia lying just underneath margin of sole and an inner row of much larger podia with well developed suckers. Mid-ventral podia absent except for a clump of five at the anterior end of sole and a clump of three at posterior end. Dorsal scales with a slightly elevated part showing accumulation of baskets into heaps. Baskets of sole not macroscopic. Colour uniformly beige-grey.

Calcareous ring typical, simple, radial plates slightly longer than interradial plates, anteriorly bifid, each with a deep groove on outer surface for attachment of retractor muscle, interradial plates triangular, posterior margin of ring slightly undulating. Polian vesicle single, situated slightly to left of mid-ventral part of water ring, sac-like. Stone canal short, free. Madreporite delicate, lying in posterior depression of mid-dorsal interradial plate of calcareous ring. Respiratory trees well developed, right one more so, each arising independently from cloaca, both trees with short but well ramified, medial supplementary branch, and a longer lateral branch, terminally ramified. End branches of trees white. Gonad (testis) well developed, with both mature and immature, unbranched tubules in various stages of development, attached anteriorly on dorsal mesentery. Longitudinal muscles unpaired, thin, retractors well developed, arising from longitudinal bands in mid-body, more anteriorly in the mid-ventral ambulacra.

Dorsal body wall encased in a layer of slightly imbricating scales external to which occur minute granules which are easily rubbed off, and a layer of sparse baskets accumulated into heaps, simulating a ‘superstructure’. Scales/plates ( Figure 7 A), up to 3 mm in length, multi-layered, highly complex. Dorsal baskets ( Figure 6 A) minute, scarce, 30–80 µm in length (mean 70 µm, n = 9), with up to 10 holes and up 30 fine knobs on surface, rarely knobs absent, baskets seldom deep and cup-like. Sole deposits also include granules, also easily rubbed off, and baskets, larger that those of dorsal surface ( Figures 6 B, 7B), 60–190 µm (mean 126 µm, SD ± 23.3, n = 20), with up to 13 holes and up to 24 fine knobs; most baskets (± 80%) flat but some with raised margins, giving the baskets the appearance of shallow cups. Buttons absent. Tubefeet with simple, perforated plates 70–200 µm (mean 112 µm, SD ± 37.1, n = 20) of various shapes ( Figures 6 C); endplates apparently made up of several individual plates, each with a fine calcareous mesh-work. Tentacle ossicles ( Figures 6 D, 7C) of two types: one type as few, coarse, delicate plates with large holes; the other type smaller, commoner, less coarse and less delicate, 50–260 µm (mean 106 µm, SD ± 43.8, n = 20) plates with small holes (up to 30). No deposits in gonadal tubules, respiratory trees and retractor muscles.

Distribution. West coast of South Africa, 407 m.

Remarks. From figures of entire specimens of P. ephipiffer Wyville-Thompson, 1846 , provided by Théel (1886) and Carriol & Féral (1985), the present specimen, based on shape and the dorsal position of the anus, appears to resemble this species. However, P. ephipiffer is, according to Carriol & Féral, characterized by unflattened (cup-like) ventral baskets unlike the mostly flat, plate-like baskets of the current material. Flattened ventral baskets are said to occur in P. paradubiosus Carriol & Féral , which is also described as having an external row of small tubefeet and an internal row of larger tubefeet. It is for this reason the specimen was at first thought to represent this species, a viewpoint also expressed by Samyn (pers. comm.). However, it differs from P. paradubiosus , in its smaller size, probable absence of accessory oral plates, accumulation of dorsal baskets into heaps, smaller size of the ventral baskets (up to 250 µm in P. paradubiosus ) and the presence of accessory post-anal plates/scales. Although P. paradubiosus is described as having unequal tubefeet, some material of this species, initially identified as P. dubiosus Ludwig & Heding, 1935 , received from the Muséum national d’Histoire naturelle, Paris, and included with the type material of P. paradubiosus by Carriol & Féral, show two rows of equal tubefeet. In fact, in their comparative table of the four related Psolus species, Carriol & Féral show that all are characterized by equal-sized tubefeet. Further, equal-sized tubefeet are reported for the species by Branch et al. (1993) in material from Marion and Prince Edward Islands, identified by Massin, while O’Loughlin (pers. comm.) states that P. paradubiosus is characterized by two rows of equal-sized tubefeet.. Therefore, one wonders how remarkable is the size difference between the two rows of tubefeet in the type of P. paradubiosus when compared with the type of P griffithsi . Another point to consider is that there is, in most animal groups, a very low relationship between the southern African and the Antarctic-Subantarctic fauna. In fact, as far as our current knowledge goes, South Africa shares no holothuroid species with the Antarctic-Subantarctic region. I am thus certain that the current material is not identical with P. paradubiosus and must be referred to a new species. It is regretted that, despite repeated requests, attempts to obtain the actual type material of P. paradubiosus were unsuccessful. It is therefore imperative that all materials referred to this species be re-examined.

The current specimen was also thought to represent P. antarcticus Philippi, 1857 , based on the description provided by Théel (1886) or P. capensis Ludwig & Heding, 1935 from South Africa. However, P. antarcticus , was originally described as having only five scales between the mouth and anus. In P. capensis , on the other hand, the oral and anal valves and the tentacle deposits are of a different kind. Only three other southern African or Antarctic-Subantarctic species with distinct oral and anal valves and/or rows of unequal tubefeet are P. arnaudi Cherbonnier, 1974 , P. punctatus Ekman, 1925 , and P. granulosus Vaney, 1906 . However, P. arnaudi is a large (75 mm), cylindrical species with pseudobaskets; P. punctatus has lantern-like baskets and spheres dorsally and perforated plates ventrally; whereas P. granulosus has irregular plates dorsally and oval perforated plates with tubercles ventrally, and no anal valves. The remaining Antarctic-Subantarctic species are all characterized by equal-sized marginal tubefeet.

Figures

FIGURE 5. Psolus griffithsi n. sp. Entire. A. Dorsal view; B. ventral view (courtesy Charles Griffiths).

FIGURE 6. Psolus griffithsi n. sp. A. Baskets from dorsal surface; B. baskets from sole; C. minutely knobbed plates from podium; D. smooth plates from tentacle; E. anus with anal and accessory anal plates. E. scale b; rest scale a.

FIGURE 7. Psolus griffithsi n. sp. SE micrograph of A. single dorsal plate; B. baskets from sole; C. plates from tentacle.