Holothuria (Thymiosycia) cf. arenicola Semper, 1868

THANDAR, AHMED S., 2007, Additions to the aspidochirotid, molpadid and apodid holothuroids (Echinodermata: Holothuroidea) from the east coast of southern Africa, with descriptions of new species, Zootaxa 1414 (1), pp. 1-62 : 44-46

Holothuria (Thymiosycia) cf. arenicola Semper, 1868

Figure 20

Holothuria arenicola Semper, 1868:81 , 277, p1.20, pl.30: fig.13, p1.35: fig.4.

Holothuria (Thymiosycia) arenicola Cherbonnier, 1988:82 , fig. 32 (synonymy before 1988), Samyn, 2003:81 (synonymy & records to 2003).

Previous southern African record Mozambique.

Material examined

Mission Rocks, KZN, 12 vii 1968, A.S. Thandar, 1 spec.; Isipingo Beach, KZN, 20 vii 1970, A.S. Thandar, 1 spec. (juvenile); Treasure Beach, Durban, KZN, 2 vii 1974, F.L. Farquharson, 1 spec.; Park Rynie, KZN, 20 iii 1981, K.S. Ganga, 1 spec. (All above materials currently in the Royal Belgium Institute of Natural Sciences , Brussels); Treasure Beach ( KZN), 1 spec., (as H. (T.) conusalba , deposited in the Australian Museum under AM J20197 ) .

Description

Specimens cylindrical, vermiform or cigar-shaped, largest 100 mm. Dorsum in life, mottled greyish white to beige to a mottled greyish brown, always with 8–9 pairs of dark greyish-brown or rust-coloured blotches, decreasing in intensity posteriad, ventrum greyish white to brown, skin around anus sometimes rust-coloured. Podia either in the form of only tubefeet, then papillae restricted to anus, or podia papilliform dorsally and as tubefeet ventrally. Water ring usually situated far behind level of calcareous ring. Cuvierian tubules present. Tables of body wall with smooth, circular to quadrangular disc, 50–70 µm, with four central and four or more smaller marginal holes, a stout spire with single cross-bar, terminating in a squarish crown of 12–15 teeth, some larger table discs with five central and up to 14 smaller marginal holes. Buttons thick, 50–80 µm, nearly always regular with smooth to gently undulating margins and 3–4 (sometimes 6) pairs of holes, and occasionally with two poorly defined central knobs, often difficult to demonstrate. Because of the thickness of buttons and the funnel-like shape of the holes, the latter may appear small or large depending on the focal point of the objective.

Local distribution KZN, South Africa, as far south as Park Rynie.

General distribution H.(T.) arenicola (se) almost circumtropical.

Habitat In sand, under rock ledge or between sandstone slabs.

Remarks

The colour of this species is variable, probably depending to some extent on the immediate habitat. Apart from the normal coloured individuals, rust-coloured specimens were also described by Fisher (1907), Deichmann (1958) and Pawson (1976) and black individuals by Pawson (1976). It is because of this and the form of the spicules the specimens are here tentatively referred to H. arenicola . Although cuvierian tubules are said to be present in H. arenicola, Pearson (1913) reports their absence in his specimen from Sri Lanka. The dimensions of the spicules here given correspond well with those given for the species by Fisher (1907), Pawson (1978) and to some extent Rowe (1969). Amongst the tropical Indo-West Pacific species of Thymiosycia, only H. macroperona and H. strigosa have buttons greater than 65 mm (see Rowe 1969) but in these species the table discs are 65–80 µm with eight marginal holes and the holes of the buttons large. H. (T.) arenicola was first discovered in South Africa by the writer but these records were not published (see Thandar 1971, 1984). Dr Cherbonnier, to whom a specimen was initially sent for confirmation of identification, thought that it represented H. hilla . The writer has since examined H. hilla from both Mauritius and South Africa and is forced to disagree with Dr Cherbonnier. This opinion is supported by Dr Rowe (pers. comm.). The current specimens are so typical of H. (T) arenicola as described by other writers, notably Pearson (1913), Panning (1934), Deichmann (1930, 1958) and Pawson (1976, 1978), that they cannot be referred to another species. Dr Rowe (pers. comm.) is of the opinion that the specimens may represent H. (T.) conusalba Cherbonnier from New Caledonia. I hate to disagree with Dr. Rowe and in this I am supported by Dr Samyn (pers. comm.). In fact, both Dr Samyn and I are of the opinion that these specimens and a few others also collected from the KZN coast by Dr Samyn himself but as yet undescribed, may represent either H.(T.) milloti Cherbonnier, 1988 or a new species. The current material differs from H. milloti in the absence of anal valves, pseudobuttons amongst the body wall spicules and plate-like spicules in the dorsal podia. Recently Drs Samyn and Massin have begun a revision of H. (T.) arenicola complex of species on a world-wide basis and the correct identity of the South African material, now in Belgium, must await the outcome of this or some other revision.

Figures

FIGURE 20. Holothuria (Thymiosycia) cf. arenicola Semper. Treasure Beach. A. Tables from dorsal body wall; B. buttons from dorsal body wall; C. table from ventral body wall (side view); D. buttons from ventral body wall; E. tubefeet rods; F. rods from tentacle stalk; G. part of calcareous ring. (A & E scale a)