Ohshimella ehrenbergii Selenka 1868

Ohshimella ehrenbergii (Selenka, 1868)

Figure 6

Urodemas ehrenbergii Selenka, 1868: 14, figs. 6–8.

Phyllophorus n. sp. Semper, 1868: 245, pl. 30, fig. 21.

Phyllophorus ehrenbergi (sic) Lampert, 1885: 181; Théel, 1886a: 151.

Phyllophorus frauenfeldi Ludwig, 1875: 95, fig. 22; H.L. Clark, 1923: 417.

Cucumaria turbinata Pearson (non Hutton, 1878: 307), 1903: 189, pl. 1, figs. 2–6; 1910: 169, text figs. 13, 14; Heding and Panning, 1954, 137, text fig. 59 (synonymy).

Orcula torrense Helfer, 1913: 433, text figs. 1–7.

Urodemella ehrenbergii Deichmann, 1944: 733; 1948: 358.

Ohshimella ehrenbergii Heding and Panning, 1954: 133, text figs. 57–59; Thandar, 1989c: figs. 6b, 8 & 9f.

Ohshimella ehrenbergi (sic) Clark and Rowe, 1971: 182 (dist.), pl. 30, fig. 5; Cherbonnier, 1988: 216, figs. 94 A–J.

? Urodemas gracile Selenka, 1868: 114; Heding and Panning, 1954: 137.

Type

?Gottingberg Museum.

Type locality

Red Sea.

Previous South African records

East coast of KwaZulu­Natal.

Material examined

SAM­A27903, SE of Mission Rocks, Zululand, 28 16.4’ S, 32 31.4’ E, ‘Meiring Naude’, St. ZN 4, R. Kilburn, 10 vi 1988, 30 m, 1 spec; SAM­A27904, off Boteler Point, KwaZulu­Natal, 27 00.4’ S, 32 55.2’ E, NMDP, St. ZB 18 6.vi. 1990, 66 m, 1 spec; SAM A23175, Coconut Bay, Mozambique, 17.v. 1973, 1 spec.

Distribution

Indian Ocean, up to 60 m.

Habitat

Fine sand, rock, stones, coral.

Remarks

All three specimens in the collection are perhaps juvenile of this well­known Indian Ocean species. The depth of the one from Coconut Bay has not been recorded but the other two come from 30 m and 60 m. The smallest individual is in a poor state of preservation (previously dried up), measures 10 mm x 2.5 mm, and is of greyish­brown colouration; the slightly larger specimen is in an excellent state of preservation with the tentacles extended and measures 21 mm x 5 mm and of whitish colouration; the largest measures 34 mm x 12 mm and is of a dull creamish­white colouration. The two smaller specimens show an ambulacral restriction of the podia in 2–3 rows (a juvenile feature), whereas the largest specimen has the podia scattered. In the specimen with extended tentacles there are nine large tentacles in the outer ring and 10 much smaller tentacles arranged in pairs in the inner ring. The calcareous ring is typical of the species (Figure 6 K) with the radial prolongations subdivided.

The body wall spicules comprise the typical spinous rods, measuring 67–81 µm (mean 73 µm) in length in SAM­A27903 (Figure 6 A) and 54–68 µm in length (mean 59 µm) in SAM A23175 (Figure 6 E). In the podia and anal region of the two smallest individuals two types of rudimentary tables are present, both resembling those found in members of the genus Thyone. The first type (Figure 6 C) is similar to that found in the podia of the Thyone species — i.e. with curved discs, 157–181 µm in length (mean 168 µm) in SAM­A27903, with one or two perforations at each end and a two­pillared spire, 62–71 µm high (mean 67 µm), with the pillars uniting at base and ending in paired clusters of teeth. The second type of tables (Figure 6 D) resemble those found in the body wall also of some Thyone species — i.e. with quadrilobed and quadrilocular discs, 81–105 µm long (mean 95 µm), with one or two clusters of teeth. Often the tables are reduced to simple discs with a varying number of holes (Figure 6 B). Endplates present. Podia of larger specimen (SAM A23175) are supported by rods perforated at one or both ends (Figure 6 H), rosette­like rods (64–134 µm, mean 108 µm) (Figure 6 F), multilocular plates (132–210 µm, mean 176 µm) (Figure 6 G) and endplates (ca 350 µm). Rosettes (18–36 µm, mean 24 µm), which characterise the species, only occur in the body wall of the largest specimen. Tentacle spicules (in SAM A 23175) comprise rosettes (Figure 6 J), curved rods of variable length (40–240 µm, mean 99 µm) and thickness (Figure 6 I), the smallest ones with usually a single terminal perforation and/or tuberosities, the larger ones with several perforations at each end as well as rosettes (22–38 µm, mean 29 µm).

This is the first report of rudimentary tables, of the form here illustrated, present in the body wall of this species. These tables differ from those illustrated by Thandar (1989c) from the anal region of his South African material and by Pearson (1910) from his Querimba specimen. Thandar speculated that the anal tables of this species are perhaps juvenile deposits lost with age. It appears that the rudimentary tables of the body wall suffer the same fate. From the material at hand it appears that the rosettes develop after the loss of tables. In fact, Pearson’ s (1903 & 1910) C. turbinata, respectively from Ceylon and Querimba (Mozambique), suspected by Heding & Panning (1954) and Thandar (1989c) to be a synonym of O. ehrenbergii, showed the presence of rosettes in the larger specimen (48 mm) from Querimba and not in the smaller specimen (25 mm) from Ceylon. Incidentally, Pearson’ s Ceylon specimen presumably possessed no tables, as they are not described. Apparently this is a very variable species whose posterior prolongations of the calcareous ring may or may not be fragmented, and its body wall and podial spicules may or may not include tables and/or rosettes, depending on age, depth or geographic location.