Cnemidocarpa concha, Monniot, 2002

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 93-95

CNEMIDOCARPA CONCHA SP. NOV. ( Fig. 22 )

Part of Cnemidocarpa hemprichi: Michaelsen, 1919: 76 , pl. 1, fig. 9.

Material

Syntypes: MNHN S1 CNE 189 , Yemen: Socotra Island, coll. C. Monniot (1997) .

Other material examined: Djibouti, coll. F. Jousseaume & H. Coutière, 1897. Gulf of Suez, coll. R. Ph. Dollfus, 1929.

Description

The largest of nine specimens is 9 cm in length. The body is pear-shaped, the anterior part narrower than the posterior part that contains the digestive tract. The cloacal siphon opens in the middle of the dorsal side. The tunic is very hard, thick, of a brownish red colour, with large longitudinal swellings. There are few epibionts.

In formalin the body wall is pale in colour except for the siphonal rim which is darker. Its tissue is opaque and thick. The oral siphon is short. About 30 oral tentacles are irregularly distributed, in two orders of size.

The prepharyngeal band has two blades, the posterior one higher. The dorsal tubercle is large and occupies a large part of the deep V drawn by the prepharyngeal band. The aperture is convoluted.

The four branchial folds on each side lie well apart from each other. An average of 30 longitudinal vessels were counted on the folds and ten between the folds. Between the folds there are six stigmata per mesh, cut by a parastigmatic vessel. The branchial sac extends posteriorly to the oesophageal opening. The dorsal lamina is a blade of equal height along its length. The endostyle is wide, curved along the posterior part of the branchial sac. Its edges fuse a little before the oesophagus entrance. Then it forms a closed appendix, coiled like a snail, protruding into the cloacal cavity against the oesophagus ( Fig. 22C ).

The gut occupies the posterior quarter of the body, in a double loop ( Fig. 22A ). The stomach is spindlelike, passing evenly into a narrower intestine that remains cylindrical along its whole length. There is no caecum. When the intestine reaches the oesophagus level, it curves in a rather long narrow loop ( Fig. 22A ). The lobed anus is close to the cloacal aperture ( Fig. 22A ).

The gonads are elongated, straight, parallel, and very numerous ( Fig. 22A,B ). Few of them are ramified. The genital openings, at the apex of each gonad, are aligned along a wide curve around the cloacal aperture ( Fig. 22A ). The gonads are included within the opaque internal layer of the body wall.

Numerous endocarps are distributed over the whole internal side of the body wall, both among the gonads and in the gut loop ( Fig. 22A,B ). They are transparent vesicles of irregular shapes.

Remarks

This species differs from all described Cnemidocarpa species by its voluminous snail-like coiled postendostylar appendix. An uncoiled endostylar appendix of equivalent structure occurs in Ciona intestinalis ( MacDonald, 1859; Roule, 1884; Millar, 1953; Hoshino & Tokioka, 1967). This kind of structure has only been mentioned by Michaelsen (1919) in Cnemidocarpa hemprichi Hartmeyer, 1916 . I think that Michaelsen (1919) assembled under this name several similar species. Among them the largest specimens, with numerous radiating gonads, belong to the new species C. concha .

Cnemidocarpa concha differs from C. hemprichi by the large size of its specimens, its very thick body wall, and the convoluted aperture of its dorsal tubercle. The branchial sac, which has many more longitudinal vessels on and between the folds, may be taken to have the same structure, taking in account the larger size of the C. concha specimens. In C. concha the gonads are more numerous than in C. hemprichi , they are in long tubes, and regularly arranged with their genital papillae on a circle.

The geographical distribution of C. concha covers the Red Sea from Suez to Djibouti and extends to Socotra Island.

Etymology

From the Latin, concha = shell, to refer to the snaillike postendostylar appendix of this species.

CNEMIDOCARPA HEMPRICHI HARTMEYER, 1916 ( Fig. 23 )

Cnemidocarpa hemprichi Hartmeyer, 1916: 218 , figs 6,7 – Red Sea.

Not Cnemidocarpa hemprichi: Michaelsen, 1919: 76 ; not Monniot C., 1973: 51, fig. 1 = Cnemidocarpa schumacheri sp. nov.

Cnemidocarpa madagascariensis Hartmeyer, 1916: 222 , figs 8,9 – Madagascar; Vasseur, 1967: 116, pl. 5, figs 41–43 – Mauritius.

Material

Yemen: Socotra Island, 1 specimen, coll. C. Monniot, 1997 .

Description

The specimen measures 3 cm in length. The tunic is thin, soft but resistant, with a wrinkled surface without epibionts. The internal anatomy corresponds exactly to Hartmeyer’s description. The oral tentacles are numerous, in three orders of size. The dorsal tubercle opens in a C-shaped slit ( Fig. 23E ). The dorsal lamina is high with a denticulate edge ( Fig. 23D ). The four folds on each side of the branchial sac are clearly separated. The branchial formula on the right side is:

Figures

Figure 22. Cnemidocarpa concha sp. nov.: A, large specimen ventrally opened, all endocarps not figured. B, detail of the posterior part of the right side with gonads and endocarps. C, oesophagus entrance and postendostylar appendix. Scale bars = 1cm.

Figure 23. Cnemidocarpa hemprichi: A,B external view of the left and right sides of the body. C, internal view of the left side. D, part of the dorsal lamina. E, dorsal tubercle. F, apex of a gonad showing the testis vesicles. Scale bars: A,B,C = 1cm, D = 1mm, E, F = 2mm.