Amphicarpa prolifera, (SLUITER, 1905)

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 73-74

AMPHICARPA PROLIFERA ( SLUITER, 1905) ( Fig. 7 )

Stolonica prolifera Sluiter, 1905: 12 , pl. II,5 – Djibouti; Obok.

Material

Mozambique: Ibo Island, south of Matemo, external reef slope and cliff, coll. C. Monniot, 1995.

Djibouti: Musha Island, 3–15 m, coll. C. Monniot, 1996.

Suez Gulf: Raz el Kanisa, 3 m, coll . Tel Aviv University.

Description

Amphicarpa prolifera is a species that is difficult to recognize amongst the other small Styelidae covered with sand. It makes little colonies of a few zooids 2– 4 mm in height, linked by stolons. This species often grows on other ascidians or mixed with Amphicarpa inhacae . This habit may cause some confusion with young specimens.

The body wall is thick, deeply pigmented in brown, and has a strong musculature. There are about 30 curved oral tentacles, in two or three orders of size with their bases joined. The prepharyngeal band is a single blade that makes a dorsal V. The dorsal tubercle is protruding and opens in a longitudinal slit. The neural gland extends beyond the round neural ganglion on each side.

The dorsal lamina is high. The branchial sac has two or four folds on each side. When the branchial sac has four folds on each side, folds no. 2 and 4 are thinner and lower and disappear posteriorly. There are generally six tightly arranged longitudinal vessels on folds 1 and 3 but only one or even no vessels between the folds. Parastigmatic vessels are present everywhere. There are about 15 rows of stigmata.

The gut ( Fig. 7A–C ) forms a very short loop. The wide, short stomach has a dozen ridges that become shorter near the typhlosole. The finger-like caecum is short. The intestine is wide and short, the anus simple.

There is a row of gonads on each side ( Fig. 7A–C ). On the right side it is close to and parallel to the endostyle. On the left side and anteriorly, it is close to the endostyle, and more posteriorly on the left it makes a loop above the gut ( Fig. 7A,C ). The polycarps all have a pyriform male lobe ending in a small sperm duct that protrudes into the cloacal cavity ( Fig. 7D ). Only some polycarps, either on the right or on the left side, have an ovary ( Fig. 7A–C ) as well, which contains a large oocyte sometimes lying beside a smaller oocyte. The ovary is located on the internal and posterior side of the testis ( Fig. 7D ). The oviducts have not been found, they may appear by a rupture of the ovarian envelope. The most anterior polycarps have the largest oocytes.

Some large endocarps are scattered on the body wall. The base of the cloacal siphon is circled by a row of thin tentacles.

The larvae ( Fig. 7E ) are large, and generally only one is well developed at a time. The trunk is 1 mm long. The three adhesive papillae are set well apart. The sensory organ lies in the posterior third of the trunk.

Remarks

Sluiter’s species is re-collected for the first time. It has been compared to the type colony held in the MNHN, no. S1 STO 14, and corresponds on all points. Sluiter’s description corresponds well to the type colony .

By size, the zooids’s disposition, the way the tunic is covered with sediment, and the body wall’s pigmentation, this species is very close to A. inhacae ( Millar, 1956) . It differs in the structure of its polycarps and the number of longitudinal branchial vessels.

Figures

Figure 7. Amphicarpa prolifera: A, specimen from Djibouti: ventrally opened. B, C, small specimens from Mozambique. D, two polycarps. E, larva. Scale bars: A,B,C = 2 mm, D = 0.5mm, E = 1 mm.