Botryllus tuberatus, RITTER & FORSYTH, 1917

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 67-68

BOTRYLLUS TUBERATUS RITTER & FORSYTH, 1917

Botryllus tuberatus Ritter & Forsyth, 1917: 461 – California.

Synonymy: see Monniot, 1988: 170, fig. 2D – New Caledonia; Monniot F. & Monniot C., 2001: 313 – Philippines.

Material

Mozambique: Ibo Island, coll. C. Monniot, 1995.

Remarks

This inconspicuous species has only been found on the barrier reef. The small flat colonies have one or a few circular systems less than 1 cm in diameter, with dark green zooids visible through a transparent colourless tunic. This species is frequent on Halimeda .

B. tuberatus occurs in different forms. Ritter & Forsyth (1917) described erect colonies with several lobes, each having a common cloacal cavity. This is this shape that Oka (1927a) described for this species under the name B. communis .

Oka (1928) and Tokioka (1953) described B. primigenus with a lobed form in which some zooids are isolated in the tunic without common cloacal openings.

Kott (1985) and Monniot C et al. (1991, photo p. 206) described flat, deeply coloured colonies.

In Mozambique the flat, green colonies are sometimes assembled in large plates. The green colour has been recorded in the Antilles, Polynesia, New Caledonia, and the Philippines, and we have observed it in Galapagos samples (coll. P. Humann). The zooid anatomy and the sexual cycle are the same in all forms.

SYMPLEGMA BAHRAINI MONNIOT C. & MONNIOT F.,1997 ( Fig. 2 )

Symplegma bahraini Monniot C. & Monniot F., 1997 : fig. 7D–H, pl. 1E,F – Arabian Gulf, Bahrain.

Material

Juan de Nova Island: east side, 20 m, external side of the reef, yellow colonies, coll. P. Laboute, 1993.

Mozambique, Ibo Island, external side of the reef, coll. C. Monniot, 1995.

Description

The colonies were collected on Halimeda . They are slightly different from the type.

There are 12 oral tentacles in three orders of size, instead of 16 in the type, and four of them are clearly larger and planted a little posteriorly from the crest that carries the other tentacles. The prepharyngeal band has a simple blade, thickened dorsally, where the urn-shaped dorsal tubercle opens in a simple hole. The dorsal lamina is smooth, posteriorly clearly directed to the left and of increasing height there.

The branchial sac has 11 stigmata rows on each side and an additional transverse oval perforation on the posterior right side. The second row of stigmata does not reach the dorsal lamina. The four longitudinal vessels form an arch over the first stigmata row and are thickened where they join the dorsal lamina. On the left side, the first two longitudinal vessels join the dorsal lamina at the level of the sixth and eighth transverse vessels. The elongated stigmata lack parastigmatic vessels. The formula on the right is:

Figures

Figure 2. Symplegma bahraini: A, ventral side of a zooid having ovaries and testes well developed. B, internal side of the gut. C, ventral side of a protandric zooid with testes only. Scale bars: A,C = 1 mm, B = 0.5 mm.