Molgula dione, (SAVIGNY, 1816)

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 115

MOLGULA DIONE ( SAVIGNY, 1816) ( Fig. 38 )

Cynthia dione Savigny, 1816: 93 , 153, pl. 7, fig. 1, –

Red Sea. Ctenicella dione: Harant, 1927: 366 , – Suez. Molgula dione: Van Name, 1952: 218 , – Aqaba Gulf. Molgula somaliensis Millar, 1988: 845 , figs 10,30m, –

Somalia.

Material

Yemen, Socotra Island, coll. C. Monniot, 1997. Description

The single specimen collected is spherical, 26 mm in diameter, entirely embedded with sand and broken shells, making the thin tunic brittle. The siphons are short, close to each other, not protruding.

The body wall is thin. The musculature is limited to the siphonal sphincters and to strong but short longitudinal fibres that do not extend beyond the siphonal bases ( Fig. 38A,B ). The thick oral tentacles arise at the base of a velum and have two orders of ramifications. The prepharyngeal band forms a wide and deep dorsal V. The slit in the dorsal tubercule is in shape of a C opening anteriorly, with the end of the left horn curved in and the end of the right horn curved out ( Fig. 38C ).

The short dorsal lamina increases in height posteriorly. The branchial sac has seven folds on each side. The infundibula are constituted of two spiral stigmata wound in opposite ways. The formula on the right side is:

Figures

Figure 38. Molgula dione: A,B, external sides of the body. C, specimen ventrally opened. Scale bars = 1 cm.