Styela meteoris, Monniot, 2002

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 98

STYELA METEORIS SP.NOV. ( Fig. 26 )

Material

Holotype: MNHN S1 STY 274 , Aden, st. 249, 12°29.5¢N–45°38.7¢E, 1299–1314 m, Meteor cruise, 1987.

Description

The ovoid body is 7.5 ¥ 6.5 mm across, its naked dorsal side variably lumpy. The sessile siphons are 4 mm apart; they show four flat lobes. Around the equator of the body is a belt of nonramified rhizoids, 3–4 mm long, without adhering sediment. Just anterior to this belt, the tunic is covered with a thin layer of mud. On the ventral side of the specimen the rhizoids are shorter and fewer. The tunic itself is thin and transparent.

The body wall musculature is made of strong bundles, about 30 ribbons at each siphon. Those located near the cloacal aperture are the most developed. The radiating lateral muscles, coming from both siphons, are thinner and anastomosed. Between the siphons the muscular fibres are not gathered in bundles but rather make a network. There are no transverse fibres on the ventral side of the body.

The oral tentacles are planted at the base of a short velum, very anteriorly in the siphon. Twenty of them in four orders are obviously curved. The prepharyngeal band has two very close equal crests, and forms a dorsal V. The button-shaped dorsal tubercle opens by a straight but oblique slit. The neural ganglion is elongated. The dorsal lamina is long with a plain edge, and progressively increases in height to the oesophagus entrance. The branchial tissue is thin, with three folds on each side, but only the two first ones from the dorsal lamina are well formed. The formula is:

Figures

Figure 26. Styela meteoris sp. nov.: A. specimen ventrally opened. B,C, external view of the left and right sides of the body. D, gonad. Scale bars: A,B,C = 3mm, D = 2mm.