Stomozoa roseola Millar, 1955

Monniot, Françoise, 2016, Ascidians (Tunicata) of the French Guiana Expedition, Zootaxa 4114 (3), pp. 201-245 : 215-216

Stomozoa roseola Millar, 1955

Figure10 .

Stations. CP4357; CP4399.

In single or fused lobes the colonies are 4 to 6cm large, hard, cartilaginous and opaque. The surface is convoluted with spaced holes of the siphon apertures. The narrowed but thick basal part wears some epibionts. One colony remains pink in formalin with brown siphonal apertures ( Fig. 10 A). The zooids are difficult to remove from the dense tunic. The largest are 17mm long of which the thorax is 6mm. The posterior vascular processes are long. Both siphons have 6 fringed lobes, the oral one apical and the atrial at a short distance below. Both have an internal velum. There are numerous oral tentacles. The longitudinal muscles issued from each siphon run obliquely over the thorax and extend in 2 bundles along the whole abdominal length. Transverse muscular fibres are dense on the whole thoracic wall. The pre-pharyngeal band in a single rod is not indented dorsally. The button-like dorsal tubercle opens in a vertical slit. The rapheal languets are long and thin. The branchial sac ( Fig. 10 B) contains 24 to 26 stigmatal rows the posterior ones sometimes not complete. There are no longitudinal vessels. The digestive loop is straight. The olive-shaped stomach with a smooth wall is separated from the tubular intestine by a constriction. The male and female gonads are located inside the gut loop behind the stomach. A long sperm duct follows the rectum. No larvae were found. No spicules have been detected in the tunic.

Millar (1955) described for the first time Clavelina roseola from South Africa adding in Millar,1962 additional characters depicted from newly collected material. In his later publication (1962) he stated that Stomozoa murrayi Kott, 1957 became a synonym of his species but did not recognize the genus Stomozoa . Surprisingly Millar (1977) identified as Stomozoa murrayi specimens collected from the Brazilian coast down to 60m depth. After his description the characters are the same as in S. roseola except the presence of atypic spicules in the tunic.

Millar (1977) suggested that the specimens tentatively named Diazona gigantea ? by Monniot C. & F. (1969 – 1970) from northern Brazil correspond to S. roseola but they belong to the genus Diazona having longitudinal vessels.

Material from New Caledonia named S. murrayi in Monniot F. (1988) , specimens from Indonesia named S.

roseola in Monniot F. & C. (1996) and material from the south of Madagascar ( Monniot F. 2012) all correspond in all characters to S. roseola ( Millar 1955) , S. murrayi Kott,1957 being a junior synonym to this species.

Both Australian species S. australensis Kott, 1990 and S. bellissima Kott, 1990 differ by a branchial sac with far fewer stigmatal rows.

Figures

FIGURE 10. Stomozoa roseola. A, colony in formalin; B, branchial sac. Scale bar = 2.5 mm.