Ecteinascidia rubricollis Sluiter, 1885

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1637-1638

Ecteinascidia rubricollis Sluiter, 1885

(figure 6A, B)

Ecteinascidia rubricollis Sluiter, 1885: 163 ; Beneden, 1887: 33; Kott, 1964: 146; 1985: 96. Styela rubricollis: Sluiter, 1900b: 5 .

Ecteinascidia koumaci Monniot, C., 1987: 28 .

Ecteinascidia styeloides: Monniot, 1997b: 567 .

Ecteinascidia thurstoni: Monniot, 1997b: 567 .

Distribution. New Caledonia, Indonesia, central Queensland, southern Great Barrier Reef, Mozambique.

Description. The species has a well-formed terminal branchial siphon and a similar antero-dorsal atrial siphon each surrounded by circular muscles. Longitudinal muscles are confined to the siphons. The transverse body muscles cross the dorsal surface from just anterior to the atrial siphon and extend posteriorly to half-way down the rectum. These transverse muscles terminate ventrally on each side of the endostyle, passing anterior to the pole of the gut loop on the left. The stomach is oval with spiral ridges. The gut makes a deep double loop, although occasionally, when muscles are relaxed, the primary loop forms an obtuse angle with the vertical rectum. The gonads, in the primary gut loop, consist of a circle of lobed male follicles with a group of ova in the centre of the circle. The male follicles lengthen and become branched and relatively crowded. Kott (1985: figure 40a) shows short transverse muscles confined to the part of the left side but on re-examination of the figured specimen (QM GH2046) the transverse muscles are seen to cover most of both sides from dorsal mid-line to the endostyle from just in front of the atrial siphon to half-way down the rectum. Specimens from Campwin Reef Sarina (AM Y1577; Kott, 1964) have also been re-examined and their identity confirmed.

Remarks. The species differs from E. thurstoni in the antero-dorsal position of the atrial siphon (well removed from the terminal branchial siphon) and its shorter less branched and less crowded male follicles. Both species have spiral ridges on the stomach, and both have transverse muscles crossing the dorsal surface, although the present species has more of these in front of, and fewer behind the atrial siphon than E. thurstoni .

Ecteinascidia styeloides: Monniot, 1997b has spiral gastric ridges characteristic of the present species, with which it is conspecific.

Ecteinascidia styeloides: Monniot and Monniot, 1996 from the Palau Is are specimens of E. garstangi . Ecteinascidia garstangi Sluiter, 1898 (from a wide range in the Indo- West Pacific from Hawaii, Micronesia and Melanesia to Mozambique and Madagascar: see Nishikawa, 1986 for synonymy) has transverse muscles across the dorsum in front of, as well as behind, the atrial siphon (like E. rubricollis ), but it lacks the spiral ridges on the stomach found in the present species. Zooids of the Mediterranean and Atlantic species E. styeloides (Traustedt, 1882) have long siphons, a more regular distribution of shorter, less branched testis follicles which form an arc dorsal to the ovary (rather than surrounding it) and are a distinctive colour, suggesting consistent isolation from the Pacific populations. Ecteinascidia koumaci Monniot, C., 1987 and E. thurstoni Monniot, 1997b , also have transverse muscles crossing the dorsum, a few in front of and more behind, the atrial siphon, spiral grooves in the stomach lining and dorsal languets connected by a membrane. Monniot, C. (1987) observed that E. thurstoni has longer transverse muscles which cover a larger part of the sides of the body than in E. koumaci . However, the latter species was not compared with E. rubricollis , with which it appears to be synonymous, differing only in the degree of gut curvature, which in the examined material demonstrates a range from a deep double loop to a gentle sinuous curve. The present species closely resembles but is half the size of E. maxima Kott, 1985 .