Synoicum sphinctorum, Kott, 2006

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234: 200

publication ID 10.1080/00222930600621601

persistent identifier

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scientific name

Synoicum sphinctorum

sp. nov.

Synoicum sphinctorum   sp. nov.

( Figures 4D–F View Figure 4 , 10C View Figure 10 )


Type locality. South Australia (Kangaroo I. between Western River Cove and Snug Cove, ‘‘ The Arches’ ’, on rock wall, 10–14 m, coll. K. Gowlett Holmes, 14 November 2001, holotype SAM E3283 View Materials )   .


The colony is a solid sandy mass, although the sand is crowded only on the surface and is sparse internally. The upper surface has dome-like elevations surrounded by about 10 branchial apertures and with a terminal common cloacal aperture. Broad sandy rounded ridges surround the domes. The branchial apertures are in the groove between the central dome and the marginal rounded ridge. The atrial aperture is on a brown-coloured siphon with a large, rounded muscular atrial lip projecting from the anterior rim of the opening. About three fine-pointed papillae are on the posterior rim of the atrial opening. Distinct sphincter muscles surround the atrial and branchial siphons. Gonads were not detected in the type colony. A small papillum projects from the mid-dorsal line just behind the atrial opening. The zooids are obscured by the sand on the colony. The branchial sac has 18 rows of stigmata with about 20 in each half row. The anus opens level with the seventh row of stigmata. The stomach is relatively small with 12 shallow, internal longitudinal folds, although these are not always seen in smaller zooids. Gonads were not detected, but the posterior abdomen is present with two narrow longitudinal muscles from the thorax extending along it.


Although the zooids and the systems are like those of S. concavitum Kott, 1992a   , the sphincter muscles around the siphons are more conspicuous and the colony has more sand. Synoicum obscurum Kott, 1992a   has different colonies with two or three systems per lobe and only irregular creases (rather than longitudinal folds) in the stomach wall. The larva of the present species is not known.


South African Museum