Synoicum sacculum Kott, 1992

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 199-200

Synoicum sacculum Kott, 1992

( Figure 10A, B )

Synoicum sacculum Kott 1992a, p 499 and synonymy.

Distribution

Previously recorded (see Kott 1992a): South Australia (Great Australian Bight, Gulf St Vincent, West I., Thorny Passage); Victoria (Flinders); Tasmania (W. Granville Harbour). New records: South Australia (Kangaroo I., Vivonne Bay , 2–3 m, SAM E2864 ; ‘‘The Arches’’ , 10–12 m, E3288 ).

Description

The colonies consist of irregular sandy cushions to 3 cm diameter or lobes up to 1 cm high and 0.5 cm diameter. The lobes are concave on the upper surface. Basally they are attached to a common basal mat. Sand is present on and in the test and is absent only from around the thoraces at the top of each lobe. The especially small (4 mm long) zooids, obscured by sand, are arranged in two or three circular systems (each of up to 10 zooids) per lobe. The common cloacal openings can be seen only when the sand is removed from the delicate test. Zooids have the usual short synoicid atrial siphon with an atrial lip from the upper rim of the opening and a small median papillum from the mid-line just behind the atrial aperture. Stomach walls are mulberry-like with rounded pouches in the internal lining. In preservative the test and zooids are a yellowish colour and the preservative is also stained yellow.

Remarks

The specimens, including their colour and the colour of the preservative, are consistent with previous descriptions of this species. A projecting brood pouch containing a single embryo from the postero-dorsal corner of the thorax has been reported in previously described specimens although these pouches were not found in the present material. The mulberry-like stomach, small colony lobes together with the numerous larval lateral ampullae help to distinguish this temperate species.

Figures

Figure 10. In situ images of: (A) Synoicum sacculum (SAM E2864); (B) Synoicum sacculum (SAM E3288); (C) Synoicum sphinctorum (SAM E3283); (D) Aplidium abditum (SAM E3268); (E) Aplidium brevilarvacium (SAM E3284); (F) Aplidium clivosum (SAM E3390); (G) Ascidia scaevola (SAM E2871); (H) Botryllus stewartensis (SAM E3289).