Synoicum laboutei

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1138-1139

Synoicum laboutei F. and C. Monniot, 2006

( Figures 5D, E )

Synoicum laboutei Monniot F. and C. 2006, p. 129.

Distribution

Previously recorded (see Monniot F. and C. 2006): Malagasy. New record: Western Australia, CSIRO SS10/05 (Cape Mentelle, Stn 15, 97 m, 21.11.05, QM G328443).

Description

The colony is a vertical cone about 6 cm high and 3 cm diameter consisting of a single common cloacal system. About 16 vertical paired rows of zooids (a row along each side of parallel common cloacal canals) are on the pink upper half of the colony converging to the terminal common cloacal aperture. Sparse sand is embedded in the internal test, especially in the lower half of the colony but is absent from the test around the red common cloacal aperture and the rows of zooids. Sand is present in the surface test between the double rows of zooids. The zooids are particularly contracted. A strongly muscular atrial lip protrudes from the body wall anterior to the small atrial siphon. The thoraces have strong muscles down each side and are contracted. The abdomina and posterior abdomina are also contracted and twisted. Each zooid can be seen to have a long oesophagus, a small, smooth-walled stomach halfway down the abdomen, a long duodenal area and a small posterior stomach at the posterior end of the abdomen. Muscle bands from the abdomen continue along the posterior abdomen and, in this specimen, these muscles are contracted and the outside of the posterior abdomen is gathered into a frill along each side so that it appears to be especially broad. It is separated from the abdomen by a narrow constriction.

Remarks

The only two records of this species are separated by a vast distance. The species is readily identified by the strawberry-like appearance of the colonies, each a single common cloacal system consisting of parallel double rows of zooids arranged evenly around the colony converging to the terminal common cloacal aperture. The specimens appear to be identical with the exception only of the thread-like posterior abdomen of the type specimen and its lack of a constriction between the abdomen and posterior abdomen. The presence of this constriction suggests that the species may be in the genus Aplidiopsis especially as the posterior abdomina of Aplidiopsis are not always short or fusiform-shaped sacs and sometimes are long (see Aplidiopsis indicus F. and C. Monniot, 2006) like those of the present species. Aplidiopsis can be distinguished by its delicate muscles, which seldom extend beyond the anterior half of the thorax, and by the twisted distal end of the gut loop (involving the vas deferens). This twist has not been reported for species of Synoicum (including the present specimens).

Figures

Figure 5. Synoicum implicatum sp. nov. (QM G328098): A, colony; B, thorax and abdomen; C, antero-dorsal part of thorax. Synoicum laboutei (QM G328443): D colony; E, thorax and abdomen, both very much contracted. Synoicum macroglossum (QM G328104): F, thorax; G, abdomen and posterior abdomen. Synoicum obscurum (QM G328461): H, larva. Scales: A, D, 2.0 cm; B, 1.0 mm; C, E–G, 0.5 mm; H, 0.1 mm.