Synoicum syrtis, Kott, 2006

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 201

Synoicum syrtis sp. nov.

( Figure 5A–D )

Distribution

Type locality. Queensland (site no. 144, 17.905 ° S, 146.815 ° E, 63 m, 25 September 2003, CSIRO Biodiversity Survey, holotype QM G308757 ) .

Description

The mushroom-like colony (about 5 cm diameter across the flat upper surface) narrows abruptly to a short basal stalk from the centre of the lower surface.Sand is thick in the outer layer of test but is only moderately crowded in the central test. Long, thin zooids criss-cross in the central transparent test. Zooids of the holotype are darkly pigmented. They have relatively long abdomina and long and thread-like posterior abdomina. The atrial tongue arises from the body wall just anterior to the opening. Both zooids and their arrangement are obscured by sand.

Remarks

The species differs from many others in this genus by the origin of the atrial lip from the body wall anterior to the atrial opening. The atrial opening itself often is on a small siphon with a distinct sphincter muscle. The only other species of the genus which have a similar arrangement of the atrial lip and siphon are Synoicum macroglossum ( Hartmeyer, 1919) which also is a tropical species, and S. papilliferum ( Michaelsen, 1930) , a temperate Australian species. Both these species have large, tough, irregular colonies unlike the mushroom-like colonies of the present species. They all have an external layer of sand, although in the present species and S. papilliferum some sand is present throughout the colony and the external layer is thicker than it is in S. macroglossum , which also lacks sand on the upper surface. Zooids of S. macroglossum and S. papilliferum are similarly long and thread-like, although the former may be larger and have slightly more stigmata. Zooids of the present species are obscured by contraction.

Figures

Figure 5. (A–D) Synoicum syrtis (holotype QM G308757): (A) thorax; (B) abdomen; (C) anterior part of posterior abdomen; (D) end of posterior abdomen. (E, F) Aplidium abditum (holotype SAM E3268): (E) whole zooid; (F) larva. Scale bars: 0.2 mm (A–E); 0.1 mm (F).