Atriolum bucinum Kott, 2001

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 : 1165-1166

Atriolum bucinum Kott, 2001

Atriolum bucinum Kott, 2001, p. 21 .

Distribution

Previously recorded (see Kott 2001): Western Australia (Houtman’s Abrolhos). New record: Western Australia CSIRO SS10/05 (Cape Mentelle, Stn 15, 97 m, 21.11.05, QM G328447).

The species is recorded only from the southern section of the western Australian coast.

Description

The newly recorded colony is biramous, divided into two equal sized stumpy lobes, 5 cm high overall, with a large terminal common cloacal aperture on each lobe. The common cloacal cavity is continuous through the two lobes. The zooids are confined to the thin layer of test around the outside of the colony with the branchial siphons opening around the outside and the long atrial siphons opening directly into the central cavity. The spicules are stellate, with 9–11 conical pointed rays in optical transverse section and they are relatively large, to 0.1 mm diameter. They are crowded in the test and the colony is raspy to the touch as a result of the spicules in the surface. Spicules are present throughout the test, although they are most crowded in the surface.

Remarks

The colony, zooids and spicules appear to agree with the type material in all respects except for the everted rim of the common cloacal apertures. It is possible that the everted margin of these apertures is dependent on a degree of relaxation of the colonies. Certainly the present colony appears to be contracted. It has been cut in half, presumably before fixation. The continuous large common cloacal cavity is a characteristic of this species, as are its large spicules with relatively few rays. Atriolum irregulare Kott, 2007 from Tasmania has spicules of a similar size but with more and longer rays and its colonies are less regular and quite different from the present species .