Clavelina simplex, Kott, 2006

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 182-183

Clavelina simplex sp. nov.

( Figure 1D, E )

Distribution

Type locality. Tasmanian Canyons (Banks Strait, 168 m, 25 April 2004, Sherman sled, four syntypes, QM G308824 ) .

Description

Colonies are short, rather stumpy cylinders, upright, up to 3 cm high and 1.5 cm diameter with the upper end rounded. The upper half to two-thirds of the colony is naked and transparent and the lower third to half is slightly translucent and has particles of sand and shell adhering to it. The base of the colony is irregular and has some sand attached to it. Up to 10 zooids are in each colony and open in what appears to be a circle around the upper surface. The test is darkly pigmented around the apertures. Conspicuous clusters of terminal ampullae of the fine-branching vascular stolons are in the test around the periphery of the lower two-thirds of the colony. The type material is crushed and mutilated and details of the zooid morphology are obscure. The branchial aperture is terminal and the atrial aperture is sub-terminal. Juvenile gonads are in the gut loop.

Remarks

Although the zooids in the present colonies are not well preserved and few adult organs are distinguishable, the species is readily recognised as belonging to this family Clavelinidae by the conspicuous clusters of crowded terminal ampullae and prolific branches of the test vessels that are known to be the site of replication. Clavelinidae , an aplousobranch family, is separated from others by its unique method of vegetative replication—budding in terminal ampullae of the test vessel.

The new species is distinguished from others in the genus by its very simple colony with a circle of relatively short zooids around the top of each independent vertical lobe and by the profusion of terminal ampullae of test vessels that crowd the central test in the thick, cylindrical stalk behind the zooids. In its short zooids it most resembles the indigenous southern Australian species Clavelina cylindrica , which also has a large number of terminal ampullae. Clavelina cylindrica is a commonly encountered species in temperate Australian waters (Cockburn Sound to Bowen; Kott 1990a) but its zooids are only partially embedded clearly distinguishing it from the present species.

In his notes on Distomidae, Caullery (1909) reported on a specimen from Western Port collected by Quoy and Gaimard that resembled Polyclinum cylindricum Quoy and Gaimard, 1834 (< Clavelina cylindrica ) and had terminal ampullae of the test vessels that resemble those found in the present species. He assigned it to Chondrostachys Macdonald, 1858 (type species C. macdonaldi Bronn, 1862 from Bass Strait), a genus of the Clavelinidae , with relatively few longitudinal muscles, triradial adhesive organs, the anal opening near the atrial aperture and buds forming in the terminal ampullae of test vessels. (It had been noted in a footnote to Macdonald’s paper by the editor of the journal Annals and Magazine of Natural History (1858) that Chondrostachys resembled the Clavelinidae closely; and subsequently Chondrostachys macdonaldi was recognised as a junior synonym of Clavelina cylindrica ).

The genus Clavelina is well represented in the temperate ascidian fauna of Australia and world-wide by a number of colonial species with partially embedded zooids ( C. cylindrica , C. australis , C. moluccensis , C. pseudobaudinensis ), some with completely embedded zooids ( C. baudinensis ) and a few solitary or almost solitary ones ( Clavelina dagysa , C. ostrearium ). One other monotypic genus of the family, Euclavella ( E. claviformis ) with completely embedded zooids, also is known from temperate waters of Australia and New Zealand. Clavelinidae is not represented in the sub-Antarctic or Antarctic and its diversity in temperate Australian waters may be the result of isolation from the tropical fauna. The presence of this new species in the southern Ocean may also be a result of its isolation from a related temperate species.

Figures

Figure 1. (A–C) Rhopalaea meridionalis: (A, C) holotype QM G308821; (B) paratype QM G308825). (A) Whole zooid (in the test, showing position of gut loop); (B) thorax; (C) abdomen. (D, E) Clavelina simplex sp. nov. (QM G308824, syntype): (D) colony; (E) branching vascular stolons with terminal ampullae. Scale bars: 5 mm (A, C, D); 1 mm (B, E).