Aplidium clivosum Kott, 1992

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234 : 204-205

Aplidium clivosum Kott, 1992

( Figure 10F )

Aplidium clivosum Kott 1992a, p 530 and synonymy.

Distribution

Previously recorded (see Kott 1992a): Western Australia (from Port Hedland to Hamelin Bay on the south-western coast) ; South Australia (Great Australian Bight to Nuyts and Eyre Peninsulas, Kangaroo I., Gulf St Vincent) ; New South Wales ( Jervis Bay ); Queensland (Capricorn Group). New record : Tasmania ( Forestier Peninsula , 8–15 m, SAM E3390 ) .

Description

The newly recorded specimen has the characteristic appearance of these large, conspicuous cushion- to tabular-shaped colonies, with a more or less horizontal upper surface where rows of zooids are along each side of common cloacal canals converging to large protuberant common cloacal apertures. Rounded marginal elevations on the upper surface surround each large cloacal system as well as the outside margin of the colony. The sides of the colonies are encrusted with sand, which also is present throughout the test, absent only from around the thoraces along each side of the shallow radial common cloacal canals. The sand can be seen in radial lines intruding in toward the common cloacal apertures between the double rows of zooids.

Zooids are distinctive with conspicuous sphincter muscles, a large atrial lip well removed from the apertures and five gastric folds. Colonies are invariably some shade of pink to red.

Remarks

Other species with similar systems depressed into the upper surface of the colony and similar zooids with conspicuous siphonal muscles and separate atrial tongues are A. cratiferum ( Sluiter, 1909) and A. grisiatum Kott, 1998 . The former can only be distinguished by its cloacal systems with the zooids opening around a central cavity rather than along each side of converging canals. The latter can be distinguished only by its more numerous gastric folds. Many of the Aplidium spp. (see Kott 1992a) have similar zooids to the present species, with conspicuous sphincters, separate atrial apertures and five stomach folds, but they have long, branched or circular common cloacal canals rather than central chambers or cavities or radial canals.

Species in other genera, namely the temperate Aplidiopsis mammillata Kott, 1992a , and the tropical Synoicum castellatum Kott, 1992a , also have similar colonies, although the latter has cloacal systems more like A. cratiferum and both are readily distinguished by their generic characters.

The present species, unlike A. caelestis , appears to be an indigenous Australian species. It has been recorded from temperate locations more often than from the tropics, although it does extend up both the western and eastern coast of Australia.

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).