Didemnum mantile Kott, 2001

Kott, Patricia, 2007, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 4), Journal of Natural History 41 (17 - 20), pp. 1163-1211 : 1183-1184

Didemnum mantile Kott, 2001

( Figures 3A , 8H )

Didemnum mantile Kott 2001, p 203 ; 2005a, p 2447.

Distribution

Previously recorded (see Kott 2005a): South Australia (eastern end of Mason Bay , Franklin I.); Victoria (Westernport). New record: Tasmanian Canyons (Banks Strait, 40.64025 – 40.68686 ° S, 148.78784– 148.80762 ° E, 168 m, QM G308887 ) .

Description

The mosaic of small, translucent, pink, single system colonies, each with a single common cloacal aperture in the middle of the upper surface, are epibionts on the test of a specimen of Polycarpa υiridis. Some are small, from about 0.5 cm diameter, and one is a larger, irregular scrap of about 1.5 cm maximum diameter. The small, stellate spicules (to 0.04 mm diameter, with seven to nine stumpy conical rays in optical transverse section) are crowded throughout the colony. The horizontal, thoracic common cloacal cavity is shallow. The small brownish zooids have four rows of stigmata and a large atrial aperture with its upper lip produced out from the zooid. A short retractor muscle projects from one-third of the way down the oesophageal neck. Well-developed larvae have 10 pairs of rounded lateral ampullae, although fewer are in less well-developed larvae. The larval trunk is 0.6 mm long.

Remarks

A number of species with small colonies and zooids are known in this genus. These usually can be distinguished by aspects of their colonies, larvae and/or spicules, namely Didemnum minisculum Kott, 2001 has fewer spicule rays and smaller and more transparent colonies; D. incanum ( Herdman, 1899) also has fewer spicule rays and different colonies and larvae; and both D. lissoclinum Kott, 2001 and D. pecten Kott, 2001 have different colonies and larger spicules with more rays.

The larvae of the present species, described here for the first time, are distinctive in their 10 pairs of larval lateral ampullae in a relatively short trunk.

Figures

Figure 3. (A) Didemnum mantile (QM G308887): larva. (B) Didemnum microthoracium (SAM E3259): colony. (C, D) Didemnum parau (QM G308859): (C) abdomen; (D) larva. Scale bars: 0.1 mm (A, C, D), 5 mm (B).

Figure 8. Scanning electron micrographs. (A) Didemnum coralliforme (QM G308861); (B) Didemnum crescente (QM G308815); (C) Didemnum fragum (QM G308826); (D) Didemnum grande (QM G308867); (E) Didemnum granulatum (QM G308843); (F) Didemnum jedanense (QM G308846); (G) Didemnum lissoclinum (QM G308814); (H) Didemnum mantile (QM G308887).