Didemnum jucundum Kott, 2001

Kott, Patricia, 2005, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3), Journal of Natural History 39 (26), pp. 2409-2479 : 2446

Didemnum jucundum Kott, 2001

( Figures 8B , 20D )

Didemnum jucundum Kott 2001, p 197 and synonymy; 2004b, p 2495.

Distribution

Previously recorded (see Kott 2001, 2004b): Western Australia (Esperance); South Australia (Kangaroo I.,?West I.); Tasmania (Forestier Peninsula). New record: Tasmania (Tasman Peninsula, SAM E3236).

Description

The preserved colony is a flexible thin sheet with spicules evenly distributed throughout, but not crowded. The zooids can be seen through the test, conferring a pinkish glow to the colony. The test tears readily and has the consistency of cotton wool. Zooids are readily removed from it. Although spicules to 0.82 mm diameter have been reported previously, the maximum diameter detected in the newly recorded specimen is 0.066 mm. Spicules have 13–15 crowded, conical rays in optical transverse section. Large common cloacal apertures with spicule-free rims are scattered randomly on the surface. Zooids have relatively long cylindrical branchial siphons that make small bumps on the surface of the colony. The atrial apertures are sessile and lack an atrial tongue. They have a particularly strong retractor muscle that is free of the zooid from about halfway down its long oesophageal neck. Gonads were not detected in the newly recorded specimen.

Remarks

The species can be distinguished by its zooids with a long cylindrical branchial aperture, the retractor muscle branching away from the zooid well down the long oesophageal neck and the characteristic spicules with crowded conical rays. It is known only from the southern temperate waters of the continent.

Figures

Figure 8. (A) Didemnum incanum (SAM E3252): colony surface; (B) Didemnum jucundum (SAM E3236): thorax; (C) Didemnum microthoracicum (SAM E3256): surface view of a circle of thoraces surrounding a test connective. Scale bars: 1.0 mm (A); 0.1 mm (B, C).

Figure 20. In situ images of: (A) Didemnum fragum (SAM E3266); (B) Didemnum fuscum (QM G308730); (C) Didemnum incanum (SAM E3252); (D) Didemnum jucundum (SAM E3236); (E) Didemnum leopardus (QM G308719, holotype); (F) Didemnum microthoracicum (SAM E3256); (G) Didemnum moseleyi (QM G308713); (H) Didemnum pellucidum (SAM E3271).