Trididemnum savignii ( Herdman, 1886 )

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 : 2458

Trididemnum savignii ( Herdman, 1886)

( Figure 21D )

Didemnum savignii Herdman 1886, p 261 .

Trididemnum savignii: Kott 2001, p 281 ; 2002a, p 39; 2004b, p 2504; 2004c, p 40.

Distribution

Previously recorded (see Kott 2001, 2004b): Western Australia (Nares Rock); Queensland (Heron I.–Lizard I.); Northern Territory (Darwin); Indonesia;?Florida; Bermuda. New record: Northern Territory (Bynoe Harbour, QM G308721).

Description

The colonies are robust, and grey, with a translucent test and a fleshy superficial aspicular layer overlying a layer of spicules. Spicules also line the common cloacal cavity. The spicules are large, to 0.11 mm diameter with 11–13 pointed rays in optical transverse section. Faecal pellets are embedded in the basal test.

Zooids are small, with black squamous epithelium on the abdomen and especially on the anterior part of the thorax, although an endostylar pigment cap was not detected. A long retractor muscle projects from the posterior end of the thorax. Eight coils of the vas deferens surround the undivided testis.

Remarks

The species superficially resembles T. areolatum from which it is distinguished by the finely pointed rays of its stellate spicules. The colonies do not form such complex, spongy threedimensional reticula as T. sibogae or T. nobile , both of which also can be separated from the present species by their spicules with fewer rays. The spicules are slightly smaller than, but otherwise similar to, those of T. pigmentatum from which the present species can be distinguished by its thick, fleshy and pigmented superficial layer of test.

Figures

Figure 21. In situ images of: (A) Trididemnum amiculum (SAM E3263); (B) Trididemnum nobile (SAM E3262); (C) Trididemnum pigmentatum (QM G308714); (D) Trididemnum savignii (QM G308721); (E) Lissoclinum calycis (QM G308749); (F) Lissoclinum clavatum (SAM E3260, holotype); (G) Lissoclinum concavum (SAM E3242); (H) Lissoclinum levitum (SAM E3254).