Trididemnum pigmentatum 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 : 2457-2458

Trididemnum pigmentatum Kott, 2001

( Figures 17C , 21C )

Trididemnum pigmentatum Kott 2001, p 278 and synonymy; 2004b, p 2503; 2004c, p 40.

Distribution

Previously recorded (see Kott 2001, 2004b): Western Australia (Kimberley, Montebello Is); Queensland (Hervey Bay–Lizard I.); Northern Territory (Darwin); Indonesia; Fiji. New record: Northern Territory (Bynoe Harbour, QM G308714).

Description

Living colonies have a smooth, even surface, although sometimes lobes overgrow the surface as the colony grows. They have a pearly appearance resulting from the layer of white, crowded spicules beneath a thin superficial layer of bladder cells and minute black pigment particles mixed with the bladder cells. Some yellow pigment is around the common cloacal apertures and also is present internally. Deep primary common cloacal canals extend into posterior abdominal cavities and are lined with a layer of spicules. Spicules are patchy or sparse in the remainder of the colony. Faecal pellets are in the basal test. The large, stellate spicules (to 0.12 mm diameter) have 13–15 long, narrow conical pointed rays in optical transverse section. Zooids are of the usual form with a short posterior atrial siphon and a short robust retractor muscle at the posterior end of the thorax.

Remarks

The colony has a superficial resemblance to the equally smooth-surfaced Leptoclinides brandi , although the latter species has spicules at the surface making it raspy to the touch, and also the species are readily separated by their generic characters. The present species is separated from most other Trididemnum species by its large spicules with numerous finely pointed rays. Although T. savignii has similar spicules, it has eight rather than 10 vas deferens coils.

Some living colonies are reported to have been black (see Kott 2004a), possibly the result of a greater intensity of black pigment in the surface test.

Figures

Figure 17. Scanning electron micrographs of the calcareous spicules of: (A) Trididemnum dispersum (WAM 1044.89); (B) Trididemnum nobile (SAM E3262); (C) Trididemnum pigmentatum (QM G308714); (D) Lissoclinum agriculum sp. nov. (WAM 179.93, syntypes); (E) Lissoclinum bistratum (WAM 1018.89); (F) Lissoclinum clavatum sp. nov. (SAM E3260, holotype); (G) Lissoclinum coactum (WAM 120.90); (H) Lissoclinum diversum (WAM 153.86).

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).