Didemnum cygnuus 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 : 2440-2441

Didemnum cygnuus Kott, 2001

( Figures 15G , 19H )

Didemnum cygnuus Kott 2001, p 169 ; 2004c, p 40.

Distribution

Previously recorded (see Kott 2001): Western Australia (Swan River estuary, Port Hedland ). New record: Northern Territory ( Bynoe Harbour , QM G308716 ) .

Description

The newly recorded colony is a thin film of test, greenish grey in life, with sparse but evenly distributed spicules, growing over and around pebbles and incorporating them into the test. Spicules are stellate, to 0.05 mm diameter, with five to seven sturdy conical rays in optical transverse section. Zooids are small, with a short retractor muscle and five coils of the vas deferens.

Remarks

The thin colonies and their small, sturdy, stellate spicules with few conical rays, some of which are particularly thick, are characteristic of this species, which previously was known only from Western Australia.

Figures

Figure 15. Scanning electron micrographs of the calcareous spicules of: (A) Polysyncraton millepore (WAM 122.93); (B) Polysyncraton orbiculum (WAM 128.90); (C) Polysyncraton papyrus (SAM E3253); (D) Didemnum astrum (WAM 601.89); (E) Didemnum cilicium sp. nov. (SAM E3251, holotype); (F) Didemnum corium sp. nov. (SAM E3249, holotype); (G) Didemnum cygnuus (QM G308716); (H) Didemnum fragum (SAM E3266).

Figure 19. In situ images of: (A) Polysyncraton glaucum (QM G308736); (B) Polysyncraton papyrus (SAM E3253); (C) Polysyncraton pedunculatum (SAM E3272); (D) Polysyncraton purou (QM G308707); (E) Polysyncraton rica (SAM E3245); (F) Didemnum cilicium (SAM E3251, holotype); (G) Didemnum corium (SAM E3249, holotype); (H) Didemnum cygnuus (QM G308716).