Didemnum jucundum Kott, 2001

Page, M. J., Willis, T. J. & Handley, S. J., 2014, The colonial ascidian fauna of Fiordland, New Zealand, with a description of two new species, Journal of Natural History (J. Nat. Hist.) 48 (27 - 28), pp. 1653-1688 : 1679-1680

Didemnum jucundum Kott, 2001

( Figure 11E )

? Trididemnum spiculatum Kott, 1972: p. 16 .

Didemnum jucundum Kott, 2001: p. 197 –199, fig. 94, 167D, pl. 10G, H.

Material examined

New records: New Zealand, Fiordland , Thompson Sound , Crayfish Heights (45° 14.279’S, 166° 59.566’E, 15 m, encrusting dead black coral (Antipathies fiordensis), coll. M. Page, 31 February 2006, NIWA 10873 ); Bluff Harbour, Tiwai Point wharf pilings (46° 35.5235’S, 168° 21.137’E, 7 m, coll. M. Page, 20 August, 2007, NIWA 68104 ; 46° 35.4739’S, 168° 20.9565’E, 9 m, coll. M. Page, 21 August 2007) .

Previously recorded: Western Australia; Victoria ( Kott 2001); Kangaroo Island , South Australia ( Kott 1972 b).

Description

In Fiordland colonies encrust dead black coral trees ( Figure 11E ). Living colonies are black; the pigment cells are concentrated in the outer test with large stellate spicules 45–75 µm in diameter with 13 rays in optical transverse section. Spicules are less common around zooid thoraces. The zooids are crowded in the test with no obvious systems and numerous large common cloacal apertures (3 mm diameter) occur throughout the colony. The zooids are large (1.5–1.8 mm long) and the thorax has a long oesophageal neck, extending to a large abdomen twice the size of the thorax. The branchial siphon is relatively long, and the atrial aperture is sessile. There is a single large conical testis follicle with 11 coils of the vas deferens. The large larvae (1 mm trunk length) are incubated in the base of the test below the zooids. They have four stout lateral ampullae on each side, adjacent to three median adhesive papillae on long stalks.

Remarks

The colonies described from Fiordland and Bluff Harbour are new records for this species in New Zealand. They represent a range extension of an Australian native. Because of the relative remoteness of the region and hydrodynamics of the fiords, it is possible that this species represents a relict of a Gondwana fauna (see Kott 1985).

Figures

Figure 11. In situ images of: (A) Eudistoma circumvallatum (NIWA 49966); (B) Pseudodistoma cereum (NIWA 49992); (C) Pseudodistoma novaezelandiae (MNP7398) from the Kermadec Islands; (D) Trididemnum shawi sp. nov. (NIWA 10872, holotype); (E) Didemnum jucundum (NIWA 10873); (F) Didemnum lithostrotum (NIWA 49980).