Pseudodistoma cereum Michaelsen, 1924

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 : 1675-1676

Pseudodistoma cereum Michaelsen, 1924

( Figure 11B )

Pseudodistoma cereum Michaelsen, 1924: p. 364 –374, fig. 17. Brewin, 1958a: p. 444.

Material examined

New records: Caswell Sound , Paua Bay (45° 01.01’S, 167° 08.40’E, 15 m, 3 February 2009, NIWA 49987 ) ; Doubtful Sound , Hare’ s Ears (45° 16.218’S, 166° 50.532’E, 7 m, 2 February 2006, NIWA 49992 ) ; Tiwai Point (46° 35.5235’S, 168° 21.137’E, 10 m, 20 August 2007, MNP9170 ) ; Spirit’ s Bay (34° 25.200’S, 172° 50.900’E, 10 m, 12 February 2002, MNP7218 ) ; Tom Bowling Bay (34° 24.736’S, 172° 57.295’E, 20 m, 3 July 2003, MNP7353 ) ; Three Kings Islands (34° 10.662’S, 172° 02.792’E, 15 m, 24 April 2002, MNP7042 ) .

Previously recorded: New Zealand; Portobello Peninsula ( Millar 1982); Stewart Island ( Michaelsen 1924; Brewin 1958a); Otago Coast ( Brewin 1958a).

Description

Cream-coloured, club-shaped colonies with a thick basal mat are common in subtidal environments throughout New Zealand. The colony morphology can vary with wave exposure. For example, colonies collected from the exposed Fiordland outer coast (NIWA 49992, Figure 11B ) are encrusting without the distinctive lobes common in deep subtidal environments. The test is opaque and cartilaginous with zooids opening separately on raised dimples. Test cells are common in the outer test and immediately around the zooids. The zooids are large, measuring 15 mm for the post-abdomen and 5 mm for the thorax and abdomen. The branchial sac has three rows of stigmata and there is a long oesophagus entering a stomach with four folds. Up to 10 embryos are incubated serially in the thoracic region of the oviduct. Larvae measure 1.5 mm trunk length and have five pairs of distinct bi-lobate lateral ampullae surrounding the adhesive papillae and posterior vesicles.

Remarks

All Pseudodistoma cereum specimens examined in this study, both from the North and South Island, have four distinct stomach folds. Of the other common species in northern New Zealand, Pseudodistoma novaezelandiae (Brewin, 1950) can be distinguished by bright orange stalked colonies ( Figure 11C ), and zooids with a smooth-walled stomach.

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).