Diplosoma listerianum ( Milne-Edwards, 1841 )

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 : 1681-1682

Diplosoma listerianum ( Milne-Edwards, 1841)

( Figure 13A )

Leptoclinum listerianum Milne-Edwards, 1841: p. 300 .

Diplosoma listeri Lahille, 1890: p. 104 , figs 58–60, 62, 65–69.

Diplosoma macdonaldi Herdman, 1886 ; Brewin, 1946, 1948, 1950b, 1951. Diplosoma listerianum Rowe, 1966: p. 458 (see Kott 2001 for synonymy).

Material examined

New records: Nine Fathom Passage, Dusky Sound (45° 44.237’S, 166° 53.199’E, 14 m, 31 February 2009, NIWA 49936 , two colonies); Caswell Sound, Paua Bay (45° 01.01’S, 167° 08.40’E, 18 m, 2 March 2009, NIWA 49988 ) .

Previously recorded: tropical to temperate waters of the Pacific, Atlantic, Indian oceans and the Mediterranean and North Seas (See Kott 2001); New Zealand, Hauraki Gulf ( Brewin 1948, 1951); Napier ( Brewin 1952b); Cook Strait ( Brewin 1960); Christchurch ( Brewin 1950b); Portobello Peninsula ( Brewin 1946); Stewart Island ( Brewin 1958a).

Description

Colonies are thin translucent, encrusting gelatinous sheets, often overgrowing brachiopods and other sessile fauna. The zooids are visible in the tunic and they are grey, sometimes brown due to dark pigment on the thorax and sometimes the abdomen ( Figure 13A ). The zooids are supported by a basal tunic connective in the cloacal cavity. The zooids are approximately 1.0 mm long with a retractor muscle originating halfway down the oesophageal neck and usually an oesophageal bud. There are two testis follicles with a straight vas deferens. Large spherical embryos (1.2 mm trunk length) are present in all Fiordland specimens. They have two pairs of long lateral ampullae and three median adhesive papillae.

Remarks

The absence of a black pigment spot in the dorsal mid-line anterior to the atrial aperture in specimens from Fiordland may be an artefact of preservation or intraspecific variation; different colonies can vary greatly in the amount of pigment. Because the colonies were soft and gelatinous, collapsed when sampled, and their larvae had only two pairs of ampullae, we are confident the species from Fiordland is D. listerianum .

Figures

Figure 13. In situ images of: (A) Diplosoma listerianum (NIWA 49936); (B) Diplosoma velatum (NIWA 49990); (C) Diplosoma velatum (NIWA 49991).