Taxonomic affinities of three stalked colonial species of the Ascidiacea (Tunicata) from the central coast of New South Wales and indications of a trans‐Tasman connection

Abstract

Three colonial aplousobranch ascidian species from the central coast of New South Wales were originally described from one of the earliest significant regional collections of Australian ascidians (Herdman, 1899). They have a similar habit, their colonies being long, oval to cylindrical gelatinous heads on relatively short, thick, fleshy stalks and they all respond in the same way to the multidirectional currents to which they are subjected in the habitats they occupy. Nevertheless, they are not closely related phylogenetically. One is the monotypic Euclavella claviformis (Herdman, 1899), known only from the central eastern Australian coast and the North Island (New Zealand). The second species is the indigenous Hypsistozoa distomoides (Herdman, 1899), known from the Great Australian Bight and the central eastern coast of Australia but related closely to the only other species known in this genus, its type species H. fasmeriana (Michaelsen, 1924), known only from New Zealand. The third species discussed, Sigillina cyanea (Herdman, 1899), an indigenous Australian species known from a wide range around the Australian continent, has no closely related species in the indigenous New Zealand fauna although a similar and partly sympatric species Sigillina australis (Savigny, 1816) does occur in New Zealand. A close relationship of Sigillina to the Pseudodistomidae (rather than the Holozoidae) is apparent. Larvae of H. distomoides are found to have characters formerly known only in larvae of the type species (see Brewin 1956, 1959).

Keywords:

• Holozoidae
• Pseudodistomidae
• Pycnoclavellidae
• Euclavella
• Sigillina
• Hypsistozoa
• ectotrophic membranes
• endodermal tubes
• vegetative stolon
• viviparity

Acknowledgements

The specimens discussed here are part of a very small collection made by the experienced marine invertebrate photographer, Neville Coleman, whose in situ images of the species in question adorn this work. Much of our understanding of living ascidians in their natural habitat derives from his pioneering underwater photography of marine organisms from the early 1970s, from his careful indexing of the photographs to the fixed material and the high quality and biological integrity of his images, which he preserves in the Australian Marine Photographic Index. Additional material of Hypsistozoa distomoides from Port Stephens has been contributed by Dr. Tim Glasby and other members of the NSW Fisheries Dept. stationed at Port Stephens.

I am grateful also to the Director and Board of the Queensland Museum for their continuing support of this project by providing laboratory accommodation and infrastructure. My research assistant Eileen Salisbury scanned the colour photographs, helped in the preparation of slides, drew the black and white figures, maintained the database of specimens and helped to collate the final manuscript. This assistance is provided by a grant from the Australian Biological Resources Survey (ABRS) and I am grateful for the continuing support of that agency.