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).