New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 2)

Eighteen new species of Didemnidae are included in the 71 species discussed. Two hundred and forty-one species of this family now are known from around the Australian continent. Newly recorded material is from the Western Australian Museum (principally from north-western Australia), the South Australian Museum (from Kangaroo I. and Tasmanian waters) and the Queensland Museum (from Darwin and the Northern Territory). Many of the species recorded from north-western, north-eastern and the north of Australia have a range that extends into the western Pacific and sometimes the western Indian Ocean. Tropical didemnid species seldom extend into temperate Australian waters, where the species are largely indigenous. The genus Didemnum dominates the fauna in both tropical and temperate waters. Of the new species, half are in the genus Polysyncraton (five tropical and four temperate species), four are Lissoclinum spp., two are described in each of the genera Didemnum and Leptoclinides, and one in the genus Diplosoma. Spicules are confirmed as reliable, genetically controlled characters showing little intraspecific variation. Amongst the known species, the unusual colonial organization reported for Leptoclinides glauerti Michaelsen, 1930, with its atrial apertures opening directly on the under surface of the colony, is confirmed. Originally described from a single mutilated part of a colony, the species has been redescribed, and its status in the genus Atriolum validated. Trididemnum pseudodiplosoma (Kott, 1962), formerly known only from South Australia, is found to extend into tropical waters of the Northern Territory and the Coral Sea; and Didemnum incanum (Herdman, 1899) appears to be one of the few known species with a trans-Tasman range.