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Aplousobranchia ascidians from two different families were integrated with morphological characteristics and molecular phylogenetic analysis for the first time. The present study employed morphological descriptions (colony structures, tunic, zooids, spicules stigmata and test) and a molecular approach, using a fragment of the mitochondrial cytochrome oxidase I (COI) gene of four Aplousobranchia colonial ascidians Aplidium conicum (98%), Aplidium elegans (98%), Didemnum fulgens (92%) and Trididemnum cyanophorum (94%) from Andaman and Nicobar Islands. Bar-coded sequences were extracted with BLAST format from NCBI and the heritable diversity of the submitted sequences were compared with associated ascidian species. Study revealed that the evolutionary relationship among the ascidian species exhibited the constant clades, which may help for rapid reassessment of morphological characters of the species distributed worldwide. [ABSTRACT FROM AUTHOR]

Background: More than 50 ascidian species distributed in the Palk Bay, Southeast coat of India. Up to a very few molecular work has been performed to determine the evolutionary relationships of ascidians in the world.Objectives: Present study explored the value of mtDNA data in assessing phylogenetic relationships within the family Ascidiacea, Didemnidae, Styelidae, and molecular identification of ascidians from the Palk Bay, Southeast coast of India.Materials and methods: The phylogeny analysis was executed based on mitochondrial cytochrome oxidase subunit I (COI) sequences of ascidian species. A BLASTN search can be run to determine the similarity of an unknown DNA sequence (query) with the collection of all known DNA sequences in GenBank.Result: The BLASTN results showed thatDidemnum candidum, Ascidia ahodoriandStyela clavamatch the other listings for these species in GenBank. Mitochondrial COI gene sequences of collected ascidians were submitted to GenBank and obtained the accession numbers.Conclusion: This study is the first report of molecular identification of ascidian species of the Palk Bay, Southeast coast of India. This information about Palk Bay ascidian communities provides a baseline of general biodiversity of that ecosystem. [ABSTRACT FROM AUTHOR]

Seventy-eight species of Ascidiacea, including 21 new species from deeper waters (about 100 m and occasionally to about 500 m) off Western Australia appear to represent a diverse fauna not previously sampled. The relatively few solitary species taken include two possibly introduced (Styela plicata and S. clava). Large aplousobranch colonies dominate the collections. Aplousobranch species with numerous, small, deeply embedded zooids in massive three-dimensional, vertical and often branched or stalked inflexible colonies supported by embedded sand (Polyclinindae) or calcareous spicules (Didemnidae) are common. Species with flexible stalks (enabling them to respond to prevailing currents) such as Clavelina meridionalis, Sigillina australis and S. cyanea were not taken often. Some known species (e.g. Synoicum chrysanthemum, and Atriolum tubiporum) previously considered rare were taken at these depths in significant numbers. Other unusual taxa (Pseudodiazona longigona and Condominium spp.) are recorded from new locations but do not appear to be common. [ABSTRACT FROM AUTHOR]

Forty-eight species (including nine that are new) of the 288 Didemnidae now known from Australian waters are reported on in the present work. Dredged material is from benthic habitats in inter-reefal areas of the Great Barrier Reef and from deeper water canyons off northeastern and northwestern Tasmania. Collections from shallower waters of Port Davey (western Tasmania) and Kangaroo Island (South Australia) were hand-collected by scuba divers. Seven of the eight known genera of the Didemnidae are represented. Despite this emphasis on sampling in temperate waters, only 14 species (all indigenous) are recorded from around the southern half of the continent. The species diversity of this family is greater in the tropics, with 34 species being recorded. Nearly half of these are known also from the tropical western Pacific and some from the Indian Ocean as well. Tropical indigenous species are relatively few. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Thirty–five species (including eight that are new) of non–didemnid aplousobranch species and 25 phlebobranch (including one new) and stolidobranch species are discussed and a further 42 species in non–didemnid taxa in all suborders are newly recorded. Material was taken by scuba diving in the waters around Kangaroo I. and other southern Australian and Tasmanian locations; and further material was taken by dredge from canyons off the southeastern Continental Slope and from inter–reefal areas in the northern Great Barrier Reef region. The known geographic ranges of many southern Australian species are extended into Tasmanian waters and a new species of Rhopalaea is described from the Tasmanian Canyons. The genera Sigillina and Pseudodistoma are found to be diverse in Australian temperate waters, and they have many characters in common, suggesting a probable phylogenetic relationship that formerly was not recognised. The greatest diversity of species reported is from the vicinity of the northern Great Barrier Reef. Almost without exception these are non–indigenous tropical species often extending into Australian temperate locations where they are sympatric with indigenous species found mainly around the southern half of the continent. Pyura stolonifera has a similar range in temperate Australian waters but appears also to occur on the South African and Chilean coasts in similar habitats and may represent a Gondwana relict. [ABSTRACT FROM AUTHOR]

The majority of the 58 species discussed, including 10 new species, were collected by scuba divers at 5–10?m in waters around Australia. Species are from Leptoclinides (11), Polysyncraton (11), Didemnum (19), Trididemnum (7), Lissoclinum (8), Clitella (1), and Diplosoma (1), and new species are in all except Trididemnum and Diplosoma . Additional characters (including a pyloric vesicle reported previously in the Holozoidae and several unrelated didemnid taxa) have been detected for the monotypic genus Clitella Kott, 2001, which is recorded for only the second time. A review of known Australian ascidian species confirms the Didemnidae as the most speciose ascidian family in these waters. In this family, there appears not to be appreciable gene flow between tropical and temperate waters and few species have a continuous tropical–temperate range. A preponderance of Western Pacific non-indigenous species is in the north, while indigenous species, some probably isolated from related tropical ones, are dominant in the temperate waters of the southern half of the continent. Although intraspecific variation and convergence obscures species differences, some aspects of the living organisms detected in in situ photographs contribute to identification. Keys to Australian didemnid species described since the publication of the Australian Ascidiacea part 4, Didemnidae (Kott 2001) are included. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]