Whale fall chemosymbiotic communities in a southwest Australian submarine canyon fill a distributional gap.

A whale fall community of chemosymbiotic invertebrates living on cetacean bones has been identified off southwestern Australia during a Remotely Operated Vehicle (ROV) survey at bathyal depths within the Bremer Marine Park, which is part of important marine mammal areas (IMMA) of the Albany Canyon Region. Cetacean bones on the seafloor of the Hood Canyon, consisted of isolated skulls of three species of beaked whales (family Ziphiidae): Mesoplodon cf. layardii, M. grayi, and M. hectori, a few vertebrae, and lower jaws. One of the beaked whale skulls (Mesoplodon cf. layardii) was sampled and found to be intensely colonised by hundreds of specimens of a bathymodilinae mussel ("Adipicola" s.l.). Live polychaetes (Phyllochaetopterus?), skeneimorph gastropods, and amphipods (Seba, Leptamphopus) colonised the skull bone, which represent a later stage (sulfophilic) of carcass decomposition. The reducing sediment below the skull was inhabited by lucinid (Lucinoma) and vesicomyid (Calyptogena) chemosymbiotic bivalves. Additionally, the sediment thanatocoenosis comprised shells of various other chemosymbiotic bivalves, such as Acharax, thyasirids, lucinids, vesicomyids, and limpets, representing the complex ecological turnover phases through time in this whale fall chemosynthetic habitat. With one exception, all bones recovered were colonized by bathymodiolin mussels. This is the first documented case of a chemosynthetic community and associated chemosymbiotic fauna relating to beaked whales, and the first fully documented record of a whale fall community within the Australian Southern Ocean region.

The sponge crabs of Western Australia and the Northwest Shelf with descriptions of new genera and species (Crustacea: Brachyura: Dromiidae).

The Dromiidae of Western Australia are summarized primarily based on specimens from the collection of the Western Australian Museum and some additional material from the Australian Museum, Sydney. The genus Alainodromia McLay 1998, is recorded from Camden Sound, Australia, as a new species Alainodromia dambimangari sp. nov. New evidence suggests that the species of Alainodromia are very likely shell carriers that also have direct development. Five species of Cryptodromia are reported from Western Australia and a new genus, Baccadromia gen. nov., is erected for Dromia (Cryptodromia) bullifera Alcock, 1900. The genus Lamarckdromia Guinot Tavares, 2003 is revised and now includes three species: L. beagle sp. nov., L. excavata (Stimpson, 1858) and L. globosa (Lamarck, 1818). Six species of Dromiidae are new to Australia: Baccadromia bullifera (Alcock, 1900), Cryptodromia amboinensis (De Man, 1888), C. pileifera Alcock, 1901, Epigodromia rotunda McLay, 1993, and Foredromia rostrata McLay, 2002. New records for Western Australia include: Cryptodromia hilgendorfi De Man, 1888, Epigodromia areolata (Ihle, 1913) and Lewindromia unidentata (Rppell, 1830). A total of 31 species of dromiid crabs are now known from Western Australian coast with five species endemic to the state. There are more than 40 species of Dromiidae known from Australia of which about 40% are endemic.

Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean.

There is a growing interest in the exploitation of deep-sea mineral deposits, particularly on the abyssal seafloor of the central Pacific Clarion-Clipperton Zone (CCZ), which is rich in polymetallic nodules. In order to effectively manage potential exploitation activities, a thorough understanding of the biodiversity, community structure, species ranges, connectivity, and ecosystem functions across a range of scales is needed. The benthic megafauna plays an important role in the functioning of deep-sea ecosystems and represents an important component of the biodiversity. While megafaunal surveys using video and still images have provided insight into CCZ biodiversity, the collection of faunal samples is needed to confirm species identifications to accurately estimate species richness and species ranges, but faunal collections are very rarely carried out. Using a Remotely Operated Vehicle, 55 specimens of benthic megafauna were collected from seamounts and abyssal plains in three Areas of Particular Environmental Interest (APEI 1, APEI 4, and APEI 7) at 3100-5100 m depth in the western CCZ. Using both morphological and molecular evidence, 48 different morphotypes belonging to five phyla were found, only nine referrable to known species, and 39 species potentially new to science. This work highlights the need for detailed taxonomic studies incorporating genetic data, not only within the CCZ, but in other bathyal, abyssal, and hadal regions, as representative genetic reference libraries that could facilitate the generation of species inventories.

Surveying keratose sponges (Porifera, demospongiae, Dictyoceratida) reveals hidden diversity of host specialist barnacles (Crustacea, Cirripedia, Balanidae).

Sponges represent one of the most species-rich hosts for commensal barnacles yet host utilisation and diversity have not been thoroughly examined. This study investigated the diversity and phylogenetic relationships of sponge-inhabiting barnacles within a single, targeted host group, primarily from Western Australian waters. Specimens of the sponge order Dictyoceratida were surveyed and a total of 64 host morphospecies, representing four families, were identified as barnacle hosts during the study. Utilising molecular (COI, 12S) and morphological methods 42 molecular operational taxonomic units (MOTUs) of barnacles, representing Acasta, Archiacasta, Euacasta and Neoacasta were identified. Comparing inter- and intra-MOTU genetic distances showed a barcode gap between 2.5% and 5% for COI, but between 1% and 1.5% in the 12S dataset, thus demonstrating COI as a more reliable barcoding region. These sponge-inhabiting barnacles were demonstrated to show high levels of host specificity with the majority being found in a single sponge species (74%), a single genus (83%) or a single host family (93%). Phylogenetic relationships among the barnacles were reconstructed using mitochondrial (12S, COI) and nuclear (H3, 28S) markers. None of the barnacle genera were recovered as monophyletic. Euacasta was paraphyletic in relation to the remaining Acastinae genera, which were polyphyletic. Six well-supported clades of molecular operational taxonomic units, herein considered to represent species complexes, were recovered, but relationships between them were not well supported. These complexes showed differing patterns of host usage, though most were phylogenetically conserved with sister lineages typically occupying related hosts within the same genus or family of sponge. The results show that host specialists are predominant, and the dynamics of host usage have played a significant role in the evolutionary history of the Acastinae.

Description of a new species of Membranobalanus (Crustacea, Cirripedia) from southern Australia.

A new species of sponge-inhabiting barnacle, Membranobalanus porphyrophilus sp. nov., is described herein. This species can be distinguished from all other congeners by a combination of characters, in particular by the shapes of the tergum and scutum and the armament of the cirri. COI sequence data from the type specimens have been lodged with GenBank and a morphological key to the species of Membranobalanus is provided to aid future research. The host of the new species is the southern Australian endemic demosponge Spheciospongia purpurea. The new species of barnacle is thought to be host species specific.

Descriptions of four new sponge-inhabiting barnacles (Thoracica: Archaeobalanidae: Acastinae).

Within the family Archaeobalanidae, the sponge-inhabiting barnacles include species from the subfamilies Acastinae and Bryozobiinae as well as from the genus Membranobalanus in the subfamily Archaeobalaninae. Members of these groups are obligatory symbionts of poriferans, but the Acastinae can also be found in association with alcyonaceans and antipatharians. Acasta sulcata Lamarck, 1818, is one of the most widely reported sponge-inhabiting barnacle species, with numerous records across the Indo-West Pacific region revealing significant morphological variation. A combined morphological and molecular approach has revealed high diversity in recent collections of sponge-inhabiting barnacles in Taiwan and Australia, and four new species, namely Acasta aspera sp. nov., Acasta huangi sp. nov., Acasta radenta sp. nov., and Acasta undulaterga sp. nov., have been described here. All four species are morphologically close to A. sulcata, and the morphological similarity between these proposed species has led to the proposal of a "sulcata species complex."

Description of a new species of brooding spider crab in the genus Paranaxia Rathbun, 1924 (Brachyura: Majoidea), from northern Australia and Indonesia.

A new species, Paranaxia keesingi sp. nov., is described based on specimens collected in northern Australia. The new species differs from its only congener, P. serpulifera (Guérin, 1832, in Guérin-Méneville 1829-1837), by several characters including carapace setation, sternal cavities, absence of a subhepatic spine, presence of a sharp spine on the posterodistal angle of the cheliped merus, relatively shorter chelipeds, and longer and more slender ambulatory legs. Morphological separation of the two species is supported by 12s rDNA sequence divergences of 7.4-8.2%. Like P. serpulifera, the newly described species exhibits direct development with females carrying juvenile individuals under the pleon. Both species are sympatric, but Paranaxia keesingi sp. nov. is found in deeper waters than P. serpulifera.

Trevathana noae, a new species of coral inhabiting barnacle (Cirripedia: Thoracica: Pyrgomatidae).

We describe a new species from the genus Trevathana Anderson, 1992, collected from the Cocos/Keeling Islands in the Indian Ocean. Trevathana noae sp. nov. is similar to other species of Trevathana by its external shell and opercular valve morphology. It is distinct from congeners in that the tergum has a distinct spur which lacks an internal tooth in adult specimens. A key to the known species of Trevathana is given.