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Conspecificity of the morphologically-similar, sympatric nudibranch species Dendrodoris gunnamatta (Allen, 1932) and Dendrodoris krusensternii (Gray, 1850) was tested using sequences of the mitochondrial COI gene. Data analysis supports the presence of phenotypic polymorphy in D. krusensternii where specimens from large estuaries and embayments in central New South Wales, Australia either lack or have highly reduced sky-blue ocellae.

A recent taxonomic revision split the circumglobal sea hare Aplysia parvula into 10 constituent taxa, of which only three are likely to be found in the Southern Pacific. This prompted an investigation of animals previously identified as A. parvula from Australia. Specimens collected from Eastern Australia and Hunter Island, east of New Caledonia, could not be satisfactorily identified with any of the currently accepted taxa based on morphological diagnostic features listed in the revision, however, the presence of a highly concave shell is diagnostic. Quantification of genetic divergence using Cytochrome Oxidase I (COI) supports the delineation of this species as a distinct taxon, and a phylogenetic reconstruction based on concatenated COI, 16S and H3 markers reveals a sister relationship with the newly described Aplysia ghanimii from the Atlantic and Western Indian Oceans and an undescribed species from Japan. As a result, the name Aplysia concava G. B. Sowerby, I, 1833 is resurrected for this species. As the original description was based solely on a shell, a redescription is provided here with photographs of living animals and microscope images of internal anatomical structures.

During abundance surveys of the nine-armed sea star Luidia senegalensis (Lamark, 1816) in shallow waters north of Cubagua Island, Venezuela, novel locomotive behaviour was recorded in one sea star. The animal was observed to ‘walk’ with four arms in contact with the benthos whilst the remaining five were held erect. This previously unreported means of locomotion may be: for chemosensory detection of the surroundings; to alter the characteristic track pattern left in sediments as a means to avoid detection by predators; or, to lift the arms to attract commensal cleaners, thus eliminating epibiont commensals that may occupy the ambulacral groove. Whilst the predators of L. senegalensis remain unknown, earlier observations of serranid fish biting this species may support the notion of this behaviour as a predator avoidance strategy.

Assemblages of heterobranch sea slugs are notoriously variable in space and time which has sometimes led to their exclusion from broader studies of patterns of biodiversity. This variability may also result in a failure to detect underlying spatial and temporal patterns. Assemblage data (species abundances) from three intertidal sites over a period of 13 months, were used to compare the conclusions drawn from three different analytical approaches—a non-specific test for differences among months, and tests of cyclicity, and seriation, using specific model matrices. While no significant difference was detected for the non-specific test (i.e. concluding no significant temporal variation), the data were significantly correlated to both model matrices with the cyclicity model outperforming the seriation model at two of the three sites. The study also highlighted the spatial variability of assemblages over a scale of just a few kilometres. Wider testing using previously published datasets confirmed the ...

The Australian heterobranch sea slugs are popular among the public and are also important as potential indicators of environmental change. Despite this, there is no simple key for their id...

The aplysiid sea hare, Syphonota geographica has a predominantly circumtropical distribution. Over the last 15 years, it has spread throughout the eastern Mediterranean Sea where it is reg...

The south eastern Australian coast is a recognised climate change hot spot and, as a result, poleward shifts in distribution are expected for many taxa. Between March 2015 and January 2016, we observed seven species of sea slug south of their previously recorded range. Each species has

Port Stephens, a large natural harbour on the central New South Wales (NSW) coast, provides ideal oceanographic and benthic conditions for the growth of marine algae and seagrasses, and this promotes a suite of herbivorous heterobranch sea slugs such as sea hares and sap-sucking sea slugs. In this article we document both historic and recent observations of sea hares (family Aplysiidae) from Port Stephens with the intention of recording species diversity. The western South Pacific region has the richest aplysiid fauna in the world, with 16 species now recorded in Port Stephens. This location is the most taxonomically diverse for this family in Australia. Despite this hotspot of aplysiid diversity, the taxonomy and nomenclature of 12 species is uncertain, a fact highlighted by a series of nomenclatural notes included in this article. We herein report the first observation of Petalifera sp. in Australian waters. Dolabrifera jacksoniensis Pilsbry, 1896 is newly synonymised with D. brazieri G.B. Sower...

The small, green sea hare, Phyllaplysia viridis, originally described from Indonesia in 1905, has rarely been recorded since. Because the taxonomic status of Phyllaplysia is uncertain, there remains a need for clarification of the currently accepted species. To do so, we used contemporary specimens from eastern Australia and Indonesia to redescribe P. viridis using photographs and scanning electron imagery of its external and internal morphology. Although all examined specimens were small, consistently green animals, images revealed some variation in colour and pattern among adults. Molecular data confirmed the presence of P. viridis in the Philippines, Indonesia and eastern Australia. A phylogenetic tree based on available COI barcode sequences illustrate a sister relationship with other Phyllaplysia. The construction of a haplotype network failed to show any marked geographic structure among specimens.

There is increasing evidence of poleward migration of a broad range of taxa under the influence of a warming ocean. However, patchy research effort, the lack of pre-existing baseline data, and taxonomic uncertainty for some taxa means that unambiguous interpretation of observations is often difficult. Here, we propose that heterobranch sea slugs provide a useful target group for monitoring shifts in distribution. As many sea slugs are highly colourful, popular with underwater photographers and rock-pool ramblers, and found in accessible habitats, they provide an ideal target for citizen scientist programs, such as the Sea Slug Census. This maximises our ability to rapidly gain usable diversity and distributional data. Here, we review records of recent range extensions by tropical species into the subtropical and temperate waters of eastern Australia and document, for the first time in Australian waters, observations of three tropical species of sea slug as well as range extensions for a further six to various locations in the Tasman Sea.

The distribution of heterobranch sea slugs is generally poorly documented at a regional scale. Thus, it is currently difficult to quantify biodiversity, identify endemic and invasive species, and track range shifts at scales relevant to conservation management. For Lord Howe Island, which lies ~600 km east of the New South Wales (NSW) mid-north coast, data from a range of taxa indicate high biodiversity and endemism, but this has not been examined for heterobranch sea slugs. To address this deficit, we collated occurrence data on sea slugs from both private and public sources, including museum records, scientific literature, field guides and citizen science activities. A total of 186 nominal (formally described) species in 82 genera and 31 families were identified from intertidal and subtidal habitats. Of these, two species are endemic to Lord Howe Island, two have not been recorded elsewhere in Australia, and 28 have not been recorded on the mainland coast of NSW. These results support studies of other taxa suggesting that the relative isolation of the island has facilitated the development of diverse and unique assemblages. However, this isolation is moderated by larval transport from surrounding regions, resulting in considerable overlap of the species pool with the mainland coast of NSW and tropical areas to the north.

Port Stephens, on the central New South Wales coast, provides ideal oceanographic and benthic conditions for the settlement and growth of larvae of tropical species delivered from the north by the East Australian Current. The popularity of the bay for recreational and scientific diving has facilitated extensive documentation of the biota over several decades, confirming its high biodiversity. Of the 313 species of heterobranch sea slugs recorded from Port Stephens to date, 30 are not known to occur further south. Our observations increase the number of taxa with a southern distribution limit at Port Stephens by 12 species and add to a growing list of marine taxa that are progressively extending their southern range, potentially as a result of climate change.

Southern range extensions of the tropical Australian heterobranch sea slug fauna may be symptomatic of climate change, particularly in south-eastern Australia, a recognized climate change hot-spot. In the Solitary Islands Marine Park, northern New South Wales, the presence of biogeographic mixing means that the southern coastal distribution limit of several tropical marine species and the northern limit of some temperate species overlap. During a year-long series of monthly surveys of sea slug communities on intertidal rocky shores, we observed four species beyond their previously recorded range – Colpodaspis thompsoni, Elysia pusilla, Phidiana bourailli and Herviella claror. The southern migration of species is an anticipated response to warming seas and we note an apparent extension of the southern limit for these taxa.

The southwest coast of Western Australia is heavily influenced by the south-flowing Leeuwin Current. In summer, the current shifts and the north-flowing Capes Current delivers water from the south to nearshore environments and with it a supply of larvae from cooler waters. The nudibranch Tenellia catachroma (Burn, 1963) was considered restricted to Victorian waters; however, its discovery in eastern South Australia in 2013 revealed its capacity to expand its range west. In March 2017 a single individual was observed in shallow subtidal waters at Cape Peron, Western Australia, some 2000 km to the west of its previous range limit. Moreover, its distribution has extended northwards, possibly aided by the Capes Current, into a location of warming. This observation significantly increases the range for this Victorian emigrant to encompass most of the southern Australian coast, and also represents an equatorward shift at a time when the reverse is expected.

Although the Indo-Pacific is the global centre of diversity for the heterobranch sea slugs, their distribution remains, in many places, largely unknown. On the Australian east coast, their diversity decreases from approximately 1000 species in the northern Great Barrier Reef to fewer than 400 in Bass Strait. While occurrence records for some of the more populated sections of the coast are well known, data are patchy for more remote areas. Many species have very short lifecycles, so they can respond rapidly to changes in environmental conditions. The New South Wales coast is a recognised climate change hot-spot and southward shifts in distribution have already been documented for several species. However, thorough documentation of present distributions is an essential prerequisite for identifying further range extensions. While distribution data are available in the public realm, much is also held privately as photographic collections, diaries and logs. This paper consolidates the current occurrence data from both private and public sources as part of a broader study of sea slug distribution in south-eastern Australia and provides an inventory by region. A total of 382 species, 155 genera and 54 families is reported from the mainland coast of New South Wales.