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Accurate taxonomy and descriptions of species are key to understanding biodiversity. The echinoid genus Tripneustes is an ecologically and commercially important taxon that includes the tropical Tripneustes gratilla gratilla and the recently described T. kermadecensis from Australia and New Zealand. While examining the Australian Museum collections to clarify the distributions of these two species in eastern Australia we found potential senior type material for T. kermadecensis. These specimens from Sydney Harbour were originally described in 1878 as Evechinus australiae by Tenison-Woods but neither illustrated nor redescribed in any subsequent report. We undertook molecular and morphological analysis of these specimens to determine whether T. kermadecensis and E. australiae represent two distinct taxa or not. This included micro-computed tomography, quantification of test traits and molecular genetic analysis. The COI sequence and morphology of Evechinus australiae matched that of Tripneustes kermadecensis. As such, T. kermadecensis is a junior synonym of Evechinus australiae. The correct designation of this taxon is therefore Tripneustes australiae (Tenison-Woods, 1878). [ABSTRACT FROM AUTHOR]

The diversity and distribution of marine species in eastern Australia is influenced by one of the world's strongest western boundary currents, the East Australia Current, which propels water and propagules poleward, a flow intensifying due to climate change.Population genetic structure of the asterinid sea star Meridiastra calcar was investigated across its range in eastern Australia (12° of latitude, 2,500 km) from northern New South Wales to its poleward‐extending range in Tasmania at the southern edge influence of the East Australia Current.Population structure and connectivity of M. calcar were examined across six bioregions using six microsatellite loci (nuclear DNA) and the control region (mitochondrial DNA). The potential influence of the extent of M. calcar's intertidal rock platform habitat was also assessed.Genetic structure analysis indicated that the Hawkesbury Shelf contained distinct genetic clusters, whereas the two sites in the Batemans Shelf differed from each other, with Jervis Bay Marine Park having just one genetic cluster. The Manning Shelf, Twofold Shelf, and Bruny bioregions all had similar genetic composition.Strong self‐seeding (68–98%) was indicated by microsatellite loci for all bioregions, with lower (0.3–6.5%) migration between bioregions. Poleward (New South Wales to Tasmania) migration was low except from the Manning Shelf (30%).Contemporary population connectivity and genetic structure of M. calcar appear to be influenced by ocean currents, habitat distribution, and its short planktonic larval duration, which was a minimum of 12–14 days, depending on availability of a settlement cue.The dominance of unique genetic groups in the Hawkesbury bioregion shows the importance of this region for M. calcar and possibly a diversity of co‐distributed rock platform species. This highlights how important it is to have a large marine park in the Hawkesbury bioregion, which is presently lacking. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) driven by sea water uptake of anthropogenic atmospheric CO 2 has broad deleterious effects on marine species including modified behavioural interactions such as between predators and prey. Predatory sea stars are key species in many marine ecosystems and often elicit defensive responses in their prey. This study investigated the effect of elevated CO 2 on the escape response of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar. In response to touch by M. calcar , P. exigua exhibits a distinct fleeing response. The escape response of P. exigua with respect to velocity and escape trajectory was investigated after both species were acclimated in OA conditions. At pH T 7.6 and 7.8 velocity and escape trajectory of the fleeing response of P. exigua did not differ from that seen in the ambient treatment. However, there was a delay in the time that P. exigua started to flee with the initiation time being 2.8 times slower (10 vs 28 s) at pH T 7.6. This delay may increase the vulnerability of P. exigua to predation by M. calcar and have ecological effects with respect to the role of this species as an algal grazer on rocky shores of southeast Australia where these sea star species co-occur. • This is the first study to examine the effect of OA on a prey species of seastar. • The escape response of the seastar Parvulastra exigua is delayed in response to OA. • The trajectory of escape away from the predator was not impacted by OA. [ABSTRACT FROM AUTHOR]

The ophiuroid fauna of the le Amsterdam and le Saint-Paul territories (SPA) is reviewed. Four new species are described: Ophiolebes felli, Ophiolebes paulensis, Ophiocomina arnaudi and Amphiura remota. Recent phylogenetic results required a partial reorganisation of Ophiacanthidae and Amphiuridae genera, including the transfer of some Ophiacantha and Ophiomitrella species to a new genus Ophiosabine (O. rosea, O. anomala, O. aristata, O. cuspidata, O. densispina, O. nodosa, O. notata, O. parcita, O. pentactis, O. vivipara, O. wolfarntzi) and existing genera Ophiosemnotes (O. conferta, O. ingrata, O. corynephora, O. clavigera, O. hamata) and Ophiolebes (O. yaldwyni), Ophiacantha spectabilis to Ophiotreta in the Ophiotomidae, and some Amphioplus species to Amphiura (A, acutus, A. ctenacantha, A. cipus). The combination Ophiophycis nixastrum is restored. The SPA endemic species Ophiocten lymani and Amphiura brevispina, and the southern Australian/New Zealand species Ophiactis cuspidata and Ophiocten australis, are recognised as valid species. The North Atlantic species Ophiura ljungmani, Ophiacantha veterna, Ophiosabine cuspidata, Ophiolimna bairdi and Ophiactis nidarosiensis are recorded from the southern Indian Ocean. Shallow water specimens of Ophiura ljungmani from the Western Atlantic are re-identified as O. fallax and O. acervata. The monotypic Ophiothauma heptactis from northern Australia is synonymised with Ophiocomella sexradia and thus the genus Ophiothauma with Ophiocomella. The biogeography of the ophiuroid fauna reflects the position of the islands near the eastward-flowing currents of the South Indian Ocean gyre. The closest affinities are with faunas in the SW Indian Ocean and SE Atlantic Ocean. Despite its proximity, no species are shared with the Kerguelen Plateau to the south. The large temperature gradient across the subtropical front between le Saint-Paul and Kerguelen appears to be a distribution limit for littoral and upper bathyal invertebrates.

Ocean warming and increasing incidence of marine heat waves (MHW) are having far-reaching impacts on coastal ecosystems. The small intertidal asterinid starfish, Parvulastra exigua, in south-eastern Australia, occurs in a global warming hotspot. Development occurs in the intertidal as this species lays eggs and has benthic larvae. The impact of temperature on development to the juvenile was determined over a broad temperature range (12–28 °C) encompassing temperatures experienced during the breeding season (16–20 °C) and cool (- 4 °C) and warm (+10 °C) extremes with the higher temperatures (24–28 °C) simulating a MHW. As the larva to juvenile transition involves major body reorganisation, we determined the impact of temperature on metamorphosis and formation of the normal five-armed juvenile. Development was faster at the higher temperatures 24–28 °C, but survival decreased from 1 to 5 days post fertilisation (dpf). Mortality was evident from day 15 at 22 °C and no larvae survived to 20 dpf at 28 °C. Thermal tolerance decreased over developmental time and the thermal optimum for 95% survival to the 20 day old juvenile spanned from 12 to 20.0 °C with the lethal temperature for 50% survival being 23.5 °C (5.5 °C above ambient). Juveniles reared in 26 °C were smaller, suggesting application of the temperature size rule. Increased temperature (22–26 °C) perturbed pentamery with three, four, six and no-armed juveniles present, contrasting with the low level of non-pentamerous individuals (<3%) in the cooler cultures and in nature (five populations surveyed). Despite the high thermal tolerance in premetamorphic stages, negative carry over effects were evident in the juveniles. This shows the importance of considering the whole of development in climate warming studies. As sea surface temperatures increase and heatwaves become more prevalent, habitat warming will be detrimental to P. exigua populations. • Parvulastra exigua develop on the intertidal in a global warming hotspot. • Thermal optima were representative of current and up to 2 °C above ambient. • Smaller juveniles in warm treatments suggests the temperature size rule. • Pentamery of juveniles was perturbed in warm treatments. • Habitat warming will be detrimental to P. exigua populations. [ABSTRACT FROM AUTHOR]

The Umagillidae Wahl, represent a group of endosymbiotic Platyhelminthes which inhabit two disparate invertebrate host groups, the echinoderms and sipunculans. Sipunculan-inhabiting umagillids are morphologically distinct from those inhabiting echinoderms and have traditionally been placed in a distinct genus and subfamily, Collastoma Dörler, and the Collastominae Wahl, respectively. Although molecular data are available for umagillid species inhabiting echinoids and holothurians, species inhabiting sipunculans have yet to be evaluated with molecular data. Collastoma esotericum n. sp. from the sipunculan Phascolosoma scolops (Selenka & de Man) collected in Moreton Bay, southeast Queensland, Australia, is described. Phylogenetic analyses based on 18S rRNA gene sequences placed C. esotericum in a clade with species of the Umagillidae and the Provorticinae Luther, with strong support. However, within this clade the relationship of C. esotericum to the Umagillidae and Provorticinae was not resolved.

The ophiuroid species listed were collected by benthic faunal surveys from 2016 to 2018 in submarine caves of the Ryukyu Islands, southwestern Japan. The material includes 20 species from 8 families, Amphiuridae, Ophiocomidae, Ophiodermatidae, Ophiolepididae, Ophioleucidae, Ophiomyxidae, Ophionereididae and Ophiotrichidae. This is the first comprehensive report of submarine cave-dwelling ophiuroids from Japanese waters. Also provided is a redescription of a rare species, Dougaloplus echinatus (Ljungman, 1867), with a detailed description of its ossicle morphology. The species has previously been reported from Brazil, Australia, Eastern Indian Ocean to Southern China, in 11-118 m depth, and this is the first record of D. echinatus from Japanese waters. A brief discussion of the scarcity of submarine cave systems, and the need for their conservation, is provided.

Here we use synchrotron radiation-based micro-computed tomography (SRµCT) images of type specimens to confidently place Cassidulus malayanus in a new genus (Kassandrina gen. nov.) that would not have been discovered with traditional techniques, and to describe a new species of Cassidulus (Cassidulus briareus sp. nov.) from Australia and designate a neotype for Cassidulus caribaearum. We also provide remarks describing the taxonomic history of each taxon and a diagnostic table of all living cassidulid species, and extend the known geographic and bathymetric range of C. caribaearum and C. malayanus. Besides rendering novel morphological data, the SRµCT images provide significant insights in the evolution of bourrelets of these cassiduloid echinoids.