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BackgroundCommon seadragons (Phyllopteryx taeniolatus, Syngnathidae) are an emblem of the diverse endemic fauna of Australia's southern rocky reefs, the newly recognized "Great Southern Reef." A lack of assessments spanning this global biodiversity hotspot in its entirety is currently hampering an understanding of the factors that have contributed to its diversity. The common seadragon has a wide range across Australia's entire temperate south and includes a geogenetic break over a former land bridge, which has called its status as a single species into question. As a popular aquarium display that sells for high prices, common seadragons are also vulnerable to illegal capture.ResultsHere, we provide range-wide nuclear sequences (986 variable Ultraconserved Elements) for 198 individuals and mitochondrial genomes for 140 individuals to assess species status, identify genetic units and their diversity, and trace the source of two poached individuals. Using published data of the other two seadragon species, we found that lineages of common seadragons have diverged relatively recently (

Mimicry of warning signals is common, and can be mutualistic when mimetic species harbour equal levels of defence (Müllerian), or parasitic when mimics are undefended but still gain protection from their resemblance to the model (Batesian). However, whether chemically defended mimics should be similar in terms of toxicity (i.e. causing damage to the consumer) and/or unpalatability (i.e. distasteful to consumer) is unclear and in many studies remains undifferentiated. In this study, we investigated the evolution of visual signals and chemical defences in a putative mimicry ring of nudibranch molluscs. First, we demonstrated that the appearance of a group of red spotted nudibranchs molluscs was similar from the perspective of potential fish predators using visual modelling and pattern analysis. Second, using phylogenetic reconstruction, we demonstrated that this colour pattern has evolved multiple times in distantly related individuals. Third, we showed that these nudibranchs contained different chemical profiles used for defensive purposes. Finally, we demonstrated that although levels of distastefulness towards Palaemon shrimp remained relatively constant between species, toxicity levels towards brine shrimp varied significantly. We highlight the need to disentangle toxicity and taste when considering chemical defences in aposematic and mimetic species, and discuss the implications for aposematic and mimicry signal evolution.

Assessing the enormous diversity of Southern Ocean benthic species and their evolutionary histories is a central task in the era of global climate change. Based on mitochondrial markers, it was recently suggested that the circumpolar giant sea spider Colossendeis megalonyx comprises a complex of at least six cryptic species with mostly small and non-overlapping distribution ranges. Here, we expand the sampling to include over 500 mitochondrial COI sequences of specimens from around the Antarctic. Using multiple species delimitation approaches, the number of distinct mitochondrial OTUs increased from six to 15-20 with our larger dataset. In contrast to earlier studies, many of these clades show almost circumpolar distributions. Additionally, analysis of the nuclear internal transcribed spacer region for a subset of these specimens showed incongruence between nuclear and mitochondrial results. These mito-nuclear discordances suggest that several of the divergent mitochondrial lineages can hybridize and should not be interpreted as cryptic species. Our results suggest survival of C. megalonyx during Pleistocene glaciations in multiple refugia, some of them probably located on the Antarctic shelf, and emphasize the importance of multi-gene datasets to detect the presence of cryptic species, rather than their inference based on mitochondrial data alone.

The chromodorid nudibranch Goniobranchus aureopurpureus (Collingwood, 1881) is characterized by numerous yellow spots on a white mantle that is bordered with purple spots. It is believed to be widely distributed in both the Northern and Southern Hemispheres in the West Pacific, showing color varieties in a more-or-less geographically coherent manner. Chromodoris variata Risbec, 1928 (type locality: New Caledonia) has been considered a synonym. In addition, three, similar-looking congeners have been proposed as synonymous with G. aureopurpureus: G. albopustulosus (Pease, 1860) (type locality: Hawaii), G. alius (Rudman, 1987) (type locality: Tanzania), and G. rufomaculatus (Pease, 1871) (type locality: French Polynesia). To test the synonymies proposed above, we performed maximum-likelihood and Bayesian-inference analyses utilizing partial sequences of the cytochrome c oxidase subunit I (COI) and 16S rRNA genes. The taxon sampling included a specimen of G. aureopurpureus newly collected in Hokkaido, Japan, along with other sequences of Goniobranchus deposited in public databases (31 specimens representing 22 species), including one identified as 'Chromodoris aureopurpurea' from New South Wales, Australia; G. albopustulosus from Hawaii; and two 'Chromodoris rufomaculata' from Guam and the Mariana Islands. Goniobranchus aureopurpureus from Japan and from Australia were sister taxa in the resulting trees but differed from each other by 8.6% in terms of 658-bp COI, suggesting that these two represent closely-related but different biological entities. For the Australian taxon, Goniobranchus cf. variatus comb. nov. is proposed herein. Goniobranchus albopustulosus and G. rufomaculatus were not closely related to the G. aureopurpureus-G. cf. variatus clade, rejecting the hypothesis that they are synonymous with either of these species. However, G. albopustulosus and G. rufomaculatus appeared to comprise a single biological entity, warranting further investigation of this potential synonymy. The placement of the Indian Ocean G. alius also remains to be tested. [ABSTRACT FROM AUTHOR]

An increasing number of Antarctic invertebrate taxa have been revealed as cryptic species complexes following DNA-based assessments. This ultimately necessitates a morphological reassessment to find traits that will help identify these cryptic or pseudocryptic species without the need for sequencing every individual. This work concerns comatulid crinoid echinoderms long considered to represent a single, circum-Antarctic species, Promachocrinus kerguelensis. The first molecular studies sought to distinguish the diversity in the complex and understand the constituent species distributions but stopped short of formal taxonomic assessment. Here, we continued to increase sample representation around the Southern Ocean and sequenced the mitochondrial COI gene for all new specimens, and additional genes for a few representatives. We also elucidated previously unappreciated features, particularly body pigmentation and morphology of the centrodorsal ossicle in an attempt to diagnose some species morphologically and based on DNA data. The species complex within Promachocrinus is here resolved into P. kerguelensis Carpenter, 1879, P. vanhoeffenianus Minckert, 1905, P. joubini Vaney, 1910, P. mawsoni (Clark, 1937) comb. nov. (transferred from Florometra) and four previously unnamed species, P. fragarius sp. nov., P. unruhi sp. nov., P. uskglassi sp. nov. and P. wattsorum sp. nov. Although most species can be distinguished morphologically, several cannot be reliably separated without DNA data. All sequenced species are essentially circum-Antarctic, with the notable exception of P. wattsorum sp. nov. that is restricted to the Prince Edward Islands in the sub-Antarctic Indian Ocean and P. vanhoeffenianus that is only known from the type locality in the Davis Sea. The vast nature of the Antarctic and Southern Ocean ecosystem dictates large scale sampling to understand the full extent of the biodiversity. ZooBank: urn:lsid:zoobank.org:pub:F871CDC8-973B-48CE-8A61-33658D4EB4B1 The Antarctic feather star Promachocrinus kerguelensis arguably comprises several species but taxonomic revision has not been attempted. Here we use DNA data and morphological characters to differentiate the species and formally described those that are new. The species complex was resolved into eight species, four of which are newly described, though not all can be reliably distinguished based on morphology. One of the new species has a restricted distribution, but the remainder appear to be circum-Antarctic. [ABSTRACT FROM AUTHOR]

The discovery of four new Xenoturbella species from deep waters of the eastern Pacific Ocean is reported here. The genus and two nominal species were described from the west coast [...]