On the identities of the sesarmid crabs, Sesarma villosum A. Milne-Edwards, 1869, and Clistocoeloma suvaense Edmondson, 1951, with the description of a new species from the West Pacific (Decapoda, Brachyura, Thoracotremata).

The identities of two sesarmid crabs, Clistocoeloma villosum (A. Milne-Edwards, 1869), and C. suvaense Edmondson, 1951, both currently in Clistocoeloma A. Milne-Edwards, 1873, are poorly known and the types have not been studied in detail since their description. Clistocoeloma villosum, supposedly widespread, has been recorded from Madagascar and East Africa to Singapore, Japan, Korea, and Samoa. Clistocoeloma suvaense is only known for certain from one male collected from its type locality, Fiji. The taxonomy of C. villosum, and C. suvaense is clarified on the basis of the type specimens from Samoa and Fiji, respectively. A new species, which has long been confused with C. villosum, is described from Southeast Asia and Western Pacific.

Redescription of Pseudograpsus intermedius Chhapgar, 1955 (Decapoda, Brachyura, Varunidae) from India.

The identity of Pseudograpsus intermedius Chhapgar, 1955 (Varunidae), a crab species found in mangrove habitats of India is clarified. The re-examination of the holotype male and examination of fresh specimens collected from Goa State, India, revealed that P. intermedius shows significant morphological differences from the generic characters of Pseudograpsus. As such, a new genus Chhapgarus n. gen. is established for the species.

Chromosome-level genome assembly of Paralithodes platypus provides insights into evolution and adaptation of king crabs.

The blue king crab, Paralithodes platypus, which belongs to the family Lithodidae, is a commercially and ecologically important species. However, a high-quality reference genome for the king crab has not yet been reported. Here, we assembled the first chromosome-level blue king crab genome, which contains 104 chromosomes and an N50 length of 51.15 Mb. Furthermore, we determined that the large genome size can be attributed to the insertion of long interspersed nuclear elements and long tandem repeats. Genome assembly assessment showed that 96.54% of the assembled transcripts could be aligned to the assembled genome. Phylogenetic analysis showed the blue king crab to have a close relationship with the Eubrachyura crabs, from which it diverged 272.5 million years ago. Population history analyses indicated that the effective population of the blue king crab declined sharply and then gradually increased from the Cretaceous and Neogene periods, respectively. Furthermore, gene families related to developmental pathways, steroid and thyroid hormone synthesis, and inflammatory regulation were expanded in the genome, suggesting that these genes contributed substantially to the environmental adaptation and unique body plan evolution of the blue king crab. The high-quality reference genome reported here provides a solid molecular basis for further study of the blue king crab's development and environmental adaptation.

Responses of urban reef corals during the 2016 mass bleaching event.

Predicting the bleaching responses of corals is crucial in light of frequent heat stress events to manage further losses of biodiversity and ecosystem functioning, especially for reefs impacted by urbanisation. We examined if the coral cover and community at various Singapore sites changed during the 2016 global coral bleaching event. Bleaching prevalence varied widely among sites in June 2016, and was best explained by site and coral species. While some sites were minimally impacted, others registered significant decreases in coral cover and community changes persisting till March 2017, when normal colouration was mostly regained by corals. Bleaching susceptibility was associated with larger corallites in hermaphrodites and smaller corallites in gonochores (probably due to the cost of maintaining dual sexual functions in hermaphrodites), and with increasing proximity between polyps (likely because thermal damage would be less contained among polyps with greater physiological integration). However, bleaching resilience-the capacity to regain baseline pigmentation-was poorly explained by the traits studied. Our findings suggest that the interplay between local conditions and species composition strongly affects bleaching outcomes on urbanised reefs, and underscore the utility of coral traits for predicting bleaching responses to help in formulating appropriate management strategies.

The identities of three species of Parahelice Sakai, Türkay amp; Yang, 2006 (Crustacea: Brachyura: Varunidae) from the western Pacific, based on morphological and molecular evidence.

Species of the varunid genus Parahelice Sakai, Türkay Yang, 2006, inhabit high intertidal areas of oceanic islands of the tropical Indo-West Pacific region. As several species of Parahelice and Pseudohelice subquadrata (Dana, 1851) were found to be sympatric in some places, and their morphological differences are minor, especially in females, the misidentification of species is not uncommon in the literature. In this study, the DNA barcoding marker, mitochondrial cytochrome c oxidase subunit I (COI), was applied to confirm species identities and this was correlated with the specific characters of males and females. Distributions of three species of Parahelice were also updated, with Par. daviei (Sakai, Türkay Yang, 2006), Par. pilimana (A. Milne-Edwards, 1873), and Par. pilosa (Sakai, Türkay Yang, 2006) being new records to Taiwan, and Par. pilosa new to Bali, Indonesia.

Review of the mudflat varunid crab genus Metaplax (Crustacea, Brachyura, Varunidae) from East Asia and northern Vietnam.

Intertidal mudflat crabs of the genus Metaplax H. Milne Edwards, 1852 (Crustacea: Brachyura: Varunidae) from China, Taiwan, and northern Vietnam are taxonomically revised by morphological and molecular evidence. These crabs show sexual dimorphism and morphological variation of a considerable range in the infraorbital ridge, one of the primary features previously used for species identification. In this study, four species were identified from the region: M. elegans De Man, 1888; M. longipes Stimpson, 1858; M. sheni Gordon, 1930; and M. tredecim Tweedie, 1950. Based on the results of the morphological examination, and as confirmed by molecular evidence from mitochondrial cytochrome oxidase subunit I (COI), taxonomic confusion surrounding M. longipes was resolved, and M. takahasii Sakai, 1939, is considered a junior synonym of M. longipes. The geographical distribution of Metaplax longipes extends along the shores of China, north to Jiangsu, whereas the Southeast Asian M. tredecim was newly recorded from northern Vietnam and Hong Kong.

Helice epicure, A New Species of Varunid Mud Crab (Brachyura, Decapoda, Grapsoidea) from the Ryukyus, Japan.

Ngan Kee Ng, Tohru Naruse, and Hsi-Te Shih (2018) Helice epicure, a new species of varunid crab, is described from the Ryukyu Islands, Japan. The new species in the genus Helice De Haan, 1833 can be distinguished from its congeners by morphological differences in the chelae and suborbital crenulation. The morphological differences between the new species and a sister clade (the H. latimera complex, including H. latimera Parisi, 1918, H. tientsinensis Rathbun, 1931 and H. formosensis Rathbun, 1931) are supported by mitochondrial cytochrome oxidase subunit I (COI) divergences. However, the phylogenetic relationship within the H. latimera complex is unresolved for the time being.