The genus Haloa includes dull-coloured species of haminoeid snails inhabiting tidal and shallow waters of the tropical and sub-tropical Indo-West Pacific. This paper reports on the diversity and systematics of Haloa based on the phylogenetic hypothesis generated by Oskars and Malaquias (2019) and on the morphological study of specimens. Shells, external features and anatomical characters from the jaws, radula, gizzard plates and male reproductive system were studied by optical and scanning electron microscopy. The molecular species delimitation method Automatic Barcode Gap Discovery, using DNA sequences of the cytochrome c oxidase subunit I gene, was implemented to aid delimiting candidate species. Thirteen species were recognised as valid, including two new to science, namely Haloa cobbi, sp. nov. and Haloa eora, sp. nov., and one unnamed species herein referred to as Haloa sp. 1. Species depict intraspecific variability in their colouration and little character displacement in their anatomy. Shells are of limited taxonomic use; only details of the male reproductive system (e.g. fundus) and the DNA were truly diagnostic. Three species have an Indo-West Pacific distribution and three are restricted to the Indian Ocean. The remaining seven species occur in the Western and Central Pacific Ocean, three of them having geographical ranges restricted to offshore islands.

Extensive sampling around Martinique during the Muséum National d’Histoire Naturelle ‘Madibenthos’ expedition in 2016 resulted in a collection of hundreds of alpheid shrimps, of which 21 distinct species of Synalpheus Spence Bate, 1888 are studied herein. Combining results of a morphological analysis, a phylogenetic tree (combined 16S and COI) and species delimitation analyses (ABGD and PTP) indicates three species as new to science. These species are S. chaki sp. nov., S. corbariae sp. nov., and S. macdonaldi sp. nov. The first two new species belong to the S. rathbunae Coutière, 1909 species group, whereas the third new species broadly groups with the S. gambarelloides group. Additionally, 13 new country records of Synalpheus are reported for Martinique.

The Antarctic marine environment, although rich in life, is predicted to experience rapid and significant effects from climate change. Despite a revolution in the approaches used to document biodiversity, less than one percent of Antarctic marine invertebrates are represented by DNA barcodes and we are at risk of losing biodiversity before discovery. The ease of sequencing mitochondrial DNA barcodes has promoted this relatively ‘universal’ species identification system across most metazoan phyla and barcode datasets are currently readily used for exploring questions of species-level taxonomy. Here we present the most well-sampled phylogeny of the direct-developing, Southern Ocean nudibranch mollusc, Doris kerguelenensis to date. This study sampled over 1000 new Doris kerguelenensis specimens spanning the Southern Ocean and sequenced the mitochondrial COI gene. Results of a maximum likelihood phylogeny and multiple subsequent species delimitation analyses identified 27 new species in this complex (now 59 in total). Using rarefaction techniques, we infer more species are yet to be discovered. Some species were only collected from southern South America or the sub-Antarctic islands, while at least four species were found spanning the Polar Front. This is contrary to dispersal predictions for species without a larval stage such as Doris kerguelenensis. Our work demonstrates the value of increasing geographic scope in sampling and highlights what could be lost given the current global biodiversity crisis.