We apply rigorous taxonomic and phylogenetic frameworks to shed light on both the taxonomy and evolution of amphidromous freshwater shrimps. Automatic species delineation methods based on molecular data revealed the existence of several species complexes within Macrobrachium. Results suggest habitat-driven speciation modes, where species differentiate in similar habitats distributed across the Indo-Pacific. The morphology of amphidromous Macrobrachium reflects numerous conserved adaptations to flow velocity. (Image credit: Valentin de Mazancourt.)

Heterostigma is a poorly known genus of pyurid ascidian, deemed to inhabit the interstitial space between coarse sand grains. A new species, Heterostigma monniotae, is described, updating the taxonomy of the genus and clarifying its phylogenetic position through analyses of single loci and complete mitochondrial genome. In addition, observations on live specimens revealed an ontogenetic shift in mature specimens from a sessile to a motile phenotype. These new findings shed light on the evolutionary implications of this adaptive strategy. (Image credit: R. Virgili.)

The family Costellariidae is a charismatic, species-rich, yet poorly studied group of marine gastropod molluscs. Recent analyses of DNA sequences and shell features have failed to embrace the complexity of the group. Here, we analyse the morphology, DNA barcodes and genomic data from over 200 species, with emphasis on the South Pacific and Caribbean faunae, describing 9 new genera and 23 new species. Our results update the phylogeny and systematics of Costellariidae, corroborating patterns of species diversity in tropical seas. (Image credit: Alexander Fedosov.)