<i>Bayerotrochus belauensis</i>, a new species of pleurotomariid from the Palau Islands, western Pacific (Gastropoda: Pleurotomariidae)

A new pleurotomariid species, Bayerotrochus belauensis new species, collected from the Palau Islands, western Pacific, is described and illustrated. This new species is most similar in shell morphology to B. teramachii (Kuroda, 1955), from which it may be distinguished by its thinner, lighter shell with a taller, more stepped spire and lack of pronounced spiral sculpture along the shell base. Molecular data (COI) show B. belauensis new species to be more closely related to B. boucheti from New Caledonia and B. delicatus from Yap, than to B. teramachii. Bayerotrochus boucheti (Anseeuw and Poppe, 2001) differs in having a broader, more conical spire, a more depressed aperture, and a more darkly pigmented shell with spiral sculpture on the shell base. The recently described B. delicatus S.-P. Zhang, S.Q. Zhang, and Wei, 2016 is easily distinguished by its much smaller size and distinctive shell profile

The mitogenome of the sunken wood limpet Notocrater youngi: insights into mitogenome evolution in Lepetellida (Gastropoda: Vetigastropoda)

The complete mitochondrial genome of the pseudococculinid limpet Notocrater youngi was determined using Illumina sequencing and found to be a double-stranded circular molecule 15,915 bp in length. It contains the usual 13 protein-coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes, although with a gene order that differs from those of all other presently known Vetigastropoda, and that is derived within Lepetellida. Phylogenetic analyses based on amino acid sequences join the three pseudococculinid species in a clade and confirm the well-supported clade Scissurelloidea + (Lepetelloidea + Lepetodriloidea) but not a monophyletic Lepetellida as currently understood. Patterns of gene order rearrangements are concordant with these findings.JEU was supported by the Peter Buck Postdoctoral Fellowship Program from the Smithsonian Institution (2017–2019) and the Atracción Talento de la Comunidad de Madrid Fellowship Program (REFF 2019-T2/AMB-13166)Peer reviewe

A Phylogenomic Backbone for Gastropod Molluscs

Gastropods have survived several mass extinctions during their evolutionary history resulting in extraordinary diversity in morphology, ecology, and developmental modes, which complicate the reconstruction of a robust phylogeny. Currently, gastropods are divided into six subclasses: Caenogastropoda, Heterobranchia, Neomphaliones, Neritimorpha, Patellogastropoda, and Vetigastropoda. Phylogenetic relationships among these taxa historically lack consensus, despite numerous efforts using morphological and molecular information. We generated sequence data for transcriptomes derived from 12 taxa belonging to clades with little or no prior representation in previous studies in order to infer the deeper cladogenetic events within Gastropoda and, for the first time, infer the position of the deep-sea Neomphaliones using a phylogenomic approach. We explored the impact of missing data, homoplasy, and compositional heterogeneity on the inferred phylogenetic hypotheses. We recovered a highly supported backbone for gastropod relationships that is congruent with morphological and mitogenomic evidence, in which Patellogastropoda, true limpets, are the sister lineage to all other gastropods (Orthogastropoda) which are divided into two main clades 1) Vetigastropoda s.l. (including Pleurotomariida + Neomphaliones) and 2) Neritimorpha + (Caenogastropoda + Heterobranchia). As such, our results support the recognition of five subclasses (or infraclasses) in Gastropoda: Patellogastropoda, Vetigastropoda, Neritimorpha, Caenogastropoda, and Heterobranchia. [Compositional heterogeneity; fast-evolving; long-branch attraction; missing data; Mollusca; phylogenetics; systematic error.]Peer reviewe

The biodiversity of the deep Southern Ocean benthos

Our knowledge of the biodiversity of the Southern Ocean (SO) deep benthos is scarce. In this review, we describe the general biodiversity patterns of meio-, macro- and megafaunal taxa, based on historical and recent expeditions, and against the background of the geological events and phylogenetic relationships that have influenced the biodiversity and evolution of the investigated taxa. The relationship of the fauna to environmental parameters, such as water depth, sediment type, food availability and carbonate solubility, as well as species interrelationships, probably have shaped present-day biodiversity patterns as much as evolution. However, different taxa exhibit different large-scale biodiversity and biogeographic patterns. Moreover, there is rarely any clear relationship of biodiversity pattern with depth, latitude or environmental parameters, such as sediment composition or grain size. Similarities and differences between the SO biodiversity and biodiversity of global oceans are outlined. The high percentage (often more than 90%) of new species in almost all taxa, as well as the high degree of endemism of many groups, may reflect undersampling of the area, and it is likely to decrease as more information is gathered about SO deep-sea biodiversity by future expeditions. Indeed, among certain taxa such as the Foraminifera, close links at the species level are already apparent between deep Weddell Sea faunas and those from similar depths in the North Atlantic and Arctic. With regard to the vertical zonation from the shelf edge into deep water, biodiversity patterns among some taxa in the SO might differ from those in other deep-sea areas, due to the deep Antarctic shelf and the evolution of eurybathy in many species, as well as to deep-water production that can fuel the SO deep sea with freshly produced organic matter derived not only from phytoplankton, but also from ice algae