Abstract The vetigastropod family Calliotropidae is an important and yet poorly understood component of deep-water benthic communities. In this study, the group is investigated through an integrative approach for the first time, with the aim of resolving its systematics in the Australian deep sea. Analyses of concatenated mitochondrial and nuclear DNA sequences revealed the existence in the region of eight clades, treated as primary species hypotheses (PSHs). Following additional evaluation of shell and radular features, as well as examination of geographic and bathymetric ranges, these PSHs were converted to secondary species hypotheses (SSHs). Our data suggested that Calliotropis and Solaricida represent two well-differentiated genera. Solaricida, here removed from the synonymy of Calliotropis, is distinguished by having an epipodial cylinder. Three species are assigned to Solaricida, one of which is new (Solaricida vorago sp. nov.). In addition, five species of Calliotropis are recognized, one being new (Calliotropis montismarini sp. nov.). Bathybembix abyssorum is transferred to Calliotropis based on its close phylogenetic relationships with other species in this genus. Based on the evidence available, the most likely speciation mechanisms involved are evaluated in the attempt to explain the diversity patterns of calliotropids in Australian deep waters.
Abstract Defining species boundaries challenges taxonomists, particularly for groups with multiple, conflicting, or alternative names. An example is the taxonomy of forest agamid lizards (Gonocephalus) in the Philippines, which have not been comprehensively studied until a multilocus molecular study by Welton et al. (2017) identified 12 distinct lineages. However, the relation of these lineages to known species remains unclear, raising questions about biologically meaningful species-level diversity. Here, we tested the occurrence of 12 lineages using new genomic and morphological data. We recovered a phylogenomic tree similar to that of Welton et al. with at least 12 lineages embedded within two highly supported clades: the northern-central Philippines and the southern Philippines. Species delimitation analyses revealed widespread discordance among lineages within clades, characterised by minimal genomic divergence and high levels of shared ancestry, but no discordance was observed between the two clades. Concordant with phylogenomic results, our morphological analyses consistently identified two diagnosable groups. Examination of name-bearing type specimens clarifies the appropriate assignment of two names (among three available) to the two species delimited here. Our study demonstrates that a long-standing taxonomic issue can be addressed by rigorously integrating all available data and modern tools to support or overturn species hypotheses.
Abstract Elmidae (riffle beetles) mostly inhabit running waters and are well known as ecological indicators. Originating in the Cretaceous, they are one of the most diverse water beetle families on all continents except Antarctica. Elmids exhibit two distinct adult ecomorphotypes, which have shaped higher classification: fully aquatic Elminae and amphibious Larainae. Recent phylogenetic analyses suggested these ecomorphotypes evolved convergently, but were based on relatively few taxa, largely from the Northern Hemisphere. Using an almost complete dataset for Austral Elmidae, and the most extensive for the family, we reveal at least five independent shifts between lifestyle in riffle beetles, including three in the Southern Hemisphere, these apparently being primarily from laraine to elmine ecomorphotype. One South African laraine lineage represents a new genus and species, Dracolara inexpectata gen et sp. nov., which is described here. Our findings highlight the morphological plasticity of riffle beetles and our limited knowledge of southern African freshwater biodiversity.
Abstract Tardigrades are established model organisms in stress biology and are increasingly being explored in ecotoxicology. Here, we use the laboratory-cultured eutardigrade Hypsibius exemplaris to develop a robust and scalable workflow integrating automated low-magnification brightfield imaging in 384-well plates with deep-learning-based phenotype classification. Applying this workflow to 5 day exposures to cadmium(II), mercury(II), and zinc(II) chlorides, we show that H. exemplaris exhibits high tolerance to metal-induced stress compared with other aquatic invertebrates. To our knowledge, this is the first toxicity assessment of mercury and zinc salts in tardigrades and extends the limited existing data on cadmium toxicity.
Abstract The digestive tract of nematodes is divided into several regions with distinct functions. The anterior region contains a muscular-glandular feeding organ that has traditionally been designated either as the oesophagus or as the pharynx. This review examines the historical origin of this dual terminology and evaluates it in the light of anatomical definitions and comparative morphology. The evidence indicates that the coexistence of both terms is largely the result of historical convention rather than anatomical interpretation. The nematode feeding organ shares with the pharynx of other ecdysozoans, particularly cycloneuralians, its position, specialized musculature, glandular organization and role in food ingestion, whereas the oesophagus, when present, is consistently a short conduit connecting the pharynx to the intestine. These observations support the recognition of the nematode feeding organ as a pharynx and the abandonment of the term oesophagus in favour of terminology that is more consistent with current concepts of homology and comparative anatomy.
