Freshwater mussels of the family Unionidae are a diverse and ecologically significant group in aquatic ecosystems. We sequenced the maternal mitochondrial genomes of eight putative species of the East Asian endemic subtribe Cristariina and, by integrating molecular data and morphological characteristics, described a new genus and species, Acudonta baitiaoensis, and one newly recorded species for China (Cristaria truncata). Integrative taxonomy revealed three new synonyms of Anemina arcaeformis and using mitochondrial phylogenomics we clarified the intergeneric relationships within the subtribe. (Image credit: Lili Liu.)

The conoidean family Raphitomidae is arguably among the most diverse deep-sea gastropod groups. We studied recently collected deep-water raphitomids from south-eastern Australia, generated combined genetic, shell, anatomy and distribution data, described three new species, and revised eight more across several raphitomid genera. Our results contribute to the understanding of the global distributional patterns of deep-sea raphitomid species, ranging from the very rare and possibly endemic to those exhibiting transoceanic ranges or occupying remarkably wide depth intervals. (Image credit: Francesco Criscione.)

Annelids are increasingly being found to comprise a substantial fraction of cryptic biodiversity. Perinereis cultrifera is commonly used as a model species, but the possibility of unreported and undescribed cryptic species may compromise the accuracy and interpretation of results. In this study, integrative taxonomy revealed overlooked morphological traits and 18 different European Perinereis lineages (13 of which are formally described) yielding new molecular and taxonomic data available to a range of efforts including metabarcoding, species identification, conservation and biomonitoring. (Image credit: Joachim Langeneck.)

The diversity and phylogeny of deep-sea Delectopecten scallops are poorly known. We describe Delectopecten thermus sp. nov. from the Higashi–Ensei vent field through morphological, mitogenomic and phylogenetic analyses. Our findings indicate that Delectopecten is monophyletic representing an early diverging pectinid clade, with significant gene-order divergences in mitogenome, but asymbiotic with chemoautotrophs. These results enhance our understanding of the biodiversity of Delectopecten, clarify the phylogenetic relationships within the genus, and provide insights into the trophic patterns of deep-sea scallops. (Image credit: Yi-Tao Lin.)

Phylogenetic relationships within Symphrasinae and between mantispoid subfamilies are poorly understood because of the evolutionary influence of raptorial feeding on morphology. The raptorial condition has been interpreted as a synapomorphy of Raptoneuroptera or a homoplasy of Berothidae and Rhachiberothidae. Phylogenetic affinities of Symphrasinae are investigated using 3 genes and 72 newly interpreted morphological characters. We found support for monophyly of Raptoneuroptera, with Rhachiberothidae and Mantispidae as sister groups, and Symphrasinae (Rhachiberothidae) comprising Anchieta as sister to Trichoscelia + Plega.

The arachnid order Uropygi has never been subjected to phylogenetic research. We perform the first systematic revision and molecular phylogenetic analysis of Uropygi, focusing on the Brazilian genera Thelyphonellus and Mastigoproctus. Our study indicates that Mastigoproctus actually comprises two different genera: the revalidated genus Amauromastigon with a single species, and a new genus Heptatarsus with two species, increasing the number of Brazilian uropygid genera to three. Additionally, we identify ontogenetically variable morphological characters and caution their use in uropygid systematics. (Image credit: Daniel Castro-Pereira.)

Here, we present the results of the first phylogenetic and biogeographical analysis of the marine littoral Adota on the Pacific coasts of the Northern Hemisphere. The biogeographic patterns were compared with those of different lineages of aleocharine beetles with different microhabitats. Reconstructions of the ancestral areas suggest that the common ancestor of Adota occurred widely along the East Asian coasts. Both dispersal and vicariance were important in shaping the current distribution. (Image credit: Jong-Keun Jung and Kee-Jeong Ahn.)

The maternal mitochondrial genomes of Unio szechenyii, Cuneopsis kiangsiensis, Middendorffinaia mongolica and Pseudocuneopsis wuana are sequenced. The validity of Unio szechenyii, previously considered a synonym of Cuneopsis heudei, is supported by the integration of conchometry, soft-body anatomy and molecular evidence, and a recombination as Cuneopsis szechenyii comb. nov. is proposed. The intrageneric relationships within the genera Cuneopsis and Pseudocuneopsis are elucidated based on the mitochondrial phylogenomics. Middendorffinaia mongolica, a new record for China, is proposed for transfer from the tribe Middendorffinaiini to the tribe Unionini and classification under the subtribe Middendorffinaiina stat. rev. (Image credit: Ruiwen Wu.)

In this study we report two new stygomorphic amphipods, Palearcticarellus hyperboreus sp. nov. and Pseudocrangonyx elgygytgynicus sp. nov., from Lake El’gygytgyn in north-eastern Siberia. Molecular phylogenetic analyses confirm their affinity to Crangonyctidae and Pseudocrangonyctidae, respectively, and reveal that speciation preceded Pleistocene glaciations. Although adapted to subterranean life, these species are found exclusively in surface waters, highlighting Lake El’gygytgyn as a high latitude refugium for ancient pre-glacial fauna and expanding the known distribution of stygomorphic amphipods. (Image credit: Denis Copilaş-Ciocianu and Dmitry Sidorov.)

The epigean and subterranean spider genus Cybaeus is highly species rich in the Japanese Archipelago. The Japanese Cybaeus spiders are classified into ~100 species, but their phylogeny is unclear. We conducted molecular phylogenetic analyses and divergence time estimation based on 73 species and demonstrated that several Cybaeus species should be classified into other genera. Divergence dating suggested that the opening of the Sea of Japan c. 20 million years ago may have promoted diversification and speciation of Japanese cybaeids. (Image credit: Yoh Ihara and Takafumi Nakano.)

Taxonomic identification of spider species from morphological structures has limitations in cases of closely related species or intraspecific variability. We investigate the utility of genetic barcoding with the mitochondrial marker cytochrome c oxidase I (COI) in ghost spiders of the subfamily Amaurobioidinae. Most discrepancies between DNA barcoding and morphological identification are explained by low geographic sampling or by geographically structured lineages. In addition, we show that the marker COI is phylogenetically informative for deeper nodes in the tree. (Image credit: Martín Ramírez.)