Systematic relationships of Chinese freshwater semisulcospirids (Gastropoda, Cerithioidea) revealed by mitochondrial sequences

A new species of freshwater snail of Fenouilia (Gastropoda, Pomatiopsidae) from northern Guangxi, China, based on morphological and DNA evidence

A new species of pomatiopsid freshwater snail, Fenouiliaundata Chen & He, sp. nov., is described from Guangxi, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: shell with low, prosocline, rounded axial ribs and fine spiral striae, broader than high; aperture broader than shell height; radula with lateral teeth have only two or three faint, wavy ridges on inner side. A molecular analysis of partial mitochondrial COI and 16S DNA sequences supports the systematic position of the new taxon.

The mitochondrial genome of Huaaristarchorum (Heude, 1889) (Gastropoda, Cerithioidea, Semisulcospiridae) and its phylogenetic implications

Research on complete mitochondrial genomes can help in understanding the molecular evolution and phylogenetic relationships of various species. In this study, the complete mitogenome of Huaaristarchorum was characterized to supplement the limited mitogenomic information on the genus Hua. Three distinct assembly methods, GetOrganelle, NovoPlasty and SPAdes, were used to ensure reliable assembly. The 15,691 bp mitogenome contains 37 genes and an AT-rich region. Notably, the cytochrome c oxidase subunit I (COX1) gene, commonly used for species identification, appears to be slow-evolving and less variable, which may suggest the inclusion of rapidly evolving genes (NADH dehydrogenase subunit 6 [ND6] or NADH dehydrogenase subunit 2 [ND2]) as markers in diagnostic, detection, and population genetic studies of Cerithioidea. Moreover, we identified the unreliability of annotations (e.g., the absence of annotations for NADH dehydrogenase subunit 4L [ND4L] in NC_037771) and potential misidentifications (NC_023364) in public databases, which indicate that data from public databases should be manually curated in future research. Phylogenetic analyses of Cerithioidea based on different datasets generated identical trees using maximum likelihood and Bayesian inference methods. The results confirm that Semisulcospiridae is closely related to Pleuroceridae. The sequences of Semisulcospiridae clustered into three clades, of which H.aristarchorum is one; H.aristarchorum is sister to the other two clades. The findings of this study will contribute to a better understanding of the characteristics of the H.aristarchorum mitogenome and the phylogenetic relationships of Semisulcospiridae. The inclusion of further mitochondrial genome sequences will improve knowledge of the phylogeny and origin of Cerithioidea.

Description of a New Species of Hua (Gastropoda: Semisulcospiridae) from Guizhou, China, Based on Morphology and Molecular Evidence

A new species of Hua, Hua qiannanensis sp. nov., is described from Guizhou Province, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: the smooth shell, only three smaller cusps of lateral teeth on the inner side, outer marginal teeth with eight flattened and rounded denticles, an ovipositor pore in females, and BW/H ≥ 80%, B/H = 76.8-82.3%. Molecular analysis based on partial mitochondrial COI and 16S rDNA also supports the systematic position of the new taxon.

Systematic revision of the Japanese freshwater snail

Semisulcospira is a freshwater snail genus highly divergent in the ancient Lake Biwa, Japan, with a history of ~4 million years. Although the shell morphology, karyotype and molecular phylogeny of the genus have been well studied, the systematic status of several non-monophyletic species remains uncertain. In this study, we have evaluated the taxonomic accounts of the species previously identified as Semisulcospira decipiens, S. habei and relatives. We examined the genetic relationships using genome-wide SNP data and elucidated morphological variation among these using Random Forest classification. Morphological relationships between the name-bearing type of S. decipiens and the newly collected specimens were also evaluated. Morphological characteristics effectively discriminated between the nine genetic clusters, and the correlation among morphology and substrates was elucidated. We revised taxonomic accounts of S. decipiens, S. habei, S. arenicola, S. nakasekoae and S. ourensis and synonymised S. multigranosa, S. habei yamaguchi, S. dilatata under S. decipiens and S. fluvialis under S. nakasekoae. We also described two new species, Semisulcospira elongata sp. nov. and Semisulcospira cryptica sp. nov., and redefined two phylogroups of the lacustrine species as the Semisulcospira niponica-group and the Semisulcospira nakasekoae-group. Traits of the species examined exhibiting intraspecific variation in the different substrates and flow velocity may indicate the morphological and trophic adaptations. The habitat-related variation has certainly caused the taxonomic confusion of the lacustrine species. Lake drainage contributes to increasing the species diversity of the genus, generating ecological isolation between the riverine and lacustrine habitats. ZooBank: urn:lsid:zoobank.org:pub:A83B99F4-8709-4295-86B3-A6C595D65DA0

Revisiting a 135-year-old Taxonomic Account of the Freshwater Snail Semisulcospira multigranosa: Designating its Lectotype and Describing a New Species of the genus (Mollusca: Gastropoda: Semisulcospiridae)

The type series of Semisulcospira multigranosa Boettger, 1886 was found in the Malacological Collection at the Senckenberg Naturmuseum for the first time ca. 135 years after its original description. The syntypes consisted of 38 specimens that can be classified into four species. The examination of adult shell morphology of these original materials revealed that the current taxonomic account of S. multigranosa should be amended. Therefore, we designate a lectotype for S. multigranosa, and thus describe S. multigranosa auct. as Semisulcospira davisi sp. nov. Semisulcospira davisi can be discriminated from the other congeners by the characteristics of adult and embryonic shells, and radulae morphology. The present study resolves one of the fundamental taxonomic problems remaining in Semisulcospira snails.