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Clausiliidae snails have been of great interest to conchologists for their unique clausilium structure and rich species diversity. We described the complete mitochondrial genome of Euphaedusa plano...

Stylommatophora is a main clade of Gastropoda that encompasses approximately 112 gastropod families and may exceed a total of 30,000 species. Twenty-four complete stylommatophoran mitogenomes have been sequenced to date, yet our understanding of mitochondrial evolution in stylommatophorans is still in its infancy. To further expand the set of available mitogenomes, we sequenced the mitogenome of Meghimatium bilineatum (Arionoidea: Philomycidae), a widespread land slug in East Asia. This is the first report on a mitogenome of the superfamily Arionoidea, and indeed on a terrestrial slug. The mitogenome of Meghimatium bilineatum comprises 13,972 bp and exhibits a novel, highly distinctive gene arrangement among the Stylommatophora. Phylogenetic reconstructions based on the sequences of all protein-coding genes consistently recovered Meghimatium bilineatum as sister-group of the Succineidae. A phylogenetic reconstruction based on gene order, however, suggested a highly divergent tree topology, which is less credible when taking into account prior knowledge of stylommatophoran relationships. Our CREx (Common interval Rearrangement Explorer) analysis suggested that three successive events of tandem duplication random loss (TDRL) best explain the evolutionary process of gene order rearrangement in Meghimatium bilineatum from an ancestral stylommatophoran mitogenome. The present example offers new insights into the mechanisms of mitogenome rearrangements in gastropods at large and into the usefulness of mitogenomic gene order as a phylogenetic marker.

Aegista aubryana is an endemic land snail in China. The complete mitochondrial genome of A. aubryana was first determined using long PCR reactions and primer walking method (accession number KT192071). The genome has a length of 14 238 bp, containing 37 typical mitochondrial genes (13 protein-coding genes, 22 tRNA genes and 2 rRNA genes). The base composition of the whole heavy strand is A 31.32%, T 37.86%, C 14.46% and G 16.36%. The results of phylogenetic analyses showed that the A. aubryana is most closely related to Mastigeulota kiangsinensis. This new complete mitochondrial genome can be the basic data for further studies on mitogenome comparison, molecular taxonomy and phylogenetic analyses in bradybaenid snails and Molluscs at large.

Mastigeulota kiangsinensis is an endemic and widespread land snail in China. The complete mitochondrial genome of M. kiangsinensis was first determined using long PCR reactions and primer walking method (accession number KM083123). The genome has a length of 14,029 bp, containing 37 typical mitochondrial genes (13 protein-coding genes, 22 tRNA genes and 2 rRNA genes). The base composition of the whole heavy strand is A 29.48%, T 37.92%, C 14.38% and G 18.22%. Gene order of M. kiangsinensis is identical to Euhadra herklotsi, but gene rearrangements are found compared with other mitochondrial genomes described in Stylommatophora. tRNAThr is located in COIII, which has not been found in other helicoids so far. This new complete mitochondrial genome can be the basic data for further studies on mitogenome comparison, molecular taxonomy and phylogenetic analysis in land snails and Molluscs at large.