Complete mitochondrial genome of the radicine pond snail Radix plicatula (Gastropoda: Lymnaeidae).

Radix plicatula is broadly distributed in China, as well as Russia. It is one of the intermediate hosts of Fasciola species which leads to the spread of fascioliasis. Here, we first described the complete mitochondrial genome of R. plicatula. The mitogenome is 13,751 bp in length, containing 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. The contents of each base are 30.7% A, 39.6% T, 15.7% G, and 13.9% C. The sequence is AT rich (70.3%). Mitochondrial phylogenomic analysis showed that R. plicatula is close to R. auricularia.

Radix plicatula is a species of aquatic pulmonate gastropod mollusk in the family Lymnaeidae, broadly distributed in China, as well as in Russia (Liu et al. 1993). Radix species is one of the intermediate hosts of Fasciola species, which play a critical role in the spread of fascioliasis in humans (Correa et al. 2010; Lawton et al. 2015). Currently, approximately 20 million people have been infected with fascioliasis worldwide (Correa et al. 2010). Due to the high plasticity of the shell shape within the Radix species, it is difficult to classify them only according to morphological features (Pfenninger et al. 2006; Feldmeyer et al. 2010). Recently, some studies have performed the classification and phylogenetic analysis of Radix species and its allies (Bargues et al. 2001; Lawton et al. 2015; Aksenova et al. 2018). So far, however, in Radix only one species (i.e. R. auricularia from Germany) had the complete mitochondrial genome.

Here, we sequenced and annotated the complete mitochondrial genome of R. plicatula and reconstructed the phylogenetic relationships of 12 gastropod molluscs with the focus on Radix sensulato. Our results provide new insights into the relationship of radicine pond snails and genetic information for controlling the spread of Fascioliasis.

Specimens were collected from ponds in Nanchang (28°39′39″N, 115°47′20″E), China, in 2019. Morphological identification was following the literature (Yen 1939; Liu et al. 1993). The voucher specimens were deposited in the Nanchang University, Nanchang, China. Foot tissue of each specimen was preserved in −80 °C and then one individual (voucher number: ncuwxp-nc-201901) was used for genomic DNA extraction, followed by the Illumina Miseq sequencing platform with the strategy of 2 × 250 bp paired-ends. Complete mitochondrial genome was generated according to the previous study (Zhou et al. 2019).

Complete mtDNA sequence of R. plicatula is 13,751 bp in length (GenBank accession number: MN175602) and contains 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The light strand includes 11 genes (four PCGs, rrnS gene, and six tRNA genes) and the heavy strand includes 26 genes (nine PCGs, rrnL gene, 16 tRNA genes). The overall base composition of the mitochondrial genome is as follows: 30.7% A, 39.6% T, 15.7% G, and 13.9% C. The sequence is AT-rich (70.3%), similar to other Panpulmonata species (Feldmeyer et al. 2010; Liu et al. 2012; Zhou et al. 2019).

Compared with R. auricularia mitogenome, the gene order of R. plicatula is identical, but different from that of Ampullaceana balthica because of the positional mismatch for the tRNA-Trp gene. Phylogenetic analysis based on 12 PCGs and 2 rRNA genes showed that the family Lymnaeidae is monophyletic (BS = 100), and R. plicatula and R. auricularia had a close relationship (BS = 100) (Figure 1).

Figure 1.

Phylogenetic relationships of 12 gastropod molluscs using neighbour-Joining method. (GenBank accession numbers, Ampullaceana balthica: NC_026539; Radix plicatula: MN175602; Galba pervia: NC_018536; Radix auricularia: NC_026538; Pseudosuccinea columella: MH614274; Planorbarius corneus: NC_026708; Biomphalaria tenagophila: NC_010220; Planorbella duryi: KY514384; Biomphalaria sudanica: NC_038060; Biomphalaria glabrata: NC_005439; Physella acuta: NC_023253; Succinea putris: NC_016190).