Complete Mitochondrial Genome and Novel Gene Organization of Ryssota otaheitana (Pulmonata: Chronidae), and its Implications on the Stylommatophora Phylogeny
Amor M. Damatac II1* and Ian Kendrich C. Fontanilla1,2
1Institute of Biology, University of the Philippines,
Diliman, Quezon City 1101 Philippines
2Philippine Genome Center, University of the Philippines,
Diliman, Quezon City 1101 Philippines,
*Corresponding Author: amdamatac1@up.edu.ph
ABSTRACT
Whole mitochondrial genomes (mitogenomes) have been increasingly used as markers for phylogenetic inferences. In the Philippines, a marine snail from the Conidae family has been the only species to date whose mitogenome has been fully sequenced, despite the country’s rich malacofaunal diversity particularly in the terrestrial environment. In this study, we sequenced the complete mitogenome of the land snail Ryssota otaheitana (Chronidae), an endemic Philippine pulmonate species. The mitogenome is 13,888 bp in length and encodes the typical 37 genes – including 13 protein-coding, 22 tRNA, and 2 rRNA genes. Short intergenic spacers were found – including a reduced, 42-bp putative control region. Although the gene content is conserved, R. otaheitana showed a novel mitogenome organization involving the translocation of tRNASerine and NADH dehydrogenase subunit 4 gene segment. Combined with available stylommatophoran mitogenomes, different datasets from concatenated sequences of protein-coding and rRNA genes were used for phylogenetic reconstructions. Bayesian Inference (BI) and Maximum Likelihood (ML) trees congruently supported several monophyletic clades within the Stylommatophora such as the Helicoidea, Urocoptoidea, Orthurethra, and Limacoidea sensu lato (syn. ‘limacoid clade’). R. otaheitana is grouped with Deroceras reticulatum in the lower Stylommatophora and forms the monophyletic Limacoidea sensu lato. Both sequence-based phylogeny and gene order comparisons have led us to a hypothesis that Limacoidea sensu lato is at the base of the ‘non-achatinoid’ clade while supporting the division of ‘achatinoid and ‘non-achatinoid’ groups in the Stylommatophora. This study reports the first complete mitogenome from the Chronidae family, which can be used further for the molecular phylogeny of Philippine snails and gastropods at large. . . . . read more