Size variation and geographical distribution of the luminous earthworm Pontodrilus litoralis (Grube, 1855) (Clitellata, Megascolecidae) in Southeast Asia and Japan

Abstract

The luminous earthworm Pontodrilus litoralis (Grube, 1855) occurs in a very wide range of subtropical and tropical coastal areas. Morphometrics on size variation (number of segments, body length and diameter) and genetic analysis using the mitochondrial cytochrome c oxidase subunit 1 (COI) gene sequence were conducted on 14 populations of P. litoralis from Southeast Asia and Japan. Statistical inference on morphometric data revealed significantly different size variations in the body length and diameter among these 14 populations of P. litoralis. However, discordance between the morphometric and mitochondrial COI gene-based phylogenetic analyses was evident, where the size variations in P. litoralis showed a different pattern from the COI genetic differences. The update on the current distribution of P. litoralis is reported and revealed different aspects of the littoral habitat characteristics between Southeast Asia and Japan.