Oligochaete taxonomy – The rise of earthworm DNA barcode in India

Abstract

Oligochaeta is a class of segmented worms under the phylum Annelida that are characterised by the presence of tiny setae in each body segment. Earthworms are the main members, consisting of approximately 6200 species. Their ecological importance is well known as they are the major soil macro-fauna; Aristotle had named them as “the intestines of soil”. Classification of earthworms is a controversial issue since the introduction of modern taxonomical system on earthworm by Michaelsen in 1921. This is mainly because conventional identification using morphological and anatomical characters are complicated and confusing. The key diagnostic features such as the position and structure of the reproductive organs, clitellum and the associated tubercular pubertatis are not always reliable, particularly in different developmental stages, especially when the available specimens are the juveniles. DNA barcoding has offered a potential solution, even at the levels of identifying the juveniles or cocoons. Several genes including mitochondrial cytochrome-c oxidase I, 16S, 18S and 28S ribosomal RNAs, and protein-coding histone H3 genes have been introduced in the taxonomy and phylogeny of earthworm. It is anticipated that DNA barcoding will help conflicting taxonomy and further exploration of species diversity in India