Molecular tools for identification and classification of Myxozoan parasites (Cnidaria: Myxosporea) in India: Current status

Abstract

A substantial literature on myxosporea has been published to date using morphological characters and specificity of host tissue. Currently, there are some 2400 nominal species of myxosporea classified to 17 families and 64 genera. Approximately 300 species have been described from India and most of them have been described solely on the basis of morphological characteristics. Molecular markers like small subunit ribosomal (SSU) and large subunit ribosomal (LSU) DNA have been used worldwide for the identification and validation of fish myxosporeans. Maximum likelihood phylogenetic tree based on SSU rDNA sequences was used to study the phylogenetic relationship among myxosporeans infecting Indian fishes. Myxospore phylogenies disagree with traditional spore-based classification systems, probably due to extreme plasticity in myxospores morphologies that have resulted in extensive convergence. Morphological similarities exist among myxosporea that encounter several problems in categorizing them. That’s why present-day research has shifted to molecular techniques for identification and correct systematics of myxosporeans. Molecular studies of myxozoans in India are still scarce and in infancy. To address persisting taxonomic and phylogenetic discrepancies, validation of these species by molecular tools is needed, because earlier species were reported only on the basis of morphological data. Therefore, the present study has summarized existing molecular data and current status of molecular taxonomy of myxosporeans parasitizing fresh and marine water fishes of India along with the approaches of myxozoan phylogenetics and information about the molecular markers, their interpretation in the identification of myxozoans parasitizing fishes.

The occurrence of known Myxobolus and Thelohanellus species (Myxozoa, Myxosporea) from Indian major carps with the description of Myxobolus bandyopadhyayi n. sp. in West Bengal

“…However, the description of only a part of these species has been complemented with molecular data, therefore it might be possible that several synonymous species exist among them. Gupta et al (2021) mention 40 species of myxobolids with sequence data based on only a limited number of research studies ( Singh and Kaur, 2012 ; Kaur, 2014 ; Rajesh et al, 2014 ; Abraham et al, 2015 ; Székely et al, 2015 ; Chaudhary et al, 2018 , 2019 ; Gupta et al, 2018 ). Myxozoan samples were obtained from the genera Labeo , Gibelion and Cirrhinus collected from West Bengal fish farms and local fish markets which showed signs of myxosporean infections.…”