Indian Journal of Science and Technology

Abstract

Many ecological studies on the diversity and distribution of freshwater planktonic cyclopoid copepods are being published and they depend upon the molecular methods for accurate taxonomic identification. The greater coverage of reference species in the genetic database, GenBank, with the decreasing costs for DNA sequencing, have made large scale plankton identification studies using molecular methods, more feasible. Here, we present a practical molecular approach to identify Thermocyclops decipiens, collected from Karapakkam Temple tank, Chennai, India. Molecular identification methods of cyclopoids included amplification of 18S rDNA. The present work on molecular phylogenetic analysis of freshwater cyclopoid copepods deals with the evolutionary relation among 12 species of freshwater cyclopoid copepods. The 18S rDNA sequences were analyzed using ClustalW, Maximum Likelihood method, Distance method and UPGMA method. The Multiple Sequences Alignment showed less score value of 52 between Thermocylops decipiens and Mesocyclops thermocyclopoides. Among 12 species of freshwater cyclopoid copepods, Mesocyclops edax and Mesocyclops darwini were single phyletic group in UPGMA method. By Maximum Likelihood analysis of Mesocyclopos thermocyclopoides, confident limit was 1.9870–7.30265 with positively significant at p<0.05 level and the distance compared with other species was 4.643516–5.873569.
Keywords: Maximum Likelihood, Nuclear 18S rDNA, Phylogeny, Thermocyclops, UPGMA.