K. G. Sivaramakrishnan

Influence of certain forces on evolution of synonymous codon usage bias in certain species of three basal orders of aquatic insects

Forces that influence the evolution of synonymous codon usage bias are analyzed in six species of three basal orders of aquatic insects. The rationale behind choosing six species of aquatic insects (three from Ephemeroptera, one from Plecoptera, and two from Odonata) for the present analysis is based on phylogenetic position at the basal clades of the Order Insecta facilitating the understanding of the evolution of codon bias and of factors shaping codon usage patterns in primitive clades of insect lineages and their subtle differences in some of their ecological and environmental requirements in terms of habitat–microhabitat requirements, altitudinal preferences, temperature tolerance ranges, and consequent responses to climate change impacts. The present analysis focuses on open reading frames of the 13 protein-coding genes in the mitochondrial genome of six carefully chosen insect species to get a comprehensive picture of the evolutionary intricacies of codon bias. In all the six species, A and T contents are observed to be significantly higher than G and C, and are used roughly equally. Since transcription hypothesis on codon usage demands A richness and T poorness, it is quite likely that mutation pressure may be the key factor associated with synonymous codon usage (SCU) variations in these species because the mutation hypothesis predicts AT richness and GC poorness in the mitochondrial DNA. Thus, AT-biased mutation pressure seems to be an important factor in framing the SCU variation in all the selected species of aquatic insects, which in turn explains the predominance of A and T ending codons in these species. This study does not find any association between microhabitats and codon usage variations in the mitochondria of selected aquatic insects. However, this study has identified major forces, such as compositional constraints and mutation pressure, which shape patterns of codon usage in mitochondrial genes in the primitive clades of insect lineages.

Abundance, Altitudinal Distribution and Swarming of Ephemeroptera in Palni Hills, South India

The nymphs of 17 genera of Ephemeroptera representing seven families were collected during a survey of mayflies at different altitudes in Palni hills. Densities ranged between 5–80 nymphs m-2 at the sites investigated. Species richness of most mayfly assemblages was high whilst the abundance of individual species was low. Leptophlebiidae and Heptageniidae dominated larger streams at different altitudes whereas Baetidae and Caenidae exhibited overlapping distribution patterns. Historical immigration, assured perennial flow of a stream and its pollution-free nature appear to be the factors mainly influencing the distribution of a few biogeographically significant genera of Leptophlebiidae. Noon swarming of leptophlebiid and baetid mayflies was observed at a few sites at higher altitudes.

Biosystematic studies of south Indian Leptophlebiidae and Heptageniidae in relation to egg ultrastructure and phylogenetic interpretations

Previous work on the importance of egg ultrastructure to the taxonomic and phylogenetic studies of Ephemeroptera with special emphasis on the two schistonotan families, Leptophlebiidae and Heptageniidae is reviewed. The chorionic sculpturings, the types of micropyles and attachment structures of the eggs of south Indian mayfly species belonging to 8 genera of Leptophlebiidae and 3 genera of Heptageniidae have been studied through scanning electron microscope.The present study confirms the earlier observations that the Leptophlebiidae are most certainly of enough distant relationship with the Heptageniidae to warrent inclusion in separate superfamilies viz Leptophlebioidea and Baetoidea. Whereas the structural modifications on the eggs are significant in contributing to the taxonomy of both the families at the generic level, submicroscopic examinations of chorionic structures provide data for the separation of different species and species complexes in Leptophlebiidae.

A new species and a new record of the subgenus Dilatognathus Kluge 2012 (Ephemeroptera: Leptophlebiidae: genus Choroterpes Eaton, 1881) from India

A new species belonging to the subgenus Dilatognathus of the genus Choroterpes is described based on larvae collected from Andaman and Nicobar Islands. Choroterpes (Dilatognathus) nicobarensis n. sp. can be distinguished from all other species of Dilatognathus by the absence of a tusk on the maxillary apex, has ventro-apical flange and dentiseta directed distally, as in Choroterpes other than Dilatognathus. Choroterpes (Dilatognathus) nigella (Kang & Yang 1994) is newly recorded based on larvae collected in Arunachal Pradesh, Meghalaya and West Bengal. Remarks on the evolution of the mouth apparatus of the subgenus Dilatognathus are given.

A new species of mayfly (Ephemeroptera: Leptophlebiidae) from the Western Ghats, India

A new species of mayfly Choroterpes (Euthraulus) nambiyarensis sp. nov. is described from the nymphs collected in the southern Western Ghats, India. The types are deposited in the Zoological Survey of India, Kolkata, India.

Two new mayfly species (Baetidae) from India

Two new mayfly species belonging to the family Baetidae, namely Platybaetis arunachalae sp. nov. and Indobaetis michaelohubbardi sp. nov., are described from nymphs collected in the Ramanadi and Tamiraparani rivers, respectively, of the southern Western Ghats, Tamil Nadu, India. Generic diagnosis based on nymphs and key to known species of Platybaetis and Indobaetis are also provided.

Annotated checklist of ephemeroptera of the Indian subregion

Abstract The paper provides an uptodate checklist of species of Ephemeroptera of Indian subregion of Oriental region (India, Pakistan, Nepal, Bhutan, Myanmar and Sri Lanka) with synonyms and distribution. A total of 60 genera and 204 species have been listed.

Behavioural strategies of emergence, swarming, mating and oviposition in mayflies

Behavioural strategies of emergence, swarming, mating and oviposition in mayflies are reviewed in the light of available literature.

A new species of symbiocloeon (Ephemeroptera: Baetidae) associated with a freshwater mussel from India

Abstract A new species of Symbiocloeon, residing in the gill lamella of an ancient gondwanian species of freshwater mussel, Pseudomulleria dalyi (Unionoida: Etheriidae) is described from nymphs collected from the Tunga river of Western Ghats, Shimoga district, Karnataka, India. The diagnostic nymphal characters of Symbiocloeon madhyasthai, sp. nov., are given and differentiated from Symbiocloeon heardi Muller-Liebenau.

Description of the Female imago and eggs of Indialis badia Peters & Edmunds (Ephemeroptera: Leptophlebiidae)

Abstract The previously unknown female imago and egg of Indialis badia are described. An additional locality is given for the species in South India.