We report the diversity, distribution and taxonomy of patellogastropod species from the entire mainland Indian coastline. A total of 77 coastal areas with rocky outcrops in the sandy shoreline, covering the entire mainland Indian coastline, were surveyed seasonally (four times a year) during December 2014 to December 2016. Coastal habitat characteristics and the diversity of all groups of limpets from the intertidal areas were recorded. Specimens were identified by external morphological shell and gill characteristics, by the colour of the foot, mantle fringe and radular characteristics. Ecological aspects like habitat preference were also used to distinguish species. Existing diagnostic characters were amended with newer characteristics emerged in our study. Seven species from two families, Nacellidae and Lottiidae, were found along the mainland Indian coastline. Each species is present with several polymorphic forms with different colour banding patterns. Our study revealed distinct variations in the radular teeth at the genus level, but less differences within genera. Patellogastropod diversity was greater along the west coast of India and only Cellana rota was available throughout the mainland Indian coastline.

Present communication reports the phylogenetic relationship between three groups of a marine limpet having different color banding patterns using COI sequencing. Samples were sequenced for mtDNA COI gene using universal primer. Comparative BLAST revealed that all three types were around 99.59% identical with Cellana karachiensis, first record of this species from Indian coasts. Apart from the morphological variations, the mtDNA COI gene analysis revealed around 1% nucleotide variations between these three types. The observed dissimilarity in COI sequences was possibly too little to consider these types as three different species. The derivation of amino acid positions indicated that these types could possibly be a complex of three cryptic species of C. karachiensis. The study proposes that the Oman and Indian populations of C. karachiensis might have derived by allopatric speciation due to geographical isolation. The group of these three cryptic species, sharing same habitat between themselves, possibly showed sympatric speciation.

A group of limpets, Cellana karachiensis, exhibiting phenotypic plasticity were examined from Gujarat coastline India, using molecular phylogeny. Previous examination of the COI genes established the presence of three different haplotypes X, Y and Z, while present study showed three more haplotypes X, X and Z. Thus, a total of six COI gene haplotypes, having 99.23% to 99.85% sequence similarity, were observed with variations at six sites. Bayesian phylogenetic analysis shows divergence of lineages X-Y, X-X and Z-Z. Careful observation of nucleotide alterations showed a nonrandom mutation with more A↔G and C↔T transitions between closely related species of the genus Cellana. A stretch of 17 base pair, within COI region, was marked as region with high degree of variability between species of Cellana. Results suggest that this could be the beginning of speciation, with partial or complete reproductive barrier or these are already distinct species in different stages of evolution.

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Present study reports the habitat preference and spatiotemporal variations in the population abundance of limpetsCellana karachiensisandSiphonaria siphonariainhabiting rocky intertidal zones of Veraval coast, Kathiawar Peninsula, India. The entire intertidal zone of the Veraval coast was divided into five microsampling sites based on their substratum type and assemblage structure. Extensive field surveys were conducted every month in these microsampling sites and the population abundance of two limpet species was analyzed using belt transect method. The results revealed thatC. karachiensiswas the dominating species at microsampling Site-1 (having rocky substratum) possibly due to its ability to tolerate high desiccation, salinity, and temperature fluctuations, while theS. siphonariawas found to be the most dominating species at microsampling Site-2 (having rocky substratum with abundant algal population) possibly due to their preference for the perpetual wet areas. The study also indicated thatS. siphonariapreferred upper littoral zone where the green algae were abundant whileC. karachiensispreferred the spray zone, where it faces almost no competition for space and food with other molluscs. The condition of the spray zone is very harsh for other species to survive.