Megafaunal Community Structure of Andaman Seamounts Including the Back-Arc Basin – A Quantitative Exploration from the Indian Ocean

Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount – CSM) and a non-volcano (SM2) in the Andaman Back–arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from TeleVision guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only

First record of the genus Caprella and species Caprella danilevskii Czerniavski, 1868 (Amphipoda: Corophiida: Caprellidae) from Arabian Sea, North Indian Ocean

33-44The genus Caprella (Amphipoda: Caprellidae) has been recorded from all over the world oceans, whereas the species C. danilevskii Czerniavski, 1868 was only limited to southern parts of the Indian Ocean. Here, the occurrence of the genus Caprella and species C. danilevskii is described from the coastal waters of India for the first time, thus extending the distribution of this species to the northern Indian Ocean. The specimens of C. danilevskii were collected from macroalgae located at the rocky intertidal coast at Veraval, Gujarat, India. A detailed description of the specimen from the Indian region was provided, including explicit morphometric relations among the male and female sexes. Some abnormalities and special characters were observed in the population, which have not been discussed prior to this study. The species C. danilevskii could represent an introduction in the coastal waters of India; however it cannot be ignored that the species was present earlier or could have been overlooked