Comparative analysis on Sclerite Morphometry: a useful tool in the soft corals Lobophytum sp. (Sarcophytidae: Octocorallia: Anthozoa) identification from Andaman and Nicobar Islands, India
Keywords:Taxonomy, finger leather coral, lobes, octocoral, Andaman.
Soft corals are sessile, marine benthic organisms that play an important role in the coral reef ecosystem. The identification of soft coral species is challenging due to their morphological deviations. Octocorals are one of least studied groups in Indian waters due to a lack of expertise. A total of 60 species under the genus <i>Lobophytum</i> have been identified across the world’s oceans while India shares a total of 21 species including 18 species from the Andaman and Nicobar Islands. During the study, <i>Lobophytum</i> specimens were collected from coral reef regions of the Andaman and Nicobar Islands employing SCUBA-diving and hand-picking methods. Specimens were distinguished with lobate, plate-like, or capitate with a prominent stalk and dimorphic, fully retractile polyps into thick coenenchyme. Species were identified by extracting sclerites from various regions of the colony with 5% sodium-hypochlorite (capitulum surface and interior, base surface, and interior) examined under a stereo-zoom microscope. Sclerite structure and measurements, as well as type composition, have been examined in ten <i>Lobophytum</i> species in this study. In different regions of the same colony, the structural composition of each species sclerites varies. Sclerites of various shapes like club-shaped, rod-shaped, spindle-shaped, shuttles, capstans, dumbbells, cylindrical, barrel-shaped, irregular-shaped, and cross-shaped were observed in ten <i>Lobophytum</i> species. The colony morphology also plays a role in taxonomy and species arrangement in systematics. Aside from colony morphology, zooid arrangement in the colony is also important for species identification. The colour of the colonies does not have a proper role in species identification because they show a variety of colours due to their symbiosis with zooxanthellate microalgae. The colony colours are determined by zooxanthellate concentration, temperature, depth, and other environmental factors. However, after preservation, most colonies turn white, beige white, or cream in colour. Hence, Sclerite morphometric is a very useful characteristic for species identification in the <i>Lobophytum</i> species.