Plasticity and conservatism in sclerites of a Caribbean octocoral

Abstract

Species level identification of octocorals is often based on the form of skeletal elements, the sclerites. Morphological variation in sclerites across and within habitats complicates both species delineation and the identification of specimens, both of which are essential for characterizing and understanding octocoral diversity. In order to quantify the effects of environmental plasticity on sclerite morphology, branches from the Caribbean gorgonian Antillogorgia bipinnata were removed from colonies at depths of 18 and 23 m and reciprocally transplanted between those sites and transplanted to an 8 m depth site for 7 months. Images of sclerites from those colonies were compared using elliptical Fourier analyses (EFA) of the sclerite outline. The length of scaphoids produced after transplantation was larger than those in older tissue, suggesting length was affected by the process of transplantation. Shape of scaphoids as detected in the EFA, differed between sites, and the reciprocal crosses suggest some of the difference was a plastic response to the environment. The results demonstrate the presence of some environmental plasticity in sclerite form. However, while detectable using EFA, the differences in form were not apparent in microscopical observations of the sclerites and thus would not affect identification of specimens nor traditional species delineation.