Micromorphology and ultrastructure of Caribbean sclerosponges. 1. Ceratoporella nicholsoni and Stromatospongia norae (Ceratoporellidae: Porifera)

Fine structural analysis of living tissue of the sclerosponges Ceratoporella nicholsoni and Stromatospongia norae , collected near Discovery Bay, Jamaica, between 1984 and 1986, was carried out using transmission and scanning electron microscopy (TEM and SEM). The thick dermal membrane of these sponges is covered by exopinacocytes having a "T" shape in sections perpendicular to the surface. A dense, complex glycocalyx is produced at the surface of these cells. Choanocyte chambers are diplodal and unusually small. The inhalant and exhalant canals of both species are characterized by the presence of valvules, made by transverse lamellipodial processes of the endopinacocytes lining them. An abundant and diversified bacterial community occupies almost 20% of the mesohyl. A single layer of active basopinacocytes lines the mesohyl at the interface between the living tissue and the aragonitic skeleton.