The peristomial membrane of regular sea-urchins: Functional morphology of the epidermis and coelomic lining in paracentrotus lividus (lamarck)

Abstract

The functional organization of both the epidermis and the coelomic lining of the peristomial membrane in the regular sea- urchin Paracentrotus lividus is described and correlated with the extreme deformability of the peristomial membrane and with the «mutability» of its related dermis. The epidermis consists of a monolayer of columnar supporting cells mixed with ciliated sensory cells, the wide interspaces between these epithelial cells being occupied apically by a variety of cell types and basally by a conspicuous basiepithelial nerve plexus. The coelomic lining is a peripharyngeal coelomic epithelium consisting of apical monociliated peritoneocytes and subapical myocytes, and has an associated basiepithelial nerve plexus. Although the basic morphology of these epithelia is similar to that of corresponding tissues in other echinoderms, they both have significant structural adaptations and display the histological pattern of typical transitional epithelia, which enables them to match the wide range of deformations shown by the peristomial membrane in vivo. Histo- fluorescence techniques were employed to explore the innervation of the outer epidermis and the inner coelomic lining. © 1995 Taylor & Francis Group, LLC.