REGULATORY ELEMENTS IN THE SKIN EPITHELIUM OF SACCOGLOSSUS MERESCHKOWSKII (ENTEROPNEUSTA, HEMICHORDATA): ELECTRON MICROSCOPIC AND IMMUNOCYTOCHEMICAL STUDY

Abstract

The aim of this investigation was to demonstrate the regulatory elements in the skin epithelium of Enteropneusta which are supposed to be related to the chordate ancestors. Using electron microscopy, it was found that in the skin epithelium of a representative of enteropneusts Saccoglossus mereschkowskii, the basal parts of some epitheliocytes took part in formation of a nerve layer. These cells were considered as receptor ciliated cells. The granular epithelial cells were shown to release secretion according to both exocrine and endocrine mechanism; these cells were characterized as endocrine-like regulatory cells. Fine granular cells possibly represent special receptor-endocrine-like cell type. The immunocytochemical detection of FMRFamid neuropeptide localization in histological sections confirmed the electron microscopic data on the presence of receptor and endocrine-like cells in the epithelium. It is suggested that the skin epithelium of Enteropneusta contains a peculiar neuro-endocrine regulatory system that is represented by receptor cells, receptorendocrine-like cells of an open type and nerve elements of the nerve layer.

Keywords

skin epithelium / ultrastructure / immunocytochemistry / Enteropneusta / evolution

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