Light and Transmission Electron Microscopy of the Granular Cell in the Skin Epidermis of a Cottid, Pseudoblennius cottoides

Abstract

The granular cell in a skin epidermis of a cottid fish, Pseudoblennius cottoides, is a volumi-nous one having coarse or finely granular contents which are acidophilic and may be regarded as containing basic and aromatic amino-acid groups from preliminary tests for protein histochemistry.This cell is mostly buried in the middle layers of the skin epidermis, and seems to attain the mature condition through graded developmental stages similar to those described by Thomson (1969) in a boxfish, Ostracion meleagris.Electron microscopy reveals that this cell at the developmental stage III is occupied by an enormous central vacuole containing relatively high dense granules without membrane-bounded structure.This vacuole is uniformly surrounded by several layers of larger vesicles having granules closely alike to those found in the central vacuole.The enormous central vacuole may probably be formed by successive ruptures of the vesicles.Considerably complicated interdigitations are visible between the granular cell and the filament-containing cell.The chara-cteristics of integumentary structures common to the teleosts endowed with the granular cells re-main to be solved.The function of this cell is also discussed.