Ultrastructural and cytochemical investigations on the renal appendages and their concrements in dibranchiate cephalopods (Mollusea, Cephalopoda)

Abstract

The renal appendages of the octopods Octopus vulgaris Lam., Eledone moschata Lam. and of the decapods of the order Sepioidea Sepia officinalis L., and of sea water suggest osmotic filtration combined with active ion transport and methods of light and electron microscopy and of cytochemistry. The cells of the excretory epithelium are polarised; in all species, they show a basal labyrinth with a thick positive PAS and alcian blue reaction. The cells contain numerous mitochondria, which show the crista type of internal structure, and in the basal as well as in the apical part there are lysosomal dense bodies with high phosphatase activity. The fine structure, the osmolality and the ionic composition of the blood, the urine and of sea water suggest osmotic filtration combined with active ion transport and apocrine excretory secretion and reabsorption. In Sepia only, crypts of the epithelium were found to contain spherical mixed crystals which contain Ca, K, Na, Mg, Cl, S, P according to the electron probe and cytochemical analysis; the matrix shows concentric layers, it gives a positive PAS and alcian blue reaction. The chemical composition, the genesis and the possible function of these crystals are discussed.