Absorption des substances dissoutes dans le milieu, des particules et des produits de la digestion extracellulaire chez Actinia equina (Cnidaria, Actiniaria)

Abstract

The results of nutrition experiments with glucose 14C, leucine 3H, amino acids 14C, cyanophyceae 14C and lipids have permitted me to enlarge our present knowledge of actinian nutrition. Ectodermal absorption.--Glucose and amino acids dissolved in the sea-environment were rapidly absorbed by the ectoderm. The multiple tentacles of Actinia and their cell microvilli enlarged the ectodermal surface. There is no preoral digestion, and the macromolecules were not absorbed since the ectoderm does not possess phagocytic cells. Digestion and endodermal absorption.--Macromolecules, particles and prey were carried into the coelenteron. The prey were enclosed in the convoluted lower part of mesenteries where they were divided into fragments and molecules by enzymes secreted by the zymogen cells of the mesenterial filaments. The macromolecules, particles and prey fragments (up to a few micrometers) produced by this extracellular digestion, or collected in the environment, were absorbed by the phagocytic cells. The lipids were pinocyted by the same cells concentrated in some parts of the endoderm, but the smallest molecules (carbohydrates and amino acids) were immediately absorbed by the mesenterial filament cells in contact with the prey. The transfer (in both directions) of the different absorbed substances between the ectoderm and the endoderm was slow. Glucose seemed to diffuse through the mesoglea, while the amino acids and the macromolecules would be transferred by the mobile cells of the mesoglea.