Superimposed morphofunctional study of ion regulation and respiration in single gill filaments of the crayfish Astacus leptodactylus

Abstract

Using an in vitro perfusion method, a morphofunctional study was made of single filaments isolated from the podobranch of the fresh-water crayfish Astacus leptodactylus. Each filament was fixed for transmission electron microscopy directly after an electrophysiological study. This procedure allowed us to distinguish 2 filament populations on the basis of the electrical potential differences and the superimposed ultrastructural analysis. When both sides of the preparation were perfused with Van Harreveld saline, the potential difference was either zero for a first population of filaments or different from zero for a second one. The filaments of the first population were selectively sensitive to [Ca2+] changes but insensitive to [Na+] and [Cl-] changes in the external perfusion medium. Their epithelia were of the respiratory type, i.e., they were thin and poor in mitochondria. The filaments of the second population were sensitive to [Ca2+] and [Na+] changes. Their epithelia were of the ion-transporting type, i.e., they were thick, rich in mitochondria, and showed a developed basolateral membrane system.