Branchial water- and blood-flow patterns and the structure of the gill of the crayfish Procambarus clarkii

Abstract

Water flow within the branchial chamber, blood flow within the gill filaments, and the fine structure of the gill epithelium have been determined in the crayfish Procambarus clarkii. The epithelium of the podobranch filaments, which is 3.15–8.70 μ thick, represents the blood-to-water diffusion distance. Blood flow within the filament is arranged in a bidirectional system that is first cocurrent and then countercurrent to the flow of water irrigating the gills. Morphological evidence suggests that gas exchange might occur in both directions. Shunting of blood occurs within the gill filament and its significance in countercurrent blood flow and gas exchange is discussed.