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

BUR[;(;RE"I, W. W., B. R. McMAHON, and J. W. COSTEIl.TON. 1974. Branchial waterand blood­ flow patterns and the structure of the gill of the crayfish Procambarus clarkii. Can. J. Zool, 52: 15111518. Water flow within the branchial chamber, blood flow within the gill filaments, and the line str.ucture of t~~ gill epithelium have been determined In the crayfish Procambarus clarkii. The epithelium ol the podobranch filaments. which IS 3.15-8.70 }L thick, represents the blood-to­ water diffusion distance. Blood flow within the filament is arranged in a bidirectional system that IS firs,t cocurrern and then countercurrent to the flowof water irrigating the gills. Morpho­ logical evidence suggests that gas exchan&e might occur JIl both directions, Shunting of blood occurs within the gill filament and its significance in countercurrent blood flow and gas exchange IS discussed.