CHLORIDE EXCHANGES IN RAINBOW TROUT (SALMO GAIRDNERI) ADAPTED TO DIFFERENT SALINITIES

Abstract

Estimated of rates of exchange of body Cl, both total exchanges and exchanges across the integument and by way of the gut and kidneys, have been made in rainbow trout acclimatized to various salinities between fresh water and sea water (salinity 32%). Radioactive Cl-36 was used as a tracer. Neither total Cl exchanges nor integumentary exchanges varied in proportion with changes in the magnitude of the transintegumentary osmotic gradients maintained by the fish. This result is interpreted as indicating that changes in the permeability to water of the integument (probably primarily the gills) are an important part of the salinity adaptation process in rainbow trout. Laboratory diuresis and exchange diffusion of Cl are discussed as possible complications in this interpretation.