Physiological Effects of a Hypotonic Environment

Abstract

ABSTRACT Numerous studies have been published on the extent to which aquatic animals can maintain internal environments differing in osmotic pressure from their surroundings. In the case of polychaete worms, it has been shown that some species, especially Nereis diversicolor, can maintain a considerable degree of hypertonicity, even in very dilute brackish water, while in others, such as Arenicola marina, the internal and external fluids are always isotonic (Schlieper, 1929; Beadle, 1937; Zenkewitch, 1938). These facts have been correlated with the extent to which the various species can invade brackish water. In one respect, however, our knowledge is at present very deficient. Remarkably little—in the case of polychaete worms, nothing—is known about the extent to which the tissues of animals can tolerate dilution of their bathing media. Information on this question is evidently necessary if the significance of the body-fluid data is to be properly understood.