Salinity of the Medium and Its Effect on Respiration in the Sea‐Anemone

Abstract

The effects of pure salts and increase of salinity of the medium on marine cells and organisms, with respect to respiratory activity and metabolism, have been reported by a number of observers. (Warburg, i908; Meyerhof, i9iI; Page, 1929: Chambers and Reznikoff, i925: Gustafsen, 1921; Hess, 1930; Brooks, i919.) However, the sea-anemone, Metridium marginatum, has not been studied by the most accurate methods. These animals, exposed to currents of sea-water of varying salt-content, or when at the mouths of rivers quite often brought into contact with fresh and brackish waters, should exhibit some response to such a changing environment. Bodine (1928) has pointed out that KCl is toxic for the larvae, embryos and eggs of Fundulus, and that NaCl and CaCl2 are also quite toxic, with mixtures of K and Ca ions showing some antagonistic ion action causing them to be less toxic for the eggs, but quite toxic for the larvae and embryos. Pantin (I93i) and Pantin and Weil (I93i) have shown the reactions and adaptations for a flatworm to fresh, brackish and sea-waters. In most of the organisms studied, it is indicated that an increase in the NaCl content causes an increase in the metabolism as measured by oxygen uptake, while the addition of KC1 will also cause increased metabolism. The addition of CaCl2 to the medium usually causes a return to the normal respiratory rates, indicating an antagonistic ion effect. Increase in the salinity of the medium would be expected to bring a rise in metabolic rate, even though possibly only a temporary one, probably due to the toxic effect of increased salinity and osmotic pressure. A number of experiments were conducted with small specimens of Metridium in the respiratory chamber of the Thunberg-Winterstein microrespirometer (Thunberg, 1905: Fenn, I927), the animal being allowed to remain in the apparatus while experimental runs were made with the natural seawater as the immersion medium, with dilute or concentrated sea-waters of known salinity (Page, I928; McCallum, I926), or with the sea-water replaced by solutions of pure salts, A large number of experiments could be run on the same organism, the animal being allowed to settle down and fasten itself to the bottom of the respirometer chamber and live there, and at the conclusion of a series of experiments the unnatural medium was replaced by sea-water allowed to run continuously over the organism.