Comparative Measurements of Water and Electrolyte Exchange in a Stenohaline and in a Euryhaline Polychaete

Abstract

The experiments described consist of measurements of the salt output and of the water intake of Nereis diversicolor and N. cultrifera in 20% sea water. These experiments establish two facts: (1) The ratio salt output/water intake is much greater for N. diversicolor than for N. cultrifera. (2) In N. diversicolor this ratio increases during imbibition to about double its initial value. In N. cultrifera there is little or no increase of this kind. From these facts it is concluded that N. diversicolor swells up less than N. cultrifera in a given dilution of sea water because the salt loss of N. diversicolor is more rapid than that of N. cultrifera, relative to the water intake. This provides at least a partial explanation of the ability of N. diversicolor to live in an estuarine habitat.