ENVIRONMENTAL CONTROL OF AMYLASE PHENOTYPE IN AMPHIPODS OF THE GENUS GAMMARUS

¹ Department of Biology, New York University, Washington Square, New York 10003

The amylases of three species of Gammarus amphipods, G. palustris, G. mucronatus, and G. lawrencianus, were studied using polyacrylamide gel electrophoresis. In all three species there are two principal zones of activity (Amy-1 and Amy-2), but occasional individuals exhibit a third band(Amy-X). Amy-X variants are more common in the deeper water species and in collections made during late winter or early spring than in the shallower water species or in summer collections. Experimental work shows that Amy-X can be induced by a diet rich in amylose or glycogen, but not by amylopectin or other foods, and by reducing the temperature at which they are maintained. It is hypothesized that the relative expressions of Amy-X and Amy-1 vary seasonally, and that this variation is an adaptive response to seasonal variation in diet, or conditions for the hydrolysis of substrate.