Seasonal population structures of two coexisting Diaptomus species.

Abstract

The Diaptomus siciloides and Diaptomus pallidus populations inhabiting a small Borrow Pit Lake on the Emporia State University campus were observed from March, 1979, through April, 1980. During the first two months of the study, the zooplankton community was recovering from a winter kill; and all copepods appearing in the samples were represented by naupliar stages only. Diaptomus siciloides was the first of the calanoid copepods to undergo development. One generation of Diaptomus siciloides developed during the study. Adult Diaptomus siciloides were first detected in the April, 1979, samples and reached a peak density of 14.3 individuals/liter in May, 1979. Development time for the generation was 55 days. Water temperature ranged from 17°C to 20°C during development. Adults of Diaptomus siciloides were either rare or absent in the samples during the rest of the study. Three generations of Diaptomus pallidus developed during the study. Development of Diaptomus pallidus generations occurred later than the development of Diaptomus siciloides. The shortest development time observed for a Diaptomus pallidus generation was 46 days and occurred from mid-July to early September with water temperatures between 24°C and 30°C. Development of Diaptomus pallidus was slower at cooler water temperatures and appeared to cease during the winter. The results of this study indicated that the optimal developmental time for Diaptomus siciloides occurred during periods of the cool water temperatures experienced during early spring and late fall. Optimal developmental time for Diaptomus pallidus occurred during the warm water temperatures of the summer months.