Responses of Cyclops bicuspidatus thomasi to alterations in food and predators

Abstract

When Cyclops bicuspidatus thomasi was transplanted from Placid Lake (where C. b. thomasi was abundant) to enclosures in Gwendoline Lake where C. b. thomasi was rare, this species was able to grow, survive, and reproduce in Gwendoline Lake water with Gwendoline Lake crustacean plankton. Fertilization of a Gwendoline Lake enclosure increased the survivorship of C. b. thomasi about 22% over that observed in the unfertilized treatment. However, addition of the midge fly larvae common to Gwendoline Lake (C. trivittatus and C. americanus) to the enclosure plankton community resulted in a decrease in the standing crop of C. b. thomasi to a point at which samples with C. b. thomasi became difficult to obtain. When Chaoborus was in the enclosure, fertilization did not enhance the abundance of C. b. thomasi but rather improved the survivorship of Chaoborus first and second instar larvae, and this resulted in an acceleration of the C. b. thomasi nauplii decline.