Population Dynamics and Cyclomorphosis of Bosmina longirostris in Lake Yunoko.

Abstract

Population dynamics and cyclomorphosis of the cladoceran Bosmina longirostris were investigated in Lake Yunoko. The Bosmina population showed a marked decline in density in midsummer. Food limitation was considered to be the most probable cause of the decline. Food limitation for the Bosmina population might be promoted by competition with Daphnia longispina, which established a dense population in summer. B. longirostris showed a marked cyclomorphosis; they reduced the antennule length and mucro length in summer but recovered them in fall. The presence of predator Cyclops sp., seemed to be a major cause inducing the cyclomorphosis, since a significant positive correlation was obtained between the predator&s density and the lengths of the proturberant structures. © 1992, The Japanese Society of Limnology. All rights reserved.