Habitat-Specific variation in eyespot size of a benthic cladoceran

Summary Pigmented eyespot size of the benthic cladoceran Simocephalus exspinosus was measured in individuals sampled from four freshwater ponds that differed in the extent of visually-oriented predation. In ponds with such predation (from fish, salamander larvae, and dragonfly nymphs), eyespot size was found to be significantly smaller, relative to body size, than in a pond without visually-oriented predation. Reduction in pigmented eyespot size may represent an adaptation to reduce vulnerability to predation.