Cyclomorphosis in Daphnia galeata mendotae Birge and D. retrocurva Forbes as a predator-induced response

SUMMARY. 1. Populations of Daphnia galeata mendotae and D. retrocurva were exposed for one generation to predators enclosed in mesh bags. The exposed Daphnia showed adaptive morphological changes that mimic cyclomorphosis in nature. The invertebrate predators Chaoborus and Notonecta induced longer helmets, while the fish Lepomis induced shorter bodies but had no effect on helmet length. Longer tail spines (relative to body length) were induced by Notonecta and Lepomis.
2. The responses of D. retrocurva were influenced by algae concentration, with the more extreme responses occurring at a higher food concentration and higher lipid index.