RELATIONSHIP BETWEEN MORPHOLOGY AND HYDRODYNAMICS DURING SWIMMING BY THE HYDROMEDUSAE AEQUOREA-VICTORIA AND AGLANTHA-DIGITALE

Hydrodynamic forces acting upon adult swimming Aglantha digitale and A equorea victoria ia were estimated by combining empirical kinematic da ta with the model of Daniel (1983). Forces varied in magnitude during bell pulsation and recovery. The acceleration reaction and inertial re sistance were the dominant instantaneous terms. However, the net force s (each hydrodynamic force totaled over complete pulsation cycles) wer e different for the two species. Ag. digitale maximized acceleration r ates and minimized the acceleration reaction: drag was the dominant ne t force. Ae. victoria ia minimized acceleration rates and maximized th e acceleration reaction: the acceleration reaction was its dominant ne t force. A new finding of this work was that oblate medusae such as Ae . victoria may be efficient for continuous swimming due to a positive net contribution of the acceleration reaction to forward motion once t he medusa has begun swimming.