Fig. 1. (A) Contraction patterns of two specimens (Tw1 and Tw2) of T. wilhelma, representing the changes in projected areas over an experimental period of 18 h. Tw1 was placed in the aquarium, Tw2 in a closed experimental reactor. Note the subcontraction (asterisk) of Tw2 at a time point when a regular contraction should have taken place if the rhythm of the former contraction series had continued; dotted lines, Tw1; broken lines, Tw2. (B) Comparison of average contraction cycle duration of Tw1 (83.3±11 min; N=12) and Tw2 (169.0±28 min; N=6).