Fig. 2. Long-term recording over more than 7 days of the changes in projected area during contraction cycles of two specimens of T. wilhelma in the aquarium (A) and the open glass chamber (B). Light and dark periods are represented by white and grey backgrounds, respectively. Subcontractions, which differ significantly from regular contractions, are marked by asterisks. Experimental periods S1, S2 and S3 are represented by movies in the supplementary material. S1 represents a regular contraction series, S2 shows a series of subcontractions between regular contractions, S3 demonstrates the reaction of the sponge on a mechanical stimulation (amphipod attack). Note the adaptation phase in B after settling the sponge in the observation chamber.