Figure 1.

General overview of Trichoplax behavior. (A) Trichoplax adhaerens (photo) is a simple, irregularly shaped flat animal with three cell layers. Muscles, neurons, gastric cavities, or any organs are absent. Scale bar = 0.1 mm. (B) Example of Trichoplax movement and tracking. Superimposed images of an animal every 60 s are shown. Black dots mark the positions of animal centroid every 10 s. (C) The sequence of ten images shows the feeding cycle of Trichoplax on the cyanobacterial biofilm. Images were captured every minute. The animal ceases movement and expands at the beginning of each feeding cycle. The body edge is attached to a substrate, enzymes are secreted, and digested food is absorbed. Digestion is enhanced by churning movements of the central part of the animal. After a digested food is absorbed, the animal detaches its edges, contracts, and resumes movement. Each cycle takes approx. 10–20 min. (D) The plot of the body area and crawling speed (mm/min) for representative animal feeding cycles on cyanobacterial biofilm. Body area increases at the beginning of each feeding cycle and decreases at the end of each cycle. Locomotion is suppressed during each feeding cycle.