Figure 1.

Expanding specimen of Tethya wilhelma Overlay of a time-lapse series of outlines of the projected body area of T. wilhelma, representing an expansion from fully contracted state at t = 0 min to fully expanded state at t = 45 min. In addition, the 8-bit image of the contracted sponge body at t = 0 min is displayed on top of the overlay, to give an impression of the sponge and it's body extensions. Like the body outlines, the measurement of the projected area is computed automatically using the software ImageJ 57 and own macro functions. Outline and overlay were computed using ImageJ, too.