Fig. 3. The duration of the inflation–contraction cycle depends on the resting diameter of the largest excurrent canals. Responses to agitation were measured in five sponges with the same sized (diameter) choanosome, but with varying sizes (1–5) of excurrent canals: 64.9, 76.9, 103.52, 154.13 and 213.35 µm, respectively. Sponges with larger excurrent canal diameters have a longer inflation and contraction period (500, 899, 1399, 2988, 2052 s, respectively), but the rate of propagation of contractions along incurrent and excurrent canals was not significantly different (in: 2.80±0.26 µm s^–1, N=5; ex: 3.30±0.45 µm s^–1, N=5, P=0.23). Bars denote ± s.e.m. of three measurements from one sponge (see supplementary material Fig. S2).