Figure 5: Cycles of nectophore contraction for a single four-member nectosome during forward asynchronous (0–1.6 s) and reverse synchronous (1.6–2.0 s) swimming.
From: Multi-jet propulsion organized by clonal development in a colonial siphonophore
(a) The per cent contraction was measured as the change in nectosac (the fluid-filled interior of a resting nectophore) cross-sectional area relative to the relaxed state. The different nectophores are designated by colour as in the icons above the contraction data. (b) Whole-colony speed. (c) Angular direction of the colony. Note that during the initial observation period (0–0.6 s) the colony swam with relatively consistent direction and speed. The two youngest, anterior-most nectophores contracted nearly simultaneously during that period and their balanced contractions maintained stable directionality. Alterations in this pattern, including the additional contraction of the larger, older nectophores altered the angular path of the colony. Contraction extent varied during the period and was most extensive during the synchronous, reverse swimming that is associated with escape swimming.
