Fig. 5. Right, the flow field measured at the crayfish plane of symmetry (vertical laser sheet LS2 in Fig. 2) averaged over 30 instantaneous measurements (30 s). The fluid converges towards the fan organs in the plane of measurements and escapes in the form of jets in a perpendicular direction (not shown). Reference segment at the bottom, 2 cm; reference vector, 1 cm s^–1. The negative image of the crayfish cut from a PIV image is shown for reference. The broken line indicates the contour of the blindfold which is shaded from the laser sheet and thus is not visible in the image. The animal's appendages are denoted on the left; LR1A, lateral right antennule; R2A, right second antenna; L2A, left second antenna; MR1A, medial right antennule; LL1A, lateral left antennule; ML1A, medial left antennule; FO1, FO2, FO3, extended exopodite of fan organs 1 to 3; RM, LM, endopodite of right and left third maxilliped. Note that lateral antennules LR1A and LL1A are lowered in front of the fan organs, exposing chemoreceptors to the inflow.