Fig. 5. Tritonia diomedea without rhinophores do not show navigational responses to prey and predator odour plumes. Each image is a mean projection of a motion enhanced video recording of a slug (s) crawling in the flow tank, showing slug movement (direction shown by arrowheads) and the dyed odour plume (`o', odour plume source; flow is from left to right). With rhinophores, slugs crawling cross-stream responded with upstream crawling when encountering a prey odour plume (A) or a downstream turn away from predator odour (B). Without rhinophores, slugs showed no response to odour plumes (C,D). Elapsed time (min) is shown in A–D. Scale bar, 25 cm. See Fig. 5 movies in supplementary material for the videos corresponding to A–D in this figure.