. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MELIBE SWIMMING BEHAVIOR 149 often swam multiple times in response to a single sea star contact. If these multiple swims are viewed as one long swim episode, then in general, "stronger" stimuli (sea star>salt>pinch) caused animals to respond more quickly and swim longer compared to "weaker" stimuli. All the crabs and anemones tested, as well as the sea stars other than Pvcnopodia. elicited no responses at all in Me- libe. Neither animal seemed to take any notice of the other's presence. When contact
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MELIBE SWIMMING BEHAVIOR 149 often swam multiple times in response to a single sea star contact. If these multiple swims are viewed as one long swim episode, then in general, "stronger" stimuli (sea star>salt>pinch) caused animals to respond more quickly and swim longer compared to "weaker" stimuli. All the crabs and anemones tested, as well as the sea stars other than Pvcnopodia. elicited no responses at all in Me- libe. Neither animal seemed to take any notice of the other's presence. When contact between crabs and nudibranchs occurred, the nudibranch would often simply crawl over the carapace of the crab without incident. No contact between the anemone and the nudibranch was ever observed. Some nudibranchs were left with crab and sea star predators for up to 48 h, with no signs of predation. Finally, in a number of cases, nudibranchs were placed on the oral surface of po- tential sea star predators, and no ingestion occurred. How- ever, we did not control for the state of hunger of the test predators, and on other occasions we have observed both P\cnopodin and anemones eating small specimens of Me- libe in the laboratory. In addition, Ajeska and Nybakken (1976) have reported that Pugettia, a crab found in Califor- nia kelp beds, is a predator of Melibe. Direction of swim Preliminary observations indicated that, when swimming, Melibe moved in a ventral direction, perpendicular to the long axis of the foot. To test this hypothesis, we analyzed the instantaneous swimming direction of seven animals, in 5-s intervals, as described in the Materials and Methods. Five of these animals moved, on average, in a direction that varied less than one standard deviation (14°) from the predicted direction (90° from the long axis of the foot). The variance angles of the other two animals were only slightly different than predicted (Fig. 4). These data support the hypothesis that the g
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
