. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 s sm. f 16 FIGURE 5. Shell movements in Tridacna derasa. This animal was maintained in an outdoor tank and received direct sunlight. Shadows were monitored by a photocell clamped near the edge of the shell. Stimulus monitor (SM) traces indicate the onset of shadows and a light tactile brushing of the siphon (arrow) in the bottom record. Traces are numbered according to shadows presented at two-minute intervals. Valve adductions were recorded for seven consecutive stimuli but did not occur in response to six additiona
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 s sm. f 16 FIGURE 5. Shell movements in Tridacna derasa. This animal was maintained in an outdoor tank and received direct sunlight. Shadows were monitored by a photocell clamped near the edge of the shell. Stimulus monitor (SM) traces indicate the onset of shadows and a light tactile brushing of the siphon (arrow) in the bottom record. Traces are numbered according to shadows presented at two-minute intervals. Valve adductions were recorded for seven consecutive stimuli but did not occur in response to six additional shadows at the same location (trials 9-11 were omitted). In trial 14, the position of the shadow was moved to cover a different set of eyes. Trials 15-16 were at the original site. and relaxation involves plateaus in the catch state as the valves reopen. It should also be noted that all of the valve movements recorded here can be attributed entirely to the adductor muscle, and not the pedal retractors. Through the byssus attachment and the fulcrum effect of the shell umbones, the pedal muscles exert considerable closing force when the clam is attached to its coral substrate (Stasek, 1965). However, in these experiments the byssus of T. maxima was attached only to loose gravel in the aquarium, while the larger T. derasa no longer possessed a byssus. Habituation of the visual response. The shadow response of Tridacna habituates to repetitive visual stimuli. For example, animals found in shallow water do not respond to the constant flickering of light caused by surface waves (Stasek, 1965). To characterize the behavioral decrement, shell movements of a large T. derasa were recorded in response to shadows given at two-minute intervals. An example of an habituation test sequence is presented in Figure 5. The magnitude of valve adduction decreases gradually over successive trials in response to a constant stimulus, that is, to shadows affecting. Please note that these images are ex
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
