Influence of the Optic Tectum and Prosencephalic Structures on Visually Controlled Prey-Catching and Avoidance Behaviors in the Fire Salamander
In recent years J.-P. Ewert and his co-workers (see this volume) have made extensive quantitative neuroethological studies with regard to visual discrimination of prey and predator both in toads and frogs. Dealing with this subject I am comparatively investigating the influence of the optic tectum and various prosencephalic structures on visually controlled prey-catching and predator avoidance behavior in the fire salamander, Salamandra salamandra, which is an urodele and holds an inferior position on the phylogenetic scale. Quite similar to that described earlier in toads (Ewert, 1968) quantitative behavioral experiments in S.salamandra have shown (Himstedt et al., 1976) that prey capture is best activated by a stripe moving in the direction of its long axis (“worm configuration”) rather than by the same stripe whose longer axis is oriented perpendicular to the direction of movement (“antiworm configuration”). More specifically (Fig.lA), squares with an edge length of approximately 10mm are strongest releasers compared to stripes of corresponding length; but in the range between 20 and 40mm the releasing value of the square is between that of wormlike and antiwormlike stimuli. Predator avoidance behavior can be elicited by a big looming square or disc which simulates an airborne or terrestrial predator. Vibration or tactile stimuli are also effective in releasing escape behavior. Recent quantitative studies in juvenile and adult fire salamanders have shown that their preference for the worm configuration of a stripe against the antiworm configuration is invariant with regard to changes in the stimulus angular velocity (Fig.1B). This phenomenon, which is already known from the common toad, has been confirmed in S.salamandra also by W. Himstedt (unpubl. data).
KeywordsOptic Tectum Bufo Bufo Tecta1 Neuron Electrical Brain Stimulation Predator Avoidance Behavior
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