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EVIDENCE FOR IDIOTHETICALLY CONTROLLED TURNS AN D EXTRAOCULAR PHOTORECEPTION IN LYCOSID SPIDER S

1991; American Arachnological Society; Volume: 19; Issue: 3 Linguagem: Inglês

1937-2396

Jerome S. Rovner,

Animal Behavior and Reproduction

During some of the intervals between bouts of pheromone-stimulated courtship display, iso- lated maleRabidosa rabida (Araneae, Lycosidae) perform a single pivot. In an investigation of the control o f this turning behavior, males were tested under four conditions . Two of these were visual, a uniform environmen t or one with images, and two were non-visual, all eyes occluded or dim red lighting . The turning angle and the tendency to change the direction of turning were measured for the first three conditions, and no significan t differences were found . This suggests that the turns are controlled idiothetically . Another parameter, the tendenc y to perform the turns, was reduced under dim red light but not in blinded spiders under white light, the latte r suggesting the occurrence of extraocular photoreception . When animals organize their behavior wit h respect to spatial features, they use information obtained from external directing stimuli (alloth- etic orientation) or from internal sources (idioth - etic orientation). The latter may depend eithe r on proprioceptive information or on central ner- vous system (nonsensory) programs that contai n the necessary information for spatial executio n of movements (Schone 1984). The present study deals with the question of whether rotational lo- comotion that occurs during courtship behavior in isolated male lycosid spiders is influenced by visual stimuli or is under idiothetic control . The display of Rabidosa rabida (Walckenaer) occurs in discrete bouts. In each bout the palp s are waved in alternation, and then the right o r left leg I is extended coincident with palpal-pro- duced sounds . Both of the latter elements en d abruptly in synchrony. A pause follows, during which time a receptive female, if present, signal s her response. Thus, the male's distinct bouts o f display alternate with inter-bout intervals, pro- viding a basis for reciprocal signaling betwee n the sexes. When this species' display was quantitatively analyzed (Rovner 1968), the data were obtained from males in the presence of females . However, when males in isolation are stimulated to displa y by contact with the female's sex pheromone, an additional behavior occurs . During some of the inter-bout intervals, such males perform a singl e pivoting turn. Rovner (1991) hypothesized that this rotational locomotion represents a compo- nent of a local search pattern . Apparently, it is added to the behavior of a male in the courtship mode if he has failed to detect a responding fe- male during the early phase of courtship. Since turning behavior in animals can be in- fluenced by goal-related images or by the level of illumination (Schone 1984), I examine d whether such visual input plays a role in th e inter-bout turning behavior of isolated male R. rabida . I tested spiders in well-lit arenas with or without fixed images and also tested them unde r non-visual conditions: in darkness (dim red light ) or after occlusion of the eyes.