Meeting Abstract

P3.146  Friday, Jan. 6  Multimodal Integration in Praying Mantis Audition: Visual Information Modulates the Descending Ultrasound-evoked CNS Responses of Parasphendale agrionina DUQUE, Juan F.; FREUDENBERGER, Kelly; YAGER, David D.*; Univ. Maryland, College Park; Univ. Maryland, College Park; Univ. Maryland, College Park

Many male praying mantises fly at night, probably seeking pheromone-producing females. Most species have an ultrasound-sensitive ear in the metathorax that allows detection and successful evasion of the dominant nocturnal predator, echolocating bats. Auditory information carried by at least two auditory interneurons reaches the head by 12-13 ms. after the stimulus, and the evasive response begins ca. 50 ms. later. We asked whether visual input affects the descending neural response during the animal’s night. Under conditions of complete darkness or moderate light, we recorded the robust, multiunit descending responses in the lateral half of a prothoracic connective using a suction electrode. All measured parameters differed significantly after 15 min. in the dark versus after 15 min. in light. Responses in the light had, on average, a 15% shorter latency (26 vs. 31 ms.), a 59% shorter duration (274 vs. 457 ms.), and 33% fewer total spikes/stimulus (60 vs. 91). In addition, there was an average of 7.6 recognizable units in the light response vs. 9.4 in the dark. To eliminate the possibility that the differences were due solely to the novelty of a bright light during the night, we repeated the recordings in the animal’s daytime when bright light is normal. The patterns of response in the day were the same as at night, although for both light and dark conditions the latencies were shorter, spike numbers higher, and durations longer suggesting a circadian component. Thus, visual input strongly affects descending auditory responses. Because in the dark we saw greater numbers of spikes but longer latencies, the overall change is probably not a simple threshold shift.