THE PROMPT DETECTION OF IONIZING RADIATIONS BY CARPENTER ANTS

¹ The Radiation Center, Oregon State University, Corvallis, Oregon 97331

Carpenter ants exhibited behavioral responses to 10 R/sec (x-rays) within one second of the onset of exposure. Within the range of 0.05 R/sec to 80 R/sec the strength and duration of responses were proportional to the exposure rate. Latency was inversely related to exposure rate.

A comparison of behavioral reactions of normal subjects with subjects whose eyes or antennae had been removed or shielded, revealed that sensory receptors (probably olfactory) on the antennal flagella were primarily responsible for detection and led to the onset of prompt responses.

Bioelectric potentials were recorded from isolated eyes (electroretinograms) and isolated antennae (electroantennograms) during brief exposures to ionizing radiations. The results largely corroborated evidence derived from behavioral studies that eyes and antennal receptors are sensitive detectors of ionizing radiation. The strength of bioelectric responses varied directly with stimulus strength. Estimates of threshold exposures or doses, delivered in fractions of a second, indicated that the eyes and antennal receptors of the ant can detect x-ray and beta radiations in the millirad dose range.

X-ray and visible-light stimuli elicited electroretinograms with very similar characteristics, suggesting a common mechanism of action on the photoreceptor pigment in the ommatidia. The response to beta radiations displayed some unusual characteristics that cannot be explained at present.