AbstractsPhysics

The behavioral repertoire of the sea anemone, Anthopleura xanthogrammica, was investigated to test for the occurrence of any immediate response to various regions of the electromagnetic spectrum. Monochromatic radiations in the visible and ultraviolet spectral regions were produced by a 150-watt xenon lamp or a ZOO watt mercury vapor lamp coupled to a Bausch and Lomb high intensity diffraction grating monochromator. X-rays were produced by a Maxitron 300 lc-Vp x-ray machine. Small-area (1.75 x 2.5 cm) exposures were given to: (1) the tentacles and oral disc, (2) the column, (3) the peristome, and (4) the pedal disc. The effective dose of each wavelength, sufficient to evoke a specific criterion of response, was determined for each reaction. The relative efficiency for effective wavelengths was calculated after correction for relative quantum efficiency. Action spectra, based on the relative efficiency data, showed different stimulative efficiency ranges and maxima in five distinct behavioral responses as follows: (1) tentacle flexion, from 340 nm to 600 nm with peaks at 360 nm and 500 nm, (2) tentacle retraction, from 248 nm to 400 nm with a peak at 280 nm, (3) oral disc flexion, from 350 nm to 600 nm with a peak at 360 nm, (4) column cavitation, from 345 nm to 450 nm with a peak at 350 nm, and (5) peristome depression, from 350 nm to 400 nm with a peak at 360 nm. Flexion of tentacles, without a decrease in length or diameter, resembled true photoreceptor responses by exhibiting a maximum stimulative efficiency in the same spectral region as many forms of invertebrates with identifiable photoreceptor systems. Tentacle retraction, characterized by a constriction of the apical and mesial portions of the tentacle, was considered to be a response to absorption of energy by membrane proteins of receptor cells or neurons, as evidenced by its peak of efficiency at 280 nm. Retraction was elicited by exposure to x-rays as well as to ultraviolet radiation. Oral disc flexion, column cavitation, and peristome depression appear to be caused by local contraction of muscles in response to radiation exposure. Column height reduction, that occurred concurrently with these responses, probably involved the longitudinal muscles of the mesenteries. The photoprocess initiating muscle contraction was not established. The disclosure of behavioral responses that can be differentiated according to the radiation spectral region, constitutes a novel finding with respect to the reactions of coelenterates to radiation exposure. The occurrence of these prompt reactions to x-ray, ultraviolet, and visible radiations indicates that a highly organized receptor system is not essential for radiation effects to be manifested in behavior.