Effects of ultraviolet radiation on the early larval development of Rana pipiens

Abstract

Effects of ultraviolet radiation of known spectral distribution on hatchability of ova and early larval growth are reported. The source of radiation was an air-cooled quartz mercury lamp (Victor X-ray Corporation) operated at 70 volts at a distance of 25 cm. from the ova or larvae. During exposures all eggs or larvae were kept in about 1.5-2 cm. of water, which is found by actual spectrograms to absorb wave lengths shorter than 240 m[mu] and to minimize in intensity those from 407 to 240 m[mu]. Fifty ova, collected on the morning following deposition, were placed in each of 6 glass containers. Three of the groups were placed in daylight under window glass and 3 in a dark cabinet at a temperature slightly lower than the temperature of those kept in the light. Certain groups were exposed for 1 minute daily, others for 2 minutes daily, while control groups were maintained in each of the environments. Variations from the normal pattern of development were not evident externally during the 1st 24 hours; but were recognized following the 2nd exposure. Regions of highest metabolic activity, such as the nervous system and sense organs, were most responsive to radiation. Only gross observations on the exposed larvae are recorded, and only those in the 1st week of growth.