A Simple Device for Making Successive Photomicrographic Records of Large Groups of Developing Organisms

Abstract

In our analysis of the effect of ionizing radiation upon the cleavage of sea urchin zygotes we found it necessary to take successive photomicrographs of a large number of eggs, in different samples, which had been exposed to graded doses of ionizing radiation (Hsiao and Daniel, 1960). In order to estimate the rate of cleavage of the irradiated samples of fertilized eggs it is highly desirable to follow the cleavage of each egg in every sample and make photomicrographic records for later analysis. In other words, we need to take time-lapse pictures of the developing eggs subjected to different amounts of radiation so as to calculate the rate of cleavage and correlate it with dosage. After some preliminary trials we have put together, using commonly available materials, a simple device capable of taking photomicrographs repeatedly from the same field in a series of samples of irradiated eggs at specified time intervals. By lining up, according to time, prints made from each field, each egg can be identified and its cleavage followed from the first to the last frame in the series, and its rate of cleavage can be calculated. It occurs to us that investigators who have occasion to record developmental and other recurrent phenomena may find this simple device useful. A brief description of its method of construction and manipulation is reported in this paper.