The Effect of Radiation on the Longevity of the Cockroach, Periplaneta americana, as Affected by Dose, Age, Sex and Food Intake

The lethal effect of irradiation of the whole animal poses many questions as to the causes of death. Age is known to affect survival, and its effect on radiosensitivity has been variously assessed by a number of authors (1-8). Most of the data on which these studies have been made were obtained with mammals, and work with insects bearing on the relationship between age and sensitivity has been reported by Baxter and Tuttle (7). Anorexia is a prominent and immediate effect in most species, including the cockroach, as we have observed, and as it may persist it introduces the factor of starvation into the chain of events leading to death. One difficulty in assessing the influence of malnutrition induced by radiation is the short life span of most starved animals, whether irradiated or not. Hibernating animals would be suitable subjects were they available in abundance, but they would serve the purpose of special metabolic studies rather than the requirements for the study of normally active animals. Smith et al. (9) took advantage of the fact that an obese strain of mice and mice made fat by injections of goldthioglucose outlived those of normal size by many days when starved. Another way out of the difficulty is provided by the use of certain insects (10) which can endure starvation for long periods of time. The American cockroach, Periplaneta americana, has a life span of about 2 years as an adult and can endure starvation for many weeks (11). It can be easily reared and may be studied individually or collectively, and it is in several respects, such as size, longevity, and resistance to starvation, ideally suited to the study of the effects of radiation on the whole animal. The subject of this paper deals especially with the influence of age, starvation, and sex on survival. Since the penetration of the beam from a 2-Mev electron accelerator is approximately 1 cm in a substance of unit density and the resulting ionization increases