Effects of Temperature and Sex on Metabolic Rate in Madagascar Hissing Cockroaches (Gromphadorhina portentosa)

Abstract

The differences in basal metabolic rate have been studied for numerous variables--like size, mass, sex, etc.--and continue to be a matter of significant importance (Garn et al. 1953). Many of the studies examining variance between sex have focused on endotherms, which are organisms that can maintain homeostasis through internal metabolic processes (McNab 1980); however, we want to focus on the differences in metabolic rate among different sexes in ectotherms. Gromphadorhina portentosa, also known as Madagascar Hissing Cockroaches, are native to a subtropical climate with optimal living temperatures between 22 and 24 degrees Celsius; higher temperatures (27 degrees Celsius or higher) see an increase in activity levels within the cockroaches (Mulder and Shufran 2017). We wanted to see how the male and female cockroaches differed in metabolic rate and how an increase in temperature--and thus an increase in activity--affected their metabolic rate. We hypothesized that the male cockroaches would have the highest metabolic rate for both the room temperature and warmer temperature. We tested this by using biochambers and vernier sensors to log their CO₂ output and calculate their metabolic rates. The results of our study concluded that males have a higher metabolic rate than females in both temperature groups; however, females had a higher percent increase between the two temperatures overall.