Cockroaches Lab Report

Madagascar hissing cockroaches (Gromphadorhina portentosa), ectotherms that were easily observable and subjectable to habituation, were used to compare differences in standard metabolic rates between organisms. The hypothesis is that the habituated G. portentosa will have a lower weight specific metabolic rate than the non-habituated G. portentosa. To measure metabolic rates of habituated and non-habituated cockroaches that were either male or female, the cockroaches were put into a flow meter apparatus that calculated the amounts of CO2 they gave off during respiration. The mean weight specific metabolic rate for the habituated males was 2.00 x 10-3 +- 1.08 x 10-3 (ml x CO2)/(g x min) and for the non-habituated males the mean was 2.40

The metabolic rate can vary depending on conditions so before any metabolic rate is measured the organism must be fasting and also at a resting state. It is important to understand the differences between the G. portentosa organisms so that we can better understand how metabolic rates work. Since the cockroaches were to be handled by humans prior to having their metabolic rates measured, two groups of cockroaches were used in the experiment. One of these groups was habituated and essentially more comfortable with humans and the other group was non-habituated. The hypothesis is that the habituated G. portentosa will have a lower weight specific metabolic rate than the non-habituated G. portentosa. In an experiment testing the habituation of G. portentosa, Davis and Heslop found that habituation does have an effect on behavior of G. portentosa by reducing the amount of discrete hisses they exert (Davis and Heslop 2004). This leads us to wonder if habituation has an effect on standard metabolic rates between G. portentosa organisms. Stressful stimuli are thought to be costly when it comes to energy expenditure.

The mean weight specific metabolic rate for the habituated females was 2.03 x 10-3 +- 1.08 x 10-3 (ml x CO2)/(g x min) and for the non-habituated females the mean was 2.15 x 10-3 +- 1.12 x 10-3(ml x CO2)/(g x min) and the weight specific metabolic rate for the habituated females was not significantly different from the weight specific metabolic rate for non-habituated females