Cockroaches on a treadmill: Aerobic running

Five species of cockroach were tested on a miniature treadmill at three velocities as O₂ consumption ( V ̇_O2) was measured: Gromphadorhina chopardi, Blaberus discoidalis, Eublaberus posticus, Byrsotria fumagata and Periplaneta americana. All cockroaches showed a classical aerobic response to running: V ̇_O2 increased rapidly from a resting rate to a steady-state ( V ̇_O2ss): t _{1 2} on-response varied from under 30 s to 3 min. Recovery after exercise was rapid as well; t _{1 2} off-response varied from under 30 s to 6 min. These times are faster or similar to mammalian values. V ̇_O2 varied directly with velocity as in running mammals, birds and reptiles. V ̇_O2 during steady-state running was only 4-12 times higher than at rest. Running is energetically much less costly per unit time than flying, but the cost of transport per unit distance is much more expensive for pedestrians. The minimal cost of transport (M_run), the lowest V ̇_O2 necessary to transport a given mass a specific distance, is high in cockroaches due to their small size. The new data suggest that insects may be less economical than comparable sized vertebrates.