Economic load-carrying in cockroaches

Energetic costs of carrying loads can significantly impact animal fitness but appear to vary dramatically among animals. For some they equal the cost of carrying an equivalent amount of extra body mass while others carry loads more economically. Locomotor systems can plastically respond to acute and chronic loading, but how such responses impact energetics of locomotion is unclear. We asked how loading affects the energetics of Blaberus discoidalis cockroaches at rest and during locomotion at various speeds, and if energetics change as animals adjust to chronic loading. Cockroaches carried loads economically as early as 24 hours after load addition, with no change in energetic costs during a 10-day period. We discuss the implications of these findings, and potential mechanisms underlying economic load-carrying in arthropods.