Blazing Beetles: The Effect Of Temperature On The Locomotion of A Namib Dune Beetle

Abstract

Deserts represent some of the harshest ecosystems for life to survive in. In order to thrive, species must find novel adaptations either through behavioral or physiological modulation. The Namib desert of Southern Africa is no exception. In the Namib, temperatures can swing from 10 to 30°C throughout the day. Previous studies have indicated that there is temperature dependence in muscle power output in ectotherms. With the Namib being an understudied ecosystem, the present study aimed to investigate if invertebrate muscle output is affected by wild temperature fluctuations. Onmyacris plana, a Tenebrionid beetle endemic to the dunes of the Namib, was chosen due to being dorsally flattened, which results in low heat storage capacity. Although the thermoregulatory strategies, running ability, size and metabolic needs of O. plana have been studied, there have been no studies on the effect of temperature on the running performance of O. plana. We collected 8 beetles from the dunes and kept them in a vivarium in the lab. Beetles were subjected to three temperatures, to represent temperatures commonly experienced throughout the day. They were then placed on a 1-meter trackway in the lab and we made them run while recording them with a high-speed camera. Using the Matlab DLTdv5 digitizing tool we quantified their speed throughout the trials and analyzed differences in speed for the three treatments. We found no significant differences between running ability for beetles running at daytime temperatures and had significant difficulty in getting the beetles to run at temperatures experienced early in the morning. Our findings suggest that the beetles have a threshold muscle temperature which, if met, is sufficient for running at maximal speeds.