Authors: Emily J Lombardi, Candice L Bywater, and Craig R White
Published in: Journal of Experimental Biology
The oxygen and capacity-limited thermal tolerance (OCLTT) hypothesis proposes that the thermal tolerance of an animal is shaped by its capacity to deliver oxygen in relation to oxygen demand. Studies testing this hypothesis have largely focused on measuring short-term performance responses in animals under acute exposure to critical thermal maximums. The OCLTT hypothesis, however, emphasises the importance of sustained animal performance over acute tolerance.
The present study tested the effect of chronic hypoxia and hyperoxia during development on moderate to long-term performance indicators at temperatures spanning the optimal temperature for growth in the speckled cockroach, Nauphoeta cinerea.
In contrast to the predictions of the OCLTT hypothesis, development under hypoxia did not significantly reduce growth rate or running performance, and development under hyperoxia did not significantly increase growth rate or running performance. The effects of developmental temperature and oxygen on tracheal morphology and metabolic rate were also not consistent with OCLTT predictions, suggesting that oxygen delivery capacity is not the primary driver shaping thermal tolerance in this species.
Collectively, these findings suggest that the OCLTT hypothesis does not explain moderate to long-term thermal performance in N. cinerea, which raises further questions about the generality of the hypothesis.