Stressed out underground?: Transcriptomics illuminates the genome-wide response to heat stress in surface and subterranean diving beetles

Published on by Perry Beasley-Hall
Subterranean habitats are environmentally stable with respect to temperature, humidity, and the absence of light. The transition to a subterranean lifestyle might therefore be expected to cause considerable shifts in an organism’s physiology; here, we investigate how subterranean colonisation affects thermal tolerance. Animals inhabiting extremely stable environments are known to lose the ability to mount a heat shock response, which involves the expression of heat shock proteins as a result of heat stress. Such organisms might be at particular risk of decline in the face of global temperature rises, but robust data on potential impacts on subterranean fauna are lacking. In this study we compare the heat stress response of two species of diving beetle in the genus Paroster: one surface-dwelling, the other restricted to a single aquifer. By sequencing transcriptomes of experimentally heat-shocked individuals, we demonstrate both species can mount a heat shock response at high temperatures, but the genes involved differ and more genes are differentially expressed in the surface species P. nigroadumbratus, which may imply a more robust response to heat stress. In contrast, the subterranean species P. macrosturtensis upregulated a major heat shock protein at milder temperatures, suggesting that while the species has retained a heat shock response, it may not be able to mount as robust a reaction to heat stress compared to its surface-dwelling relatives. Ultimately, the results presented here contribute to a wider, emerging narrative concerning weakened thermal tolerances in obligate subterranean organisms.

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