Sex differences in auditory function of the desert locust.

Age-related auditory decline manifests across the animal kingdom, from humans and mice to zebrafish and insects. Sex differences in auditory decline are established for humans, but there is now evidence in mice and even zebrafish. Here, we found sex differences in auditory decline in an insect, the Desert Locust and investigated its biological basis. We profiled gene expression in a dedicated auditory organ, Müller's organ to understand the genetic underpinning of sex differences and measured sound-evoked transduction currents and electrophysiological properties of auditory neurons to quantify auditory decline. We analysed gene expression in Müller's organ of young locusts where sex differences in auditory function were absent and in older, noise-exposed locusts where sex differences in auditory function were maximal. The auditory organs of both male and females changed expression of 1200 and 931 genes, respectively, as they aged and were exposed to repeated bouts of noise exposure. Only 39 genes were differentially expressed between the sexes for young locusts and 9 for aged and noise exposed auditory organs. In young locusts we found sex-differences in genes for juvenile hormone and proteins involved in egg production and catalysis of steroid hormones. The majority of sex differences in Müller's organ manifested as a function of stress with females upregulating more and downregulating less genes compared to males. We hypothesise that sex differences in auditory decline are due to differences in immune responses and metabolic processes.