Reception of conspecific cues alters testicular gene expression and improves fertility in boreal chorus frogs (Pseudacris maculata).

Evidence for the social modulation of reproduction in vertebrates is established but poorly defined for many taxa despite the link between social cues and endocrine function. It is unclear if physiological effects, such as increased sex hormone concentration or gamete maturation, impact reproductive outcomes, such as fertilization rates or viability of offspring. We investigated the effect of conspecific signals on the calling behaviour, reproductive output, and gonadal gene expression in the boreal chorus frogs (Pseudacris maculata). Using breeding trials in a captive setting, we found that broadcasts of conspecific calls nearly doubled the duration of calling activity and increased the proportion of viable eggs by over 13%. We then used RNA-sequencing techniques to demonstrate exposure to broadcasts of chorus behaviour increased the expression of genes associated with steroidogenesis, spermatogenesis, and gonadal development in the male chorus frogs within 6 h. Several gene pathways were similarly affected in the male chorus frogs receiving hormone injections to induce sperm development and release, implying there are parallels in hypothalamic-pituitary-gonadal axis stimulation induced by reception of conspecific cues and hormonal induction. We provide some of the first evidence of amphibian social signals causing rapid molecular changes linked to fertility regulation.