Parental care is thought to evolve through modification of behavioral precursors, which predicts that the mechanistic changes occur in the genes underlying those traits. The duplicated gene system of oxytocin/vasopressin has been broadly co-opted across vertebrates to influence parenting, from a pre-duplication ancestral role in water balance. It remains unclear whether co-option of these genes for parenting is limited to vertebrates. Here, we experimentally tested for associations between inotocin gene expression and water balance, parental acceptance of offspring, and active parenting in the subsocial beetle Nicrophorus orbicollis, to test whether a single copy homologue, inotocin, has similarly been co-opted for parental care in a species with elaborate parenting. As expected, inotocin was associated with water balance in both sexes. Inotocin expression increased around sexual maturation in both males and females, although more clearly in males. Finally, we found that expression of inotocin was not associated with acceptance of larvae but was associated with a transition to male but not female parenting. Moreover, level of offspring provisioning behavior and gene expression were positively correlated in males but uncorrelated in females. Our results suggest a broad co-option of this system for parenting that may have existed prior to gene duplication, and that inotocin may be associated with flexibility in parenting behavior.

We conducted a large-scale experiment where we collected the heads of beetles of both sexes in social and non-social contexts to determine how gene expression of inotocin and inotocin receptor were associated with each context. This dataset contains data files that should allow replication of the analyses that link inotocin and inotocin receptor expression with different contexts associated with other homologs of the oxytocin/vasopressin system. The duplicated gene system of oxytocin/vasopressin has been broadly co-opted across vertebrates to influence parenting, from a pre-duplication ancestral role in water balance. The effects of oxytocin/vasopressin are often sex-specific, although oxytocin and vasopressin often “switch” which sex they act in across species, even for the same traits. Here, we experimentally tested for associations between inotocin gene expression and water balance, parental acceptance of offspring, and active parenting in the subsocial beetle Nicrophorus orbicollis, to test whether this single copy homolog of the oxytocin/vasopressin system, has similarly been co-opted for parental care in a species with elaborate parenting. Raw Ct values, - Delta Delta Ct, and relative expression values for gene expression data are provided in each context are provided.