The neural basis of tadpole transport in poison frogs

Abstract

Parental care has evolved repeatedly and independently across animals. While the ecological and evolutionary significance of parental behaviour is well recognized, underlying mechanisms remain poorly understood. We took advantage of behavioural diversity across closely related species of South American poison frogs (Family Dendrobatidae) to identify neural correlates of parental behaviour shared across sexes and species. We characterized differences in neural induction, gene expression in active neurons and activity of specific neuronal types in three species with distinct care patterns: male uniparental, female uniparental and biparental. We identified the medial pallium and preoptic area as core brain regions associated with parental care, independent of sex and species. The identification of neurons active during parental care confirms a role for neuropeptides associated with care in other vertebrates as well as identifying novel candidates. Our work is the first to explore neural and molecular mechanisms of parental care in amphibians and highlights the potential for mechanistic studies in closely related but behaviourally variable species to help build a more complete understanding of how shared principles and species-specific diversity govern parental care and other social behaviour.

Hormonal and neural correlates of care in active versus observing poison frog parents

“…Finally, we identified differentially expressed transcripts present in a collection of 158 transcripts of interest we previously compiled based on their known roles in parental care (Fischer et al, 2019).…”

“…We performed tissue processing and analysis of neural activity in sex-reversed transporting and non-transporting control females in a manner identical to that previously described for our comparison of neural activity during tadpole transport across three closely related species of poison frog, including D. tinctorius (Fischer et al, 2019). Briefly, we sectioned brains into four coronal series at 14µm.…”

“…Signaling, Danvers, MA, USA) and followed procedures standard in our lab for immunohistochemical procedures for 3',3'-diaminobenzadine (DAB) antibody staining. Detailed methodological descriptions are in (Fischer et al, 2019).…”

“…We quantified labeled cells from photographs using FIJI image analysis software (Schindelin et al, 2012). Brain regions were identified using our dendrobatid frog brain atlas (Fischer et al, 2019). We measured the area of candidate brain regions and counted all labeled cells in a single hemisphere for each brain region across multiple tissue sections.…”

“…We explored main effects of group, sex, and regional differences in further detail using post hoc comparisons Tukey adjusted for multiple hypothesis testing. We qualitatively compared neural activity differences during sex-reversed and sex-typical transport but did combine these data into a single analysis as sex-typical data are from a previously published study (Fischer et al, 2019) and were collected and processed at a different time.…”