Monoamine neurochemistry, behavior, and microhabitat contribute to male coquí frog modes: silent, territorial, and paternal

Abstract

Monoaminergic neurotransmitters are essential for a multitude of physiological and behavioral functions including territoriality and parental care. The Puerto Rican coquí frog, Eleutherodactylus coqui, possesses an intriguing multi-modal male behavioral organization whereby males can be territorial, paternal, and silent (non-calling). The objective of this study was to quantify central monoamines in the three male modes and integrate this neurochemistry with data from microhabitat shelter selection and male social structure. Males were assessed for monoamines and metabolites using high performance liquid chromatography with electrochemical detection. Results indicated that there are distinct and significant differences among the three male behavioral modes based on male social structure, microhabitat shelter selection, and neurochemistry. Silent males are non-combative, quiescent, occur nocturnally in relatively open locations with sparser vegetation, and are characterized by high levels of epinephrine and norepinephrine in several forebrain nuclei. Territorial males emit vocalizations, are typically surrounded by more vegetation than silent males, may have a silent male within their territory, and are denoted by significantly higher levels of norepinephrine in the preoptic area and ventral hypothalamus and dopamine in the amygdala responsible male territorial behaviors. Paternal males brood and guard developing embryos in secluded nest sites that are surrounded by vegetation, not within territories of residential males, and typically not in close proximity of silent males. Paternal brains have significantly higher levels epinephrine and serotonin in the raphe and reticular nuclei indicating the necessity to regulate metabolic processes and stress during the period of prolong paternal care.

Keywords: Eleutherodactylus coqui; Anuran; Monoamines; Paternal care; Silent males; Territoriality.