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

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.

QTL-Based Evidence of Population Genetic Divergence in Male Territorial Aggressiveness of the Japanese Freshwater Threespine Stickleback

Territorial aggression is widespread across the animal kingdom and is expressed in diverse ecological and social contexts. In addition, there are marked variations in the degree of male reproductive territoriality within and between species. These differences are often attributed to genetic components. However, the evolutionary genetic mechanisms in wild animals are poorly understood. This study explored the genetic basis of divergent male territorial aggressiveness between two Japanese freshwater populations, Gifu (GF) and Tomakomai (TM), in the threespine stickleback, which is a well-known model system for both behavioral ecology and evolutionary genetics. First, our field survey indicated that the distribution of reproductive territories differed greatly across breeding habitats between the focal populations, and the density of reproductive territories was much greater in the GF population. Second, a one-on-one arena aquarium experiment on male-male combat using wild-caught and common-garden-reared males revealed that GF males were genetically more aggressive than TM males. Finally, we performed quantitative trait loci (QTL) analysis using an F2 hybrid cross between the two populations to identify the causal genomic regions contributing to the divergence in male territorial aggressiveness. Our QTL analysis identified a single significant locus in an aggression-related behavioral component, that is, the number of bites of focal F2 males toward a GF stimulus intruder. Two notable behavior-related genes, HTR2A and MAO-A, are found near this locus. These genes have often been suggested to influence of aggressive behavior in animals; therefore, they are regarded as important candidate genes for further functional analyses. Thus, we are the first to provide a QTL-based genetic basis for population divergence in male territorial aggressiveness in the threespine stickleback.

Association of serotonin system-related genes with homicidal behavior and criminal aggression in a prison population of Pakistani Origin

The serotonin transporter (SLC6A4), 5-HT_2A (HTR2A) and 5-HT_2B (HTR2B) recepter genes, express proteins that are important regulators of serotonin reuptake and signaling, and thereby may contribute to the pathogenesis of aggressive criminal behavior. 370 sentenced murderers in Pakistani prisons and 359 men without any history of violence or criminal delinquency were genotyped for six candidate polymorphisms in SLC6A4, HTR2A and HTR2B genes. An association of higher expressing L/L and L_A/L_A variants of the 5-HTTLPR polymorphism was observed with homicidal behavior (bi-allelic: OR = 1.29, p = 0.016, tri-allelic: OR = 1.32, p = 0.015) and in the murderer group only with response to verbal abuse (OR = 2.11, p = 0.015), but not with other measures of self-reported aggression. L/L and L_A/L_A genotypes of the 5-HTTLPR polymorphism were associated with higher aggression scores on STAX1 scale of aggression compared to lower expressing genotypes (S/S, S/L_G, L_G/L_G) in prison inmates. No associations were apparent for other serotonergic gene polymorphisms analyzed. Using the Braineac and GTEx databases, we demonstrated significant eQTL based functional effects for rs25531 in HTTLPR and other serotonergic polymorphisms analyzed in different brain regions and peripheral tissues. In conclusion, these findings implicate SLC6A4* HTTLPR as a major genetic determinant associated with criminal aggression. Future studies are needed to replicate this finding and establish the biologic intermediate phenotypes mediating this relationship.