Aggression is a common behavioral trait shared in many animals, including both vertebrates and invertebrates. However, the type and intensity of agonistic encounters and displays can vary widely both across and within...Aggression is a common behavioral trait shared in many animals, including both vertebrates and invertebrates. However, the type and intensity of agonistic encounters and displays can vary widely both across and within species, resulting in complicated or subjective interpretations that create difficulties in developing theoretical models that can be widely applied. The need to easily and objectively identify quantifiable behaviors and their associated morphologies becomes especially important when attempting to decipher the neurological mechanisms underlying this complex behavior. Monoamines, neuropeptides, and pheromones have been implicated as important neuromodulators for agonistic displays in both invertebrates and vertebrates. Ad- ditionally, recent breakthroughs in insect research have revealed exciting proximate mechanisms important in aggression that may be broadly relevant, due to the relatively high conservation of these neurochemical systems across animal taxa. In this review, we present the latest research demonstrating the importance of monoamines, neuropeptides, and pheromones as neuromodulators for aggression across a variety of insect species. Additionally, we describe the stalk-eyed fly as a model system for studying aggres- sion, which integrates physiological, morphological, and neurochemical approaches in exploring detailed mechanisms responsible for this common yet complex behavior. We conclude with our perspective on the most promising lines of future research aimed at understanding the proximate and ultimate mechanisms underlying aggressive behaviors .展开更多
Burying beetles Nicrophorus orbicollis exhibit facultative biparental care of young. To reproduce, a male-female burying beetle pair bury and prepare a small vertebrate carcass as food for its altricial young. During ...Burying beetles Nicrophorus orbicollis exhibit facultative biparental care of young. To reproduce, a male-female burying beetle pair bury and prepare a small vertebrate carcass as food for its altricial young. During a breeding bout, male and female behavior changes synchronously at appropriate times and is coordinated to provide effective care for offspring. Although the ecologicaJ and evolutionary factors that shape this remarkable reproductive plasticity are well characterized, the neuromodulation of parental behavior is poorly understood. Juvenile hormone levels rise dramat- ically at the time beetle parents accept and feed larvae, remain highly elevated during the stages of most active care and fall abruptly when care is terminated. However, hormonal fluctuations alone cannot account for this elaborate control of reproduction. The biogenic amines octopamine （OA）, dopamine （DA）, and serotonin （5-HT） mediate a diversity of insect reproductive and social behav- iors. In this study, we measured whole brain monoamine levels in individual male and female bury- ing beetles and compared OA, DA, and 5-HT profiles between breeding （parental） and nonbreed- ing, unmated beetles. Remarkably, after 24 h of care, when parental feeding rates begin to peak, DA brain levels increase in breeding beetles when compared to nonbreeding controls. In contrast, brain OA and 5-HT levels did not change significantly. These results provide the first evidence for a potential role of DA in the modulation of burying beetle parental behavior.展开更多
Ant colonies self-organize to solve complex problems despite the simplicity of an individual ant＇s brain. Pavement ant Tetramorium caespitum colonies must solve the problem of defending the ter- ritory that they patr...Ant colonies self-organize to solve complex problems despite the simplicity of an individual ant＇s brain. Pavement ant Tetramorium caespitum colonies must solve the problem of defending the ter- ritory that they patrol in search of energetically rich forage. When members of 2 colonies randomly interact at the territory boundary a decision to fight occurs when： 1） there is a mismatch in nest- mate recognition cues and 2） each ant has a recent history of high interaction rates with nestmate ants. Instead of fighting, some ants will decide to recruit more workers from the nest to the fighting location, and in this way a positive feedback mediates the development of colony wide wars. In ants, the monoamines serotonin （5-HT） and octopamine （OA） modulate many behaviors associated with colony organization and in particular behaviors associated with nestmate recognition and ag- gression. In this article, we develop and explore an agent-based model that conceptualizes how in- dividual changes in brain concentrations of 5-HT and OA, paired with a simple threshold-based de- cision rule, can lead to the development of colony wide warfare. Model simulations do lead to the development of warfare with 91% of ants fighting at the end of 1 h. When conducting a sensitivity analysis, we determined that uncertainty in monoamine concentration signal decay influences the behavior of the model more than uncertainty in the decision-making rule or density. We conclude that pavement ant behavior is consistent with the detection of interaction rate through a single timed interval rather than integration of multiple interactions.展开更多
Accurate assessment of the probability of success in an aggressive confrontation with a conspecific is critical to the survival and fitness of the individuals. Various game theory models have examined these assessment...Accurate assessment of the probability of success in an aggressive confrontation with a conspecific is critical to the survival and fitness of the individuals. Various game theory models have examined these assessment strategies under the assumption that contests should favor the animal with the greater resource-holding potential （RHP）, body size typically being the proxy. Mutual assessment asserts that an individual can assess their own RHP relative to their opponent, allowing the inferior animal the chance to flee before incurring unnecessary costs. The model of self-determined persistence, however, assumes that an individual will fight to a set personal threshold, independ- ent of their opponent＇s RHP. Both models have been repeatedly tested using size as a proxy for RHP, with neither receiving unambiguous support. Here we present both morphological and neuro- physiological data from size-matched and mismatched stalk-eyed fly fights. We discovered differ- ing fighting strategies between winners and losers. Winners readily escalated encounters to higher intensity and physical contact and engaged in less low-intensity, posturing behaviors compared with losers. Although these fighting strategies were largely independent of size, they were associ- ated with elevated levels of 5-HT. Understanding the neurophysiological factors responsible for mediating the motivational state of opponents could help resolve the inconsistencies seen in cur- rent game theory models. Therefore, we contend that current studies using only size as a proxy for RHP may be inadequate in determining the intricacies of fighting ability and that future studies investigating assessment strategies and contest outcome should include neurophysiological data.展开更多
文摘Aggression is a common behavioral trait shared in many animals, including both vertebrates and invertebrates. However, the type and intensity of agonistic encounters and displays can vary widely both across and within species, resulting in complicated or subjective interpretations that create difficulties in developing theoretical models that can be widely applied. The need to easily and objectively identify quantifiable behaviors and their associated morphologies becomes especially important when attempting to decipher the neurological mechanisms underlying this complex behavior. Monoamines, neuropeptides, and pheromones have been implicated as important neuromodulators for agonistic displays in both invertebrates and vertebrates. Ad- ditionally, recent breakthroughs in insect research have revealed exciting proximate mechanisms important in aggression that may be broadly relevant, due to the relatively high conservation of these neurochemical systems across animal taxa. In this review, we present the latest research demonstrating the importance of monoamines, neuropeptides, and pheromones as neuromodulators for aggression across a variety of insect species. Additionally, we describe the stalk-eyed fly as a model system for studying aggres- sion, which integrates physiological, morphological, and neurochemical approaches in exploring detailed mechanisms responsible for this common yet complex behavior. We conclude with our perspective on the most promising lines of future research aimed at understanding the proximate and ultimate mechanisms underlying aggressive behaviors .
文摘Burying beetles Nicrophorus orbicollis exhibit facultative biparental care of young. To reproduce, a male-female burying beetle pair bury and prepare a small vertebrate carcass as food for its altricial young. During a breeding bout, male and female behavior changes synchronously at appropriate times and is coordinated to provide effective care for offspring. Although the ecologicaJ and evolutionary factors that shape this remarkable reproductive plasticity are well characterized, the neuromodulation of parental behavior is poorly understood. Juvenile hormone levels rise dramat- ically at the time beetle parents accept and feed larvae, remain highly elevated during the stages of most active care and fall abruptly when care is terminated. However, hormonal fluctuations alone cannot account for this elaborate control of reproduction. The biogenic amines octopamine （OA）, dopamine （DA）, and serotonin （5-HT） mediate a diversity of insect reproductive and social behav- iors. In this study, we measured whole brain monoamine levels in individual male and female bury- ing beetles and compared OA, DA, and 5-HT profiles between breeding （parental） and nonbreed- ing, unmated beetles. Remarkably, after 24 h of care, when parental feeding rates begin to peak, DA brain levels increase in breeding beetles when compared to nonbreeding controls. In contrast, brain OA and 5-HT levels did not change significantly. These results provide the first evidence for a potential role of DA in the modulation of burying beetle parental behavior.
文摘Ant colonies self-organize to solve complex problems despite the simplicity of an individual ant＇s brain. Pavement ant Tetramorium caespitum colonies must solve the problem of defending the ter- ritory that they patrol in search of energetically rich forage. When members of 2 colonies randomly interact at the territory boundary a decision to fight occurs when： 1） there is a mismatch in nest- mate recognition cues and 2） each ant has a recent history of high interaction rates with nestmate ants. Instead of fighting, some ants will decide to recruit more workers from the nest to the fighting location, and in this way a positive feedback mediates the development of colony wide wars. In ants, the monoamines serotonin （5-HT） and octopamine （OA） modulate many behaviors associated with colony organization and in particular behaviors associated with nestmate recognition and ag- gression. In this article, we develop and explore an agent-based model that conceptualizes how in- dividual changes in brain concentrations of 5-HT and OA, paired with a simple threshold-based de- cision rule, can lead to the development of colony wide warfare. Model simulations do lead to the development of warfare with 91% of ants fighting at the end of 1 h. When conducting a sensitivity analysis, we determined that uncertainty in monoamine concentration signal decay influences the behavior of the model more than uncertainty in the decision-making rule or density. We conclude that pavement ant behavior is consistent with the detection of interaction rate through a single timed interval rather than integration of multiple interactions.
文摘Accurate assessment of the probability of success in an aggressive confrontation with a conspecific is critical to the survival and fitness of the individuals. Various game theory models have examined these assessment strategies under the assumption that contests should favor the animal with the greater resource-holding potential （RHP）, body size typically being the proxy. Mutual assessment asserts that an individual can assess their own RHP relative to their opponent, allowing the inferior animal the chance to flee before incurring unnecessary costs. The model of self-determined persistence, however, assumes that an individual will fight to a set personal threshold, independ- ent of their opponent＇s RHP. Both models have been repeatedly tested using size as a proxy for RHP, with neither receiving unambiguous support. Here we present both morphological and neuro- physiological data from size-matched and mismatched stalk-eyed fly fights. We discovered differ- ing fighting strategies between winners and losers. Winners readily escalated encounters to higher intensity and physical contact and engaged in less low-intensity, posturing behaviors compared with losers. Although these fighting strategies were largely independent of size, they were associ- ated with elevated levels of 5-HT. Understanding the neurophysiological factors responsible for mediating the motivational state of opponents could help resolve the inconsistencies seen in cur- rent game theory models. Therefore, we contend that current studies using only size as a proxy for RHP may be inadequate in determining the intricacies of fighting ability and that future studies investigating assessment strategies and contest outcome should include neurophysiological data.
