Octopamine Neuromodulation Regulates Gr32a-Linked Aggression and Courtship Pathways in \u3ci\u3eDrosophila\u3c/i\u3e Males

Chemosensory pheromonal information regulates aggression and reproduction in many species, but how pheromonal signals are transduced to reliably produce behavior is not well understood. Here we demonstrate that the pheromonal signals detected by Gr32a-expressing chemosensory neurons to enhance male aggression are filtered through octopamine (OA, invertebrate equivalent of norepinephrine) neurons. Using behavioral assays, we find males lacking both octopamine and Gr32a gustatory receptors exhibit parallel delays in the onset of aggression and reductions in aggression. Physiological and anatomical experiments identify Gr32a to octopamine neuron synaptic and functional connections in the suboesophageal ganglion. Refining the Gr32a-expressing population indicates that mouth Gr32a neurons promote male aggression and form synaptic contacts with OA neurons. By restricting the monoamine neuron target population, we show that three previously identified OA-FruM neurons involved in behavioral choice are among the Gr32a-OA connections. Our findings demonstrate that octopaminergic neuromodulatory neurons function as early as a second-order step in this chemosensory-driven male social behavior pathway

Experimental approaches to unravel proximate mechanisms of parasitoid searching and patch leaving behaviour

Animals exploit complex environments in an optimal way, often with limited brain capacities. Interestingly, it is largely unknown, how they do so. This thesis comprises five studies investigating proximate mechanisms modulating the searching behaviour of parasitoid wasps. These organisms serve as excellent organisms for such questions due to their tight link of searching success and fitness. While the first study assumed a simple motor response to serve as a heuristic, yet effective, mechanism, the remaining studies focussed on the role of octopamine [OA] and dopamine [DA]. Both substances being essential in the assessment of reward and aversive stimuli, respectively. Neither the assumed motor response could be met nor did OA or DA reveal any consistent effects with respect to the assessment of rewards and costs. DA slightly impacted the movement pattern. Treatment with OA revealed numerous effects, in total indicating an influence on stress level. Both is in line with studies on other species. Yet, although OA significantly influences searching behaviour, the underlying mechanism is considerably more complex than initially assumed. Last, it was shown that a generalisation on the basis of a few studies and stimuli with respect to the role of OA in the integration of rewards is a simplification

Sexual Dimorphism in Aggression: Sex-Specific Fighting Strategies Across Species

Aggressive behavior is thought to have evolved as a strategy for gaining access to resources such as territory, food, and potential mates. Across species, secondary sexual characteristics such as competitive aggression and territoriality are considered male-specific behaviors. However, although female–female aggression is often a behavior that is displayed almost exclusively to protect the offspring, multiple examples of female–female competitive aggression have been reported in both invertebrate and vertebrate species. Moreover, cases of intersexual aggression have been observed in a variety of species. Genetically tractable model systems such as mice, zebrafish, and fruit flies have proven extremely valuable for studying the underlying neuronal circuitry and the genetic architecture of aggressive behavior under laboratory conditions. However, most studies lack ethological or ecological perspectives and the behavioral patterns available are limited. The goal of this review is to discuss each of these forms of aggression, male intrasexual aggression, intersexual aggression and female intrasexual aggression in the context of the most common genetic animal models and discuss examples of these behaviors in other species.Fil: Pandolfi, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Scaia, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Fernandez, Maria Paz. Columbia University; Estados Unido

Octopamine Neuromodulation Regulates Gr32a-Linked Aggression and Courtship Pathways in Drosophila Males

Chemosensory pheromonal information regulates aggression and reproduction in many species, but how pheromonal signals are transduced to reliably produce behavior is not well understood. Here we demonstrate that the pheromonal signals detected by Gr32a-expressing chemosensory neurons to enhance male aggression are filtered through octopamine (OA, invertebrate equivalent of norepinephrine) neurons. Using behavioral assays, we find males lacking both octopamine and Gr32a gustatory receptors exhibit parallel delays in the onset of aggression and reductions in aggression. Physiological and anatomical experiments identify Gr32a to octopamine neuron synaptic and functional connections in the suboesophageal ganglion. Refining the Gr32a-expressing population indicates that mouth Gr32a neurons promote male aggression and form synaptic contacts with OA neurons. By restricting the monoamine neuron target population, we show that three previously identified OA-FruM neurons involved in behavioral choice are among the Gr32a-OA connections. Our findings demonstrate that octopaminergic neuromodulatory neurons function as early as a second-order step in this chemosensory-driven male social behavior pathway

Neuropharmocological Alterations of the Aggressive Behavior of Crayfish

Serotonergic-related compounds often facilitate aggression in various animals, including crayfish. However to date, studies have seldom shown the mechanism by which serotonergicrelated compounds alter aggressive behavior. It is assumed that serotonin changes the neurochemistry of those injected. In our study, we have attempted to report an observable mechanism by examining the communication system of crayfish. Crayfish use urine to communicate aggressive status, thus we analyzed the frequency of urine release from those injected with serotonergic-related compounds. For each trial, two size-matched crayfish, within 5% body weight, were allowed to interact after injection with serotonin, an agonist, an antagonist, or vehicle control. The concentration of all drugs was 3mM at a delivery dosage of 0.1ml/g. Aggressive interactions were recorded under black light to illuminate a fluorescein dye that was added to all injections. Urine release and aggressive behaviors were then analyzed

A Model for Basic Emotions Using Observations of Behavior in Drosophila

Emotion plays a crucial role, both in general human experience and in psychiatric illnesses. Despite the importance of emotion, the relative lack of objective methodologies to scientifically studying emotional phenomena limits our current understanding and thereby calls for the development of novel methodologies, such us the study of illustrative animal models. Analysis of Drosophila and other insects has unlocked new opportunities to elucidate the behavioral phenotypes of fundamentally emotional phenomena. Here we propose an integrative model of basic emotions based on observations of this animal model. The basic emotions are internal states that are modulated by neuromodulators, and these internal states are externally expressed as certain stereotypical behaviors, such as instinct, which is proposed as ancient mechanisms of survival. There are four kinds of basic emotions: happiness, sadness, fear, and anger, which are differentially associated with three core affects: reward (happiness), punishment (sadness), and stress (fear and anger). These core affects are analogous to the three primary colors (red, yellow, and blue) in that they are combined in various proportions to result in more complex “higher order” emotions, such as love and aesthetic emotion. We refer to our proposed model of emotions as called the “Three Primary Color Model of Basic Emotions.

Neuroecology of social organization in the Australasian weaver ant, Oecophylla smaragdina

The social brain hypothesis predicts that larger group size and greater social complexity select for increased brain size. In ants, social complexity is associated with large colony size, emergent collective action, and division of labor among workers. The great diversity of social organization in ants offers numerous systems to test social brain theory and examine the neurobiology of social behavior. My studies focused on the Australasian weaver ant, Oecophylla smaragdina, a polymorphic species, as a model of advanced social organization. I critically analyzed how biogenic amines modulate social behavior in ants and examined their role in worker subcaste-related territorial aggression. Major workers that naturally engage in territorial defense showed higher levels of brain octopamine in comparison to more docile, smaller minor workers, whose social role is nursing. Through pharmacological manipulations of octopaminergic action in both subcastes, octopamine was found to be both necessary and sufficient for aggression, suggesting subcaste-related task specialization results from neuromodulation. Additionally, I tested social brain theory by contrasting the neurobiological correlates of social organization in a phylogenetically closely related ant species, Formica subsericea, which is more basic in social structure. Specifically, I compared brain neuroanatomy and neurometabolism in respect to the neuroecology and degree of social complexity of O. smaragdina major and minor workers and F. subsericea monomorphic workers. Increased brain production costs were found in both O. smaragdina subcastes, and the collective action of O. smaragdina majors appeared to compensate for these elevated costs through decreased ATP usage, measured from cytochrome oxidase activity, an endogenous marker of neurometabolism. Macroscopic and cellular neuroanatomical analyses of brain development showed that higher-order sensory processing regions in workers of O. smaragdina, but not F. subsericea, had age-related synaptic reorganization and increased volume. Supporting the social brain hypothesis, ecological and social challenges associated with large colony size were found to contribute to increased brain size. I conclude that division of labor and collective action, among other components of social complexity, may drive the evolution of brain structure and function in compensatory ways by generating anatomically and metabolically plastic mosaic brains that adaptively reflect cognitive demands of worker task specialization and colony-level social organization

The decision to approach or avoid: Influence of social experiences during development on the establishment of consistent inter-individual differences and the role of neuromodulators in Gryllus bimaculatus

Intraspecific aggression is a widely distributed, highly plastic behaviour throughout the animal kingdom and serves to secure resources, as members of the same species compete for identical ecological niches. But the costs can rapidly exceed the advantages. Over the past years, the two-spotted Mediterranean field cricket, Gryllus bimaculatus, has emerged to a model organism for studying the mechanisms underlying aggressive behaviour. Crickets implement seemingly complex decisions via the action of well-known neuromodulators with analogues in vertebrates including humans. This study shows that an individual´s decision to approach or avoid an agonistic stimulus is mainly shaped by social experiences gathered during nymphal development and early adult life. In particular, the chronic subjugation of nymphs by adult males in the breeding colony and the absence thereof lead to the establishment of distinct behavioural ethotypes shifting the answer to the question of whether inter-individual differences are nature or nurture in favour of nurture. Individuality in adult behaviour can thus result from social experiences during development alone. Moreover, the decision to approach or avoid a potentially agonistic stimulus is differentially modulated by the actions of the neuromodulators octopamine, serotonin and nitric oxide, which are released in response to social interactions. Interestingly, the social status dependent predisposed response to an antennal stimulus can be altered by octopamine alone. Furthermore, the present study reveals that the nitridergic and serotonergic system play a major role in the assessment of agonistic signals.:1 Introduction ...................................................................................................... 1 2 Methods ............................................................................................................ 6 2.1 Experimental animals .................................................................................... 6 2.2 Experimental groups based on social experiences and isolation time .................................................................................. 8 2.3 Evaluation of dominance and subordination ......................................... 10 2.4 Multiple wins and defeats ...................................................................... 12 2.5 Contests against a hyper-aggressive opponent .................................... 13 2.6 The mandible threat display in response to antennal stimulation and feeding ............................................................................. 13 2.7 The priming effect .................................................................................... 14 2.8 Influence of food as a resource ............................................................... 14 2.9 Set up and video tracking ....................................................................... 15 2.10 Evaluation of exploratory behaviour ..................................................... 16 2.11 Response to a single antennal touch with an adult male´s antenna ..................................................................................................... 17 2.12 Pharmacological treatment ...................................................................... 18 2.13 Data analysis ............................................................................................. 20 3 Results ............................................................................................................ 22 3.1 Responses of nymphs and adults towards conspecifics ........................... 22 3.2 Mandible threat display and the mandible spread angle .......................... 24 3.3 Influence of dominance and subordination ................................................. 26 3.4 Influence of prior antennal stimulation (priming) .......................................... 28 3.5 Influence of priming coupled with CDM ...................................................... 30 3.6 Influence of food as a resource .................................................................... 30 3.7 Effects of different social experiences during nymphal development on adult behaviour ................................................................. 31 3.8 Turning responses as a reaction to a single antennal touch with an adult male´s antenna ....................................................................... 34 3.8.1 Short term isolates ............................................................................... 34 3.8.2 Long term isolates ............................................................................... 38 3.9 Effects of neuromodulatory drugs on behavioural elements in STI and LTI crickets ............................................................... 43 3.9.1 Aggression ............................................................................................ 43 3.9.2 General motility .................................................................................... 46 3.9.3 Turning responses ................................................................................. 50 3.9.3.1 Influence of octopaminergic drugs .................................... 50 3.9.3.2 Influence of nitridergic drugs ............................................... 53 3.9.3.3 Influence of serotonergic drugs .......................................... 58 4 Discussion .................................................................................................... 68 4.1 Nymphal interactions and their consequences for adult behaviour .......... 68 4.2 The decision to approach or avoid an agonistic stimulus ........................... 72 4.3 The role of neuromodulators released in response to social experience .... 77 4.4 Overall conclusion and outlook .................................................................... 84 5 Summary .......................................................................................................... 86 6 Zusammenfassung ........................................................................................... 91 7 References ........................................................................................................ 98 8 Appendix .......................................................................................................... 109 8.1 Figures and Tables .......................................................................................... 109 8.2 Publications and published abstracts ............................................................ 111 8.3 Curriculum vitae ............................................................................................ 113 8.4 Acknowledgments ......................................................................................... 11

MODULATING MALE AGGRESSION AND COURTSHIP: DETECTING EXTERNAL PHEROMONAL AND NUTRITIONAL INFORMATION

Survival and reproduction in the natural world requires an organism to identify and react to the presence of environmental stimuli in a time and cue dependent manner. Such temporal specificity requires the development and use of specialized sensory organs that receive this external sensory information. Neurons within the specialized sensory organs respond to touch, taste, pheromones, chemicals, and light, and transduce this information to the central brain. In many systems, gustatory and olfactory chemosensation in particular, provides critical information regarding sex and species identification as well as the status of food resources. The output of neurons which receive chemical information is regulated by the action of biogenic amines, including serotonin, dopamine, and norepinephrine. In this dissertation I examined the role of octopamine (the invertebrate structural homologue of norepinephrine) signaling in the regulation of two behaviors required for survival and reproduction; aggression and courtship. In chapter II, I, along with my colleagues, demonstrate that neurons bearing the taste receptor Gr32a form putative synapses with octopamine neurons within the subesophageal zone, and that octopamine neurons promote male aggression and courtship behavior. These findings help to explain how an organism selects appropriate behavioral responses when confronted with the pheromonal signals of a rival male. In chapter III, I examined the effects of octopamine signaling on taste sensitization. In this section, I examined the distribution and function of neurons that express the Oaβ1R receptor, and found that these neurons are sugar sensitive. As the presence of a food source is known to be a major contributor to the generation of aggressive and courtship behavior, these findings imply a mechanism by which exposure to an environmental stimulus or changes in internal octopamine signaling may sensitize a particular form of sensory input