Project description:Individual stress coping style has profound effects on how animals respond to environmental change, and individuals within a population strikingly differ in how gene expression shifts in response to challenge. This study used a wild type Zebrafish (Danio rerio) population to: 1) identify and screen for individual coping style using a screening protocol for risk taking in groups and 2) do global transcriptomics of brains from proactive, reactive or randomly chosen individuals (n=10/group) under control conditions. Results show that within our population proactive and reactive individual coping styles can be accurately identified and may represent 10-30% of individuals within the population. Microarray data analyses identify fundamental differences between the three different groups where variance in gene expression values are reduced by using coping style as an explanatory variable. Furthermore, significant differences in mRNAs and related biological processes suggest that even under identical environmental conditions the molecular mechanisms that underpin physiological processes are very different between proactive and reactive individuals within a population. Experimental tank was an 18 litre glass aquarium (dimensions (LxWxH): 40 X 25 X 20cm) lined on three sides with white paper; the front wall was not covered to allow the observer to record the behaviour and divided at 1/3 of his length with a black PVC screen with a 3cm diameter hole in the middle. All the tank surfaces around this third area of the tank were covered with dark paper and closed on the upper part with a removable lid to provide a shelter for the animals. The hole was covered with the same PVC plastic material and removed once the screening started to allow the fish enter the novel environment. Food was not supplied the day before to ensure that during the test the fish were hungry and they had to make the decision to leave a safe area in order to forage. Boldness was measured as the time taken by individual fish to leave a group from a safe, darkened area. It hence represents the willingness of a fish to explore a new, potentially dangerous environment, or boldness. Tests were conducted with groups of 9 randomly-selected fish from stocking tanks. Fish were familiar to each other in the sense that they were previously held in the same stocking tank. Test started with a 10 min. habituation period in the sheltered area with the hole closed with a PVC screen and the top of the sheltered area of the tank also covered to provide a complete quiet place. Then the lid covering the hole was gently removed. Either the first 3 fish to exit the shelter or fish with latency times inferior to 10 minutes were considered bold fish and were removed gently with a fish net from the test tank and placed apart in another tank. Latency times of emergency from the sheltered area were recorded individually. Next 3 animals to emerge before 15 minutes were considered intermediate and also removed gently. At the end of this last 15 minutes, animals that still remained inside the sheltered area were considered shy. Intermediates were discarded and fish selected for different coping strategies where placed in different tanks for posterior molecular analysis. Selected animals were killed by an overdose of MS-22 and the brains were sampled. Individual tissue samples were homogenized into 0.3 ml of Tri-Reagent and stored at -80C for further molecular analysis.

Project description:Domesticated animal populations often show profound reductions in predator avoidance and fear-related behavior compared to wild populations. These reductions are remarkably consistent and have been observed in a diverse array of taxa including fish, birds, and mammals. Experiments conducted in common environments indicate that these behavioral differences have a genetic basis. In this study, we quantified differences in fear-related behavior between wild and domesticated zebrafish strains and used microarray analysis to identify genes that may be associated with this variation. Compared to wild zebrafish, domesticated zebrafish spent more time near the water surface and were more likely to occupy the front of the aquarium nearest a human observer. Microarray analysis of the brain transcriptome identified high levels of population variation in gene expression, with 1,749 genes significantly differentially expressed among populations. Genes that varied among populations belonged to functional categories that included DNA repair, DNA photolyase activity, response to light stimulus, neuron development and axon guidance, cell death, iron-binding, chromatin reorganization, and homeobox genes. Comparatively fewer genes (112) differed between domesticated and wild strains with notable genes including gpr177 (wntless), selenoprotein P1a, synaptophysin and synaptoporin, and acyl-CoA binding domain containing proteins (acbd3 and acbd4). Microarray analysis identified a large number of genes that differed among zebrafish populations and may underlie behavioral domestication. Comparisons with similar microarray studies of domestication in rainbow trout and canids identified sixteen evolutionarily or functionally related genes that may represent components of shared molecular mechanisms underlying convergent behavioral evolution during vertebrate domestication. However, this conclusion must be tempered by limitations associated with comparisons among microarray studies and the low level of population-level replication inherent to these studies. RNA was extracted from the brains of fish from four behaviorally distinct strains of zebrafish and hybridized on Affymetrix microarrays. Brains from 2-5 individual fish of the same sex were pooled and homogenized together, for a total of two biological replicate pools per sex per strain (16 microarrays total).

Project description:Domesticated animal populations often show profound reductions in predator avoidance and fear-related behavior compared to wild populations. These reductions are remarkably consistent and have been observed in a diverse array of taxa including fish, birds, and mammals. Experiments conducted in common environments indicate that these behavioral differences have a genetic basis. In this study, we quantified differences in fear-related behavior between wild and domesticated zebrafish strains and used microarray analysis to identify genes that may be associated with this variation. Compared to wild zebrafish, domesticated zebrafish spent more time near the water surface and were more likely to occupy the front of the aquarium nearest a human observer. Microarray analysis of the brain transcriptome identified high levels of population variation in gene expression, with 1,749 genes significantly differentially expressed among populations. Genes that varied among populations belonged to functional categories that included DNA repair, DNA photolyase activity, response to light stimulus, neuron development and axon guidance, cell death, iron-binding, chromatin reorganization, and homeobox genes. Comparatively fewer genes (112) differed between domesticated and wild strains with notable genes including gpr177 (wntless), selenoprotein P1a, synaptophysin and synaptoporin, and acyl-CoA binding domain containing proteins (acbd3 and acbd4). Microarray analysis identified a large number of genes that differed among zebrafish populations and may underlie behavioral domestication. Comparisons with similar microarray studies of domestication in rainbow trout and canids identified sixteen evolutionarily or functionally related genes that may represent components of shared molecular mechanisms underlying convergent behavioral evolution during vertebrate domestication. However, this conclusion must be tempered by limitations associated with comparisons among microarray studies and the low level of population-level replication inherent to these studies.

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Danio rerio

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