delete
01-27-2007, 12:20 PM
I was searching for some information about the sexlife of trout, (a fish) when I found this:
http://www.sebiology.org/Education/pageview.asp?S=6&mid=&id=308
Stress Management for Dummies
From bullies in the fish tank to lizards with black eyes, animals exhibit a startling range of behavioural and physiological responses to help them cope with stressful situations. The fact that stress is currently a hot topic in behavioural research was highlighted by the range of contributions on stress at this year's Annual Main Meeting in Edinburgh, of which a selection is presented here. Perhaps humans can pick up some top tips on stress management from the animal kingdom1,2,3?
Stress relief for bullies
Humans do it, primates do it - now fish have been found to do it too. New research on displaced aggression indicates that the central signalling systems controlling behavioural and endocrine stress responses may be highly evolutionarily conserved.
At last! An excuse for those of us who take our work-related stress out on our family. In humans and other primates, violent behaviour by victims of aggression is often directed towards an individual that was not the original source of provocation. Psychologists refer to this phenomenon as displaced aggression. Now researchers have discovered that dominant rainbow trout do the same thing: they reduce their stress levels by venting their frustration on socially subordinate animals. Writing in Hormones and Behavior, Dr. Øyvind Øverli and colleagues (University of Oslo) suggest that this method of stress reduction may be an evolutionarily conserved strategy, which may increase our understanding of violent aggressive behaviour in humans4.
“Rainbow trout are highly territorial animals” says Dr. Øverli “When a dominant fish harasses a subordinate, stress levels drop off quickly in the dominant animal but remain high in the subordinate. One possible explanation for this is that beating up a subordinate relieves stress.” To study the behavioural and endocrine effects of social stress, Dr. Øverli paired test fish with larger (dominant) and smaller (subordinate) fish. Test fish are first paired with a smaller, subordinate fish that they can beat up, then paired with a bigger fish that beat up the test fish, and finally put back with the subordinate fish (win - lose - win). A second group of test fish are paired with a subordinate, isolated, and then paired with the subordinate again (win - isolation - win), while a third group are subjected to a win-lose-isolation paradigm. “Test fish that suffer social defeat are far more aggressive when they are re-introduced to their subordinate partner” explains Dr. Øverli “In contrast, fish that are isolated between encounters with a subordinate show decreased levels of aggression when re-introduced to their smaller partner.”
Neuroendocrine analysis revealed that the presence of a socially subordinate fish inhibits the stress response of the test fish. The researchers assessed the levels of serotonin, a neurotransmitter that is involved in stress-related responses, and the level of the stress hormone cortisol in each fish. Interestingly, the test fish that were not re-introduced to their small partner exhibited elevated forebrain serotonin and plasma cortisol levels compared with test fish that had access to their partner after losing a fight. Like humans and other primates, these territorial fish appear to use displaced aggression as a stress coping mechanism.
Fish have personalities too
Dominant fish cause problems in aquaculture by eating more than their fair share of food and harassing subordinate animals, resulting in poor growth and high stress levels in subordinate fish. Scientists around Europe are examining the behaviour of farmed fish to identify new ways to improve the social environment and efficiency of aquaculture and fisheries.
Scientists have confirmed what you may always have suspected of your pet goldfish: fish have 'personalities'. Selective breeding of rainbow trout by Dr. Tom Pottinger (Centre for Ecology and Hydrology) has resulted in two lines with two distinctive stress coping styles or 'personality types'. So-called 'proactive' fish are more aggressive, are generally more active and are usually dominant over fish with a 'reactive' coping style, which tend to be passive and less active than 'proactive' fish. Dr. Svante Winberg (University of Uppsala) and his colleagues are interested in the relationship between stress responses and aggressive behaviour in these fish.
“A stress tolerant strain of fish is highly desirable for aquaculture” says Dr. Winberg “However, the problem is that stress tolerant fish are often also the most aggressive.” Dr. Winberg's group is part of an EU funded collaborative project involving scientists around Europe (The STRESSGENES project, coordinated by Dr. Patrick Prunet, INRA, France)5, which aims to identify candidate genes in fish associated with resistance to stressful conditions. Scientists hope that a better understanding of the biological mechanisms behind stress tolerance may inform new selection strategies and lead to practical benefits for aquaculture.
Once bitten, twice shy
Lobsters use cues in urine to distinguish between individuals. What's more, they can remember who they lost a fight to, giving them the opportunity to flee to fight another day.
Fish may only have a 3-second memory, but lobsters certainly don't. Professor Jelle Atema6's group at the Boston University Marine Program has discovered that when two lobsters fight, the loser remembers the winner and determines the intensity of a later fight when the two meet again.
Male lobsters can distinguish between individual opponents using the smell of their urine. To investigate how the lobsters use this information, Molly Steinbach7 sets up a 'boxing match' between two male lobsters, after which the 'nose' of either the loser or winner is disabled so they can no longer recognise their opponent. Perhaps surprisingly, Ms. Steinbach found that it is the loser who determines the intensity of subsequent fights, not the winner. During the fight, the researchers record a number of aggressive behaviours, from fleeing at one end of the scale to 'ripping and shredding' at the other.
Professor Atema's group found that when the loser's nose was disabled, the behaviour of both animals in the second fight was no different from their behaviour in the first fight. However, when the winner's nose was disabled but the loser's nose was intact, the second fight was shorter and less aggressive. “As soon as the loser catches a whiff of the winner, they back off. By recognising the winner of a previous fight and fleeing more quickly in their second fight, the losers receive less aggression from the winner” says Ms. Steinbach. The researchers hope to determine which cue in the urine enables individual recognition in the lobsters, and to establish the genetic basis for this cue.
Who knew he was the alpha male?
Anolis lizards show their fighting fitness through a colour signal on their face. New research indicates that dominant males are the ones that recover from stress and develop these colour signals fastest.
How do you know if a stranger will be nice or nasty? Professor Cliff Summers8' group at the University of South Dakota has found that you can predict the social status of male Anolis lizards before they fight. Wayne Korzan has discovered that how fast you recover from stress, to participate in feeding and courtship, foreshadows dominant social rank. Fast lizards are dominant lizards.
As in humans, when anoles are stressed their adrenaline levels shoot up. As well as causing the 'fight or flight' response, adrenaline results in black eyespots developing behind the lizards' eyes. In a fight, the male who develops these eyespots fastest is dominant and usually wins. When the researchers painted artificial black signals onto a male lizard, they found that other lizards became subordinate to the animal with fake eyespots.
The researchers are studying the effects of neurotransmitters that are involved in stress-related responses, such as dopamine and serotonin, to understand how these influence social behaviour. “Animals with high levels of dopamine in the regions of the brain that are involved in motivation and locomotion tend to win their fights” say Korzan and Summers; “Animals that initiate the stress response faster and recover from stress faster tend to win”. Conversely, animals with high levels of dopamine in the region of the brain associated with fear are usually subordinate and lose fights.
Anolis lizards may prove to be a useful model system for studying stress, aggression and depression in humans. The group hopes that a better understanding of the brain neurochemistry of these lizards may help the development of future treatments for stress and depression in humans.
http://www.sebiology.org/Education/pageview.asp?S=6&mid=&id=308
Stress Management for Dummies
From bullies in the fish tank to lizards with black eyes, animals exhibit a startling range of behavioural and physiological responses to help them cope with stressful situations. The fact that stress is currently a hot topic in behavioural research was highlighted by the range of contributions on stress at this year's Annual Main Meeting in Edinburgh, of which a selection is presented here. Perhaps humans can pick up some top tips on stress management from the animal kingdom1,2,3?
Stress relief for bullies
Humans do it, primates do it - now fish have been found to do it too. New research on displaced aggression indicates that the central signalling systems controlling behavioural and endocrine stress responses may be highly evolutionarily conserved.
At last! An excuse for those of us who take our work-related stress out on our family. In humans and other primates, violent behaviour by victims of aggression is often directed towards an individual that was not the original source of provocation. Psychologists refer to this phenomenon as displaced aggression. Now researchers have discovered that dominant rainbow trout do the same thing: they reduce their stress levels by venting their frustration on socially subordinate animals. Writing in Hormones and Behavior, Dr. Øyvind Øverli and colleagues (University of Oslo) suggest that this method of stress reduction may be an evolutionarily conserved strategy, which may increase our understanding of violent aggressive behaviour in humans4.
“Rainbow trout are highly territorial animals” says Dr. Øverli “When a dominant fish harasses a subordinate, stress levels drop off quickly in the dominant animal but remain high in the subordinate. One possible explanation for this is that beating up a subordinate relieves stress.” To study the behavioural and endocrine effects of social stress, Dr. Øverli paired test fish with larger (dominant) and smaller (subordinate) fish. Test fish are first paired with a smaller, subordinate fish that they can beat up, then paired with a bigger fish that beat up the test fish, and finally put back with the subordinate fish (win - lose - win). A second group of test fish are paired with a subordinate, isolated, and then paired with the subordinate again (win - isolation - win), while a third group are subjected to a win-lose-isolation paradigm. “Test fish that suffer social defeat are far more aggressive when they are re-introduced to their subordinate partner” explains Dr. Øverli “In contrast, fish that are isolated between encounters with a subordinate show decreased levels of aggression when re-introduced to their smaller partner.”
Neuroendocrine analysis revealed that the presence of a socially subordinate fish inhibits the stress response of the test fish. The researchers assessed the levels of serotonin, a neurotransmitter that is involved in stress-related responses, and the level of the stress hormone cortisol in each fish. Interestingly, the test fish that were not re-introduced to their small partner exhibited elevated forebrain serotonin and plasma cortisol levels compared with test fish that had access to their partner after losing a fight. Like humans and other primates, these territorial fish appear to use displaced aggression as a stress coping mechanism.
Fish have personalities too
Dominant fish cause problems in aquaculture by eating more than their fair share of food and harassing subordinate animals, resulting in poor growth and high stress levels in subordinate fish. Scientists around Europe are examining the behaviour of farmed fish to identify new ways to improve the social environment and efficiency of aquaculture and fisheries.
Scientists have confirmed what you may always have suspected of your pet goldfish: fish have 'personalities'. Selective breeding of rainbow trout by Dr. Tom Pottinger (Centre for Ecology and Hydrology) has resulted in two lines with two distinctive stress coping styles or 'personality types'. So-called 'proactive' fish are more aggressive, are generally more active and are usually dominant over fish with a 'reactive' coping style, which tend to be passive and less active than 'proactive' fish. Dr. Svante Winberg (University of Uppsala) and his colleagues are interested in the relationship between stress responses and aggressive behaviour in these fish.
“A stress tolerant strain of fish is highly desirable for aquaculture” says Dr. Winberg “However, the problem is that stress tolerant fish are often also the most aggressive.” Dr. Winberg's group is part of an EU funded collaborative project involving scientists around Europe (The STRESSGENES project, coordinated by Dr. Patrick Prunet, INRA, France)5, which aims to identify candidate genes in fish associated with resistance to stressful conditions. Scientists hope that a better understanding of the biological mechanisms behind stress tolerance may inform new selection strategies and lead to practical benefits for aquaculture.
Once bitten, twice shy
Lobsters use cues in urine to distinguish between individuals. What's more, they can remember who they lost a fight to, giving them the opportunity to flee to fight another day.
Fish may only have a 3-second memory, but lobsters certainly don't. Professor Jelle Atema6's group at the Boston University Marine Program has discovered that when two lobsters fight, the loser remembers the winner and determines the intensity of a later fight when the two meet again.
Male lobsters can distinguish between individual opponents using the smell of their urine. To investigate how the lobsters use this information, Molly Steinbach7 sets up a 'boxing match' between two male lobsters, after which the 'nose' of either the loser or winner is disabled so they can no longer recognise their opponent. Perhaps surprisingly, Ms. Steinbach found that it is the loser who determines the intensity of subsequent fights, not the winner. During the fight, the researchers record a number of aggressive behaviours, from fleeing at one end of the scale to 'ripping and shredding' at the other.
Professor Atema's group found that when the loser's nose was disabled, the behaviour of both animals in the second fight was no different from their behaviour in the first fight. However, when the winner's nose was disabled but the loser's nose was intact, the second fight was shorter and less aggressive. “As soon as the loser catches a whiff of the winner, they back off. By recognising the winner of a previous fight and fleeing more quickly in their second fight, the losers receive less aggression from the winner” says Ms. Steinbach. The researchers hope to determine which cue in the urine enables individual recognition in the lobsters, and to establish the genetic basis for this cue.
Who knew he was the alpha male?
Anolis lizards show their fighting fitness through a colour signal on their face. New research indicates that dominant males are the ones that recover from stress and develop these colour signals fastest.
How do you know if a stranger will be nice or nasty? Professor Cliff Summers8' group at the University of South Dakota has found that you can predict the social status of male Anolis lizards before they fight. Wayne Korzan has discovered that how fast you recover from stress, to participate in feeding and courtship, foreshadows dominant social rank. Fast lizards are dominant lizards.
As in humans, when anoles are stressed their adrenaline levels shoot up. As well as causing the 'fight or flight' response, adrenaline results in black eyespots developing behind the lizards' eyes. In a fight, the male who develops these eyespots fastest is dominant and usually wins. When the researchers painted artificial black signals onto a male lizard, they found that other lizards became subordinate to the animal with fake eyespots.
The researchers are studying the effects of neurotransmitters that are involved in stress-related responses, such as dopamine and serotonin, to understand how these influence social behaviour. “Animals with high levels of dopamine in the regions of the brain that are involved in motivation and locomotion tend to win their fights” say Korzan and Summers; “Animals that initiate the stress response faster and recover from stress faster tend to win”. Conversely, animals with high levels of dopamine in the region of the brain associated with fear are usually subordinate and lose fights.
Anolis lizards may prove to be a useful model system for studying stress, aggression and depression in humans. The group hopes that a better understanding of the brain neurochemistry of these lizards may help the development of future treatments for stress and depression in humans.