![New research has shown that Atlantic salmon (Salmo salar) experience a feeling akin to frustration when they are not given a reward they are expecting to receive - a response previously only observed in mammals and birds. Debates over the ethics of fishing often throw up questions of whether fish are ‘conscious’ and have an awareness of pain, which has fuelled a fair amount of research in the area. Fish have been shown to be capable of responding to classical conditioning and to have long-term memories; however, we are still unsure to what extent their cognitive abilities are linked to conscious moods and emotions. This concept was studied in the salmon using a model commonly used in mammalian research called omission of expected reward (OER). In these experiments, animals are conditioned to associate a certain stimulus with a positive reward, such as food, and are then subjected to the stimulus without receiving the reward to record how they react. In mammals, OER has consistently been shown to cause animals to become stressed and aggressive.Six groups, each consisting of 200 fish, were conditioned to associate a flashing light with feeding over a period of 22 days. By the end of this period, the fish showed attraction to the light due to association with the food reward, as opposed to their initial reaction of avoiding it. Three of the groups were then subjected to OER for 9 days - the fish were fed three times a day, and at two of these mealtimes, the expected food reward was delayed by 30 minutes. The other three groups carried on as normal, acting as controls.When the groups were compared, OER groups showed higher aggression and greater hierarchy, causing some individuals to grow more quickly at the expense of others - interestingly, even during the one meal a day when the reward was provided immediately, aggression levels remained high. Stress levels were measured by detecting the concentration of cortisol (a hormone which is involved in stress response) in the blood, but unlike the variation seen in aggressive behaviour, these were the same across all groups, suggesting that although there were behavioural signs of stress this did not translate to a physiological stress reaction.There are two possible explanations for the variation in aggressive behaviour:- Dominant individuals may be trying to keep their position for prime access to food in expectation of the coming reward- Aggression triggered by the stressful situation may be being displaced towards other individuals to help in coping with the conditions.In either case this leads to stronger hierarchy and more uneven distribution of resources, as was observed in this study. The overall conclusion is that fish respond behaviourally to frustrating conditions just like birds and mammals, suggesting this could be an adaptive response to unpredictable environments that has been conserved throughout vertebrate evolution. While we cannot yet conclude that fish definitely experience conscious emotional states, the results do highlight the importance of regular routine for domestic or farmed fish in order to reduce aggressive interactions between individuals that may be detrimental to the health of the population.Ref: Vinas M. A. et al., 2012. Omission of expected reward agitates Atlantic salmon (Salmo salar). Animal Cognition Online first [link]](http://25.media.tumblr.com/tumblr_m4t057BfDl1qkrbaho1_400.jpg)
New research has shown that Atlantic salmon (Salmo salar) experience a feeling akin to frustration when they are not given a reward they are expecting to receive - a response previously only observed in mammals and birds. Debates over the ethics of fishing often throw up questions of whether fish are ‘conscious’ and have an awareness of pain, which has fuelled a fair amount of research in the area. Fish have been shown to be capable of responding to classical conditioning and to have long-term memories; however, we are still unsure to what extent their cognitive abilities are linked to conscious moods and emotions. This concept was studied in the salmon using a model commonly used in mammalian research called omission of expected reward (OER). In these experiments, animals are conditioned to associate a certain stimulus with a positive reward, such as food, and are then subjected to the stimulus without receiving the reward to record how they react. In mammals, OER has consistently been shown to cause animals to become stressed and aggressive.
Six groups, each consisting of 200 fish, were conditioned to associate a flashing light with feeding over a period of 22 days. By the end of this period, the fish showed attraction to the light due to association with the food reward, as opposed to their initial reaction of avoiding it. Three of the groups were then subjected to OER for 9 days - the fish were fed three times a day, and at two of these mealtimes, the expected food reward was delayed by 30 minutes. The other three groups carried on as normal, acting as controls.
When the groups were compared, OER groups showed higher aggression and greater hierarchy, causing some individuals to grow more quickly at the expense of others - interestingly, even during the one meal a day when the reward was provided immediately, aggression levels remained high. Stress levels were measured by detecting the concentration of cortisol (a hormone which is involved in stress response) in the blood, but unlike the variation seen in aggressive behaviour, these were the same across all groups, suggesting that although there were behavioural signs of stress this did not translate to a physiological stress reaction.
There are two possible explanations for the variation in aggressive behaviour:
- Dominant individuals may be trying to keep their position for prime access to food in expectation of the coming reward
- Aggression triggered by the stressful situation may be being displaced towards other individuals to help in coping with the conditions.
In either case this leads to stronger hierarchy and more uneven distribution of resources, as was observed in this study.
The overall conclusion is that fish respond behaviourally to frustrating conditions just like birds and mammals, suggesting this could be an adaptive response to unpredictable environments that has been conserved throughout vertebrate evolution. While we cannot yet conclude that fish definitely experience conscious emotional states, the results do highlight the importance of regular routine for domestic or farmed fish in order to reduce aggressive interactions between individuals that may be detrimental to the health of the population.
Ref: Vinas M. A. et al., 2012. Omission of expected reward agitates Atlantic salmon (Salmo salar). Animal Cognition Online first [link]
blue-shark009:
My favorite animal is the water bear! They can survive extreme heat and cold, radiation levels, they can survive hundreds of years without food or water, and they can survive in space!! I think water bears beat koalas Hands down!
Ah, finally someone with a more unconventional favourite! And what a fabulous choice. There are hundreds of reasons why water bears (Tardigrada) are amazing animals. Tardigrades (meaning “slow walker” in Latin) are a phylum of over 1000 different species that are found everywhere in the world - from Himalayan peaks of over 6000 metres to ocean depths below 4000m, from icy polar regions to the heat of the tropics, in freshwater, saltwater and damp terrestrial habitats. If you’re wondering why such an abundant creature has so far escaped your notice, it’s because they are at their greatest 1.5mm and at their smallest, just 0.1mm long. But don’t dismiss them yet - they are most certainly one of the cutest and most interesting microscopic organisms out there!
Water bears have a body with four segments and four pairs of lobopodial (unjointed) legs each bearing a set of 4-8 little claws. They feed using a stylet, or small tube, with which they pierce plant or animal cells and then suck up the internal fluids. Of the many species of water bear, some are purely carnivorous, consuming bacteria, rotifers or other tardigrades, some are omnivorous, and some are herbivorous, eating only plant materials.
The most famous and interesting characteristic of water bears is that they can enter a state known as cryptobiosis if environmental conditions become insufficient to live in. In cryptobiosis, the tardigrade dries up into a form known as a ‘tun’ (containing less than 1% water) and its metabolic rate drops to a hundredth of a percent of its normal rate or may even be completely undetectable. It can remain like this for up to 100 years and only takes a few minutes to come ‘back to life’ once returned to favourable conditions! Cryptobiosis has a number of different triggers that activate slightly different pathways. These are drastic changes in water solute content such as ion concentration (osmobiosis), drought (anhydrobiosis), extreme temperatures (cryobiosis) or lack of oxygen (anoxybiosis). In their natural environment, the most common form of cryptobiosis is anhydrobiosis, but we’ve conducted all sorts of crazy experiments to see what else they can survive. They have sailed through several minutes at 151ºC, and several days below -200ºC. They can withstand extreme radiation at levels that would be lethal to almost all other animals. And tardigrades have even ventured into space, surviving 10 days of vacuum and cosmic radiation with 68% still retaining the ability to live and reproduce (the project is called TARDIS which just makes it all the better). Not only can they survive very low pressures as in the vacuum of space but also very high pressures, more than 1200 times greater than atmospheric pressure!
Finally, as with any great character the water bear even has its own cuddly toy. What more could you want from a favourite animal?!
Ref: Shifflett B. M., 2008. Tardigrades. University of Wisconsin Organismal Biology [link]
Lindahl K. & Balser S., 1999. Tardigrade Facts. Illinois Wesleyan University [link]
Goldstein B. & Blaxter M., 2002. Tardigrades. Current Biology 12(14):475. [link]
Wikipedia
![blue-shark009:
My favorite animal is the water bear! They can survive extreme heat and cold, radiation levels, they can survive hundreds of years without food or water, and they can survive in space!! I think water bears beat koalas Hands down!
Ah, finally someone with a more unconventional favourite! And what a fabulous choice. There are hundreds of reasons why water bears (Tardigrada) are amazing animals. Tardigrades (meaning “slow walker” in Latin) are a phylum of over 1000 different species that are found everywhere in the world - from Himalayan peaks of over 6000 metres to ocean depths below 4000m, from icy polar regions to the heat of the tropics, in freshwater, saltwater and damp terrestrial habitats. If you’re wondering why such an abundant creature has so far escaped your notice, it’s because they are at their greatest 1.5mm and at their smallest, just 0.1mm long. But don’t dismiss them yet - they are most certainly one of the cutest and most interesting microscopic organisms out there!Water bears have a body with four segments and four pairs of lobopodial (unjointed) legs each bearing a set of 4-8 little claws. They feed using a stylet, or small tube, with which they pierce plant or animal cells and then suck up the internal fluids. Of the many species of water bear, some are purely carnivorous, consuming bacteria, rotifers or other tardigrades, some are omnivorous, and some are herbivorous, eating only plant materials.The most famous and interesting characteristic of water bears is that they can enter a state known as cryptobiosis if environmental conditions become insufficient to live in. In cryptobiosis, the tardigrade dries up into a form known as a ‘tun’ (containing less than 1% water) and its metabolic rate drops to a hundredth of a percent of its normal rate or may even be completely undetectable. It can remain like this for up to 100 years and only takes a few minutes to come ‘back to life’ once returned to favourable conditions! Cryptobiosis has a number of different triggers that activate slightly different pathways. These are drastic changes in water solute content such as ion concentration (osmobiosis), drought (anhydrobiosis), extreme temperatures (cryobiosis) or lack of oxygen (anoxybiosis). In their natural environment, the most common form of cryptobiosis is anhydrobiosis, but we’ve conducted all sorts of crazy experiments to see what else they can survive. They have sailed through several minutes at 151ºC, and several days below -200ºC. They can withstand extreme radiation at levels that would be lethal to almost all other animals. And tardigrades have even ventured into space, surviving 10 days of vacuum and cosmic radiation with 68% still retaining the ability to live and reproduce (the project is called TARDIS which just makes it all the better). Not only can they survive very low pressures as in the vacuum of space but also very high pressures, more than 1200 times greater than atmospheric pressure!Finally, as with any great character the water bear even has its own cuddly toy. What more could you want from a favourite animal?!Ref: Shifflett B. M., 2008. Tardigrades. University of Wisconsin Organismal Biology [link]Lindahl K. & Balser S., 1999. Tardigrade Facts. Illinois Wesleyan University [link]Goldstein B. & Blaxter M., 2002. Tardigrades. Current Biology 12(14):475. [link]Wikipedia](http://24.media.tumblr.com/tumblr_m4ra57rV531qkrbaho1_400.jpg)
