Lobsters May Explain Aggression in Humans Usually, when people see lobsters they usually think of how nice they would taste with a side of butter sauce. What marine biologists have done, is use the lobster as a model organism to study the link between hormones and behavior. One reason for using lobsters is because they have giant neurons which fire very rapidly when triggered.
Biologists at Harvard have located the nerve cells that cause the release of serotonin, which causes the lobster for display aggressive behavior. Aggressive behavior usually consist of the lobster raising its claws, antennae, and standing tall attempting to make themselves look larger. The nerve cells that control submissive behavior have also been isolated. When octopamine is released the lobster crouches and lies flat.
The lobster's release of serotonin has been compared to the release of adrenaline in humans. Adrenaline is released when a frightening or threatening stimulus is presented to us. It is what causes the "Fight or Flight" response. Since lobsters display this same response through a similar pathway (chemical), it can provide a better understanding about how hormones work with the nervous system. Perhaps it will provide science with more clues to understanding the human body, and the resulting behaviors.
I work in a lab here at UMass with Professor Kunkel who is currently studying lobster shell disease. As a result, he maintains live lobsters. Each lobster is kept in a tank with up to seven or eight others. For Identification purposes and to protect them from each other, they are divided up into plexi-glass partitions. The lobsters are from various parts of New England and are all the same species, Homarus americanus. Lobsters are usually solitary, so when they are placed in a tank with others, they will fight until one lobster becomes dominant. Since I work there quite often, I figured it was a perfect opportunity to attempt to trigger some of the behaviors and record it for everyone. In the video you will see two lobsters. When they were first placed in the tank together they were constantly fighting. Now there seems to be a dominant lobster and a submissive lobster. You will also see the fixed action pattern, described on a early handout from class. The most interesting behavior (I thought) that I was able to record is at the beginning of the video. When the lobster was placed behind the plexi-glass partition it figured out how to move it, in order to pursue the other lobster through the partition. Can anyone suggest an experiment involving lobster behavior? Let me know what you think of the video.
Lobster Video by Me: Lobster Behavior
Source Article: Lobster Aggression
Update
Lobster sex can be determined externally by look for the presence of claspers (swimmerets) or the female slipper on the underside of the lobster's tail. This takes some practice. Prof. Kunkel has been away this week, so I was unable to ask him. As far as I can tell, the two lobster in the video are both male. I didn't investigate the sex of the third lobster that you see in the background. It is most likely that they are fighting over territory, rather than attempting to mate. (I could be wrong). The two lobsters had been in the tank for at least 2 months together, so I would assume they would have "known" each other by the time the video was made. According to Woods Hole research, lobsters are capable of recognizing individuals and remembering them, see HERE.
Lobsters display aggression towards both sexes. They show aggression towards females when mating as part of their reproductive and survival strategy. Aggression towards males if mainly territorial. I think lobster reacted to the net and the rake differently because they disturbed the water more. Lobster are very sensitive to motion. This quick motion of the large object stimulated the Flight response, which is the fixed action pattern that you saw. The green stick was placed slowly in the tank, isn't very large, and disturbed the water less. The lobsters were not threatened by the stick, therefore tried to fight it.
As far as the levels of octopamine or serotonin in lobsters, I would image it is a positive correlation. I would imagine more aggressive lobsters would have higher levels of serotonin, and submissive lobsters higher levels of octopamine. A study in 1980 shows that directly injecting the hormones in the lobsters causes the expected behaviors, see HERE.
Finally, because this research and article was conducted in the 80's, it has probably already helped us in the medical field. Technology allows us today to use more complex organisms, more closely related to humans. But, lobster still remain a good model for our learning purposes and understanding the the link between hormones and behavior.
If enough people are interested I would be glad to make a "Sequel" to the lobster video to test out some of your questions/experiments.
Contact: asceusa@bio.umass.edu
Posted by: Amanda Sceusa (5)
posted by PWH @ 8:06 PM
8 comments
8 Comments:
The video was well organized and depicted all the actions that you stated. During the fight or flight response, I wondered what the main lobster would do if you moved the green stick to another lobster. Would the lobster follow the green stick and continue the fight or flight response near the other lobster or do nothing? Was the lobster in the fight or flight response segment the dominant lobster?What are the sexes of the lobsters in the video?
Is there a hormonal difference in the levels of serotonin and octopamine between the dominant and submissive lobsters? I don't have an experiment involving lobster behavior, but I was thinking about differences in behaviors between dominant and submissive lobsters.
SUSAN DUONG
Great job on the video it looks like you put a lot of work into your post. I found it interesting to see how the lobsters reacted with their flight response. It looked like they used the same type of mechanism that the crayfish we talked about in class used. They curled their tail under their bodies in a fast motion in order to propel themselves backward to ensure a fast getaway.
I also wonder what the sexes of the lobsters that you are studying are. Will lobsters fight only another same sex lobster or any other lobster? And are lobsters aggressive generally all the time? I find it interesting that the lobster would go through the trouble of moving the partition in order to get to the other lobster in the tank.
A possible experiment could be to see which objects a lobster reacted to the most. Maybe an object that resembled one of it's predators. I just found it interesting how the lobster was aggresive towards going after the green object but had such an immediate flight response to the rake and net. I wonder why that is?
Posted by: Lindsay Goodyear (5)
This was done very well. The post talked about everything in the video. I was wondering if you've tried seperating the lobsters with anything besides see through glass? Perhaps in the absence of sight the lobsters might still be able to smell or sense the neighboring lobster. Also does gender have any meaning to whether or not dominance and submission is fought over?
Ada Marie Flores
very interesting video! is it only the males that fight or are the females aggressive as well? also, do males show higher levels of aggression toward other males in presence of a female?
-Hessom Minaei
Great video! The fact that we can learn something about ourselves from a lobster shows how many similarities we share with all life. It would be interesting to know if some or all of these aggressive behaviors were also used during mating periods and somehow linked through the release of serotonin.
Allan Eldridge
Nice article and video. I was curious as to how the lobsters determine who is the more dominant? You mentioned that serotonin is responsible for aggressive behavior but how does this help us understand how adrenaline is triggered in humans. Is it because their neurons are larger and easier to observe? Good luck on your experiments.
-Carlos A. Varela
Did these lobsters know each other before?
If not, the aggression may have been caused by just "Who dominates" like in other animals. When animals know each other and know who's stronger, they don't really get into fight many times. But they become very aggressive in newly formed groups or community until they decide who rules.
-Yi, Jeongsang
Very good footage in the video. The fixed action pattern appeared to be executed just as it was described prior in the animal behavior course. It is very interesting that the release of hormones in the lobsters can help us to gain information about the release of hormones in humans, but are there any new discoveries about hormonal response in humans due to these studies of lobsters? If so, does benefit the medical field at all?
-Kiel Boutelle
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