January 9, 2013
http://news.nationalgeographic.com/news/2013/130109-shark-embryo-freeze-predator-animals-science/
Summary:
Recent studies show that embryonic sharks may freeze like a possum when they detect danger nearby. Sharks have the ability, using pores called the ampullae of Lorenzini, to sense the electrical fields that every living organism gives off. Ryan Kempster, a student at the University of Western Australia, conducted a study using 11 brownbanded bamboo shark embryos. He then simulated a weak electrical field that would represent the predator and recorded the reactions of the sharks. All the sharks stopped moving once they detected the electrical field. Normally, they would beat their tails back and forth so seawater could enter the embryo. However, this generates an odor as well as small currents. However, the sharks became used to the electrical field after the exact same signal was present again.
Relevance:
When we talked about evolution in class, Darwin proposed the idea of natural selection and survival of the fittest. This trait of "playing possum" is a beneficial trait and would give sharks that have it an edge over the ones that do not. Therefore, the sharks the have it are more likely to survive and pass their genes on to offspring, which is the idea of natural selection. Additionally, the sharks adapt to the signals after they have felt it once.
Are there any other species that have a similar adaptation? If so, is there any evidence that it evolved from a common ancestor?
ReplyDeleteThere are many species of organisms with this adaptation including certain species of snakes, other sharks, and of course the Virginia opossum. There is not any definitive evidence as these organisms have a varying ways of "playing dead".
DeleteDoes the freezing or seizing of the organism effect the normal cell development or any other common activities that a shark normally undergoes? I read that sharks needed to continue to swim in order to stay alive and functional, so does it affect that as well? This is interesting mainly because I haven't heard of it before.
ReplyDeleteIt apparently does not effect the cell development as this starts to occur when the shark is fully formed. Also, this state does not appear affect to the sharks in the embryos. Additionally, there are other species of sharks such as the lemon shark which can reach a tonic state. In that state, they essential "play dead" as a defense mechanism.
Delete