Thursday, February 27, 2014

Photosynthetic Animals?

Photosynthesis, the process by which an organism uses energy from the sun to make food, is commonly thought to only be in the domain of plants. However, it turns out that there are in fact some species of animals which are photosynthetic. This post will focus on one particularly amazing species, the sea slug Elysia chlorotica, and the mechanism by which it undergoes photosynthesis.
File:Elysia chlorotica (1).jpg
The sea slug Elysia chlorotica is, it turns out, not born with chloroplasts, the organelles necessary to do photosynthesis. It eats photosynthetic algae for sustenance, particularly when it is young, and somehow in the digestive process it extracts chloroplasts from the algae and incorporates them into its body. The chloroplasts function just as they do in the algae; they synthesize sugar, but this time the snail gets the benefit  instead of the algae!
What has relatively recently been discovered is that the snail actually produces its own chlorophyll to sustain the chloroplasts, using algal DNA that  it somehow incorporated into its genome. The DNA transfer necessary for that to happen (from algae to animal) is virtually unknown in the animal world, but  it  is  clear that it  happened in this case. Nature works in magnificent and mysterious ways, and Elysia chlorotica is certainly evidence  of that! 
-JE

8 comments:

  1. It is really impressive the degree to which some symbiotic organisms become intertwined. This is the kind of genetic modification that is currently being done by humans, so it is shocking to see such a successful implementation in a naturally occurring organism. That said, when it comes to the instability and mutability of DNA nothing should be all that surprising. DNA regulation mechanisms, especially in primitive organisms such as these, are not perfect and wild mutations such as this can occur and give us amazing creatures like Elysia chlorotica. Out of curiosity, where are the chloroplasts stored? Are they kept in the cytoplasm or in specialized pockets?

    -Stephen O'Brien

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    1. DNA mutation is not capable of everything. According to Lynn Margulis, the famous UMass professor who passed away two years ago, the most important driving force in evolution is symbiosis, the synthesis of two organisms into a meta organism. Elysia chlorotica is a good example of this, but so are the chloroplast and mitochondria, which originated as bacteria separate from the eukaryotic organisms that possess them.

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  2. I like this post a lot. I've never heard of this type of animal and the fact that it is photosynthetic. I found it most interesting that it is able to use algal DNA in order to be successful at photosynthesis and sustain the chloroplasts.

    Posted by Morgan Matuszko

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  3. This is amazing that Elysia can produce chloroplasts on its own. I think it is an example of horizontal gene transfer between Elysia and algae. Its is interesting that Elysia chlorotica has great posterior surface area. Could it be an evidence to show this gene transfer has occurred since a while ago?

    Posted by Yim Hui

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  5. It genetic mutations and discoveries that humans have yet to find are amazing; photosynthesis has so many applications for a greener world, and to find this ability in an animal is so exciting for that field. Such a great article and incredibly relevant to the current times.
    Nicole peterkin

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    1. The fact that this kind of endosymbiosis has been found in an invertebrate is an amazing thing, But I am skeptical that it could happen in an adult vertebrate. For one thing, verberates have a much more advanced immune system than invertebrates. Spotted salamanders were found to have algae inside their embryos, which helped the embryos hatch. But the algae seem to have disappeared when the salamanders became adults and their immune systems kicked in.
      -JE

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  6. Since the sea slug can incorporate the algae's DNA into its own, are the mechanisms that extract the chloroplasts already present within the species or do they occur as a result of the algae being incorporated into its body?

    posted by: Nicole Boisvert

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