Sea slug has taken genes from algae it eats, allowing it to photosynthesize like a plant

Feb 12, 2015

Credit: Patrick Krug

By Science Daily

How a brilliant-green sea slug manages to live for months at a time “feeding” on sunlight, like a plant, is clarified in a recent study published in The Biological Bulletin.

The authors present the first direct evidence that the emerald green sea slug’s chromosomes have some genes that come from the algae it eats.

These genes help sustain photosynthetic processes inside the slug that provide it with all the food it needs.

Importantly, this is one of the only known examples of functional gene transfer from one multicellular species to another, which is the goal of gene therapy to correct genetically based diseases in humans.

“Is a sea slug a good [biological model] for a human therapy? Probably not. But figuring out the mechanism of this naturally occurring gene transfer could be extremely instructive for future medical applications,” says study co-author Sidney K. Pierce, an emeritus professor at University of South Florida and at University of Maryland, College Park.


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14 comments on “Sea slug has taken genes from algae it eats, allowing it to photosynthesize like a plant

  • Olgun Feb 13, 2015 at 4:38 am

    Is it the same gene that makes it look like a leaf?

    Not directly. The leaf shape is probably parallel evolution with selection favouring effective capture of sunlight.

    @OP – Importantly, this is one of the only known examples of functional gene transfer from one multicellular species to another,

    I thought some parasitic organisms transferred genes from the host.

    http://dash.harvard.edu/handle/1/5241355Host-to-parasite Gene Transfer in Flowering Plants: Phylogenetic Evidence from Malpighiales



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  • Not directly. The leaf shape is probably parallel evolution with
    selection favouring effective capture of sunlight.

    I am just wondering if the leaf shape, I am assuming, is the same as the plants found in the area with the same algae that not only transfers the gene to capture light but can nudge it in the right direction as far as shape goes. The green comes with the territory so I thought, why not the shape. Of course it all falls down when you take the caterpillar that looks like a bird dropping but It might be a way to accelerate local evolution and back the old saying of, ‘you are what you eat’. Just a thought.



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  • I suppose what I am saying is, can SOME sequences in genes be ‘contamination’ rather than mutation, which would entail Lamarckism, in a form, and rewrite the family tree of direct descendants.



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  • Olgun Feb 13, 2015 at 4:53 am

    *Not directly. The leaf shape is probably parallel evolution with
    selection favouring effective capture of sunlight.

    I am just wondering if the leaf shape, I am assuming, is the same as the plants found in the area with the same algae that not only transfers the gene to capture light but can nudge it in the right direction as far as shape goes.

    The chlorophyll in in flowering plants dates back to a symbiotic relationship millions of years ago. It has nothing to do with modern algae or animals like the sea-slug. Likewise the leaf shape and vascular system of flowering plants, evolved separately millions of years after chloroplasts.

    The green comes with the territory so I thought, why not the shape.

    .Vaucheria litorea is a species of yellow-green alga (Xanthophyceae).[2] It grows in a filamentous fashion (forming long tubular cells connected end to end)

    The alga does not grow leaves or have a leaf shape. It grows in long filaments.

    V. litorea are consumed by the sea slug Elysia chlorotica, but are only partially digested by them in order to retain the photosynthetic chloroplasts in a process called kleptoplasty. The sea slug feeds on V. litorea, retaining the chloroplasts in storage in cells along the slug’s digestive tract.[5][6] The chloroplasts continue to photosynthesize, providing energy to the slug, and contribute to the unusual coloration of the sea slug by their distribution throughout the extensively branched gut http://en.wikipedia.org/wiki/Vaucheria_litorea

    According to this link, the chloroplasts are absorbed intact from its gut, so the gene transfer must be some adaptation to keep them functioning and to metabolise the sugars created by photosynthesis.



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  • If I could do away with eating food and just photosynthesize enough energy for the cells I need to have, it’d be great. I don’t think photosynthesis would be packing on the fat. I might look like Kermit, but I’d be thin.



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