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The natural world. Looking pretty for 3.5b years.

Green Genes, Sea-slugs, & Evolution

Green Genes, Sea-slugs, & Evolution

Author: Hugh Bollinger/Monday, February 9, 2015/Categories: natural history, marine life, environment

Photosynthesizing sea-slug, Elysia chlorotica  (credit: Patrick Krug, Marine Biological Laboratory)

Nudibranchs ,
those shell-less and often beautifully colored mollusks known as sea slugs, are cool marine creatures and getting even more 'cool' by the day. Unrelated reports offer fascinating biological insights that are important for ecological, genetic, and evolutionary reasons.

The  Hopkin's Sea Rose , is responding to warming seawater temperatures by moving northwards into tidal zones where they were previously unknown. These "canaries of the ocean" are offering insights into climate change in 'real time'. Likewise, another sea-slug has turned itself green by incorporating genetic material from an algae upon which it feeds. It may be a new path to enhanced evolution. Green is the color of chloroplasts in plants. These photosynthetic structures contains the green pigment chlorophyll, that exists in every plant on Earth from microscopic algae to giant sequoias. It is now the color or a nudibranch that feeds on green algae A video shows a slug as it eats algae:



How the mollusk turns "green" is amazing and could make the basis for a good SciFi novel if it weren't true.

Publishing in  The Biological Bulletin , researchers at the Marine Biological Lab in Woods Hole, MA have showed, by using advanced imaging techniques, they had detected an algal gene present in the sea slug’s chromosome. This gene makes an enzyme critical to the function of the photosynthetic chloroplasts, found in its algal food. Indeed, the research confirmed that several genes, needed to repair chloroplasts, are present on the sea-slug's chromosome. A
lead author on the study, Sidney Pierce, said.

“The gene is incorporated into the slug's chromosome and transmitted to the next generation. While the next sea-slug generation must take up chloroplasts anew from algae, the genes to maintain the chloroplasts are already present in the slug's genome.This biological adaptation is a mechanism for rapid evolution and when a successful transfer of genes between species occurs, evolution basically happens from one generation to the next rather than over an evolutionary time scale of thousands of years."

Typically we think about gene transfer during sexual recombination or via modern molecular biological techniques but the slugs have developed a way for "horizontal gene transfer" by incorporate entire segments of foreign DNA into their chromosomes. In the process the slugs may be showing a new avenue for evolutionary change by natural selection. This discovery may open a new door to study genetics and evolution in 'real time' and even novel approaches to manipulating outcomes.

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