Green with Envy

The aquatic slug, Elysia chlorotica, makes a bloke go green with envy. And one day, when we need to eat algae based substitutions out of a tube, he could make us all be able to go a little green after a feed. Then we will be able to get some of our body’s energy from the sun. By next century, it might even be called a little old fashioned genetic engineering.

Reported by CSIRO E-Science.
If you had a pair of boxes labelled ‘plant’ and ‘animal’, how challenging would it be to find items to put in each of them? Easy, you’d say! A frog could go into ‘animal’ because it chases and eats flies. You could put a daisy into the ‘plant’ box because it gets energy by absorbing light and not other organisms.
Where would you put the aquatic slug, Elysia chlorotica? Well, it’s a slug, so you’d assume it would get its energy by eating algae or plant material. Obviously it’s an animal. Yet its dusky green colouration reveals quite an interesting trick – this slippery gastropod can also soak up the sun to feed itself.
Chloroplasts are tiny cell organs (or ‘organelles’) typically found in plants and algae. The green pigment in chloroplasts, called chlorophyll, absorbs light and uses it to bond water with carbon dioxide to form glucose, which is an energy source used by both plants and animals.
Many animals share their tissues and immediate surroundings with microbes that can photosynthesize. Coral, for instance, shelter helpful algae called zooxanthellae in exchange for nutrients.
But the strange E.chlorotica slug goes one step further – it has a digestive system that steals the chloroplasts from the algae it eats and tucks them away in special cells inside its own body.
Unfortunately for the slug, these chloroplasts break down as the chlorophyll and other proteins get used up. No matter – E.chlorotica has done the extraordinary. It has also stolen some of the algae’s DNA to make necessary repairs.
It’s not uncommon for bacteria to swap genes. Yet this is a rare example of an animal stealing the genes of a plant to help it survive.
Imagine if making dinner was as easy as a walk in the park.

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