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Living it up see slug style

It's tough being a sea slug

Sea Slug

Animals really do have a tough time. They can't just go to the supermarket and load up the car, or carry a bag full of shopping home. They have to go out and find their supper. This can very time consuming.

And it's very tough for herbivores (plant eaters) as they spend most of their waking life chomping on the green stuff in an effort to find enough energy. If you thought that was bad, carnivores (meat eaters) have to go through all the messy business of eating their neighbours. This is fine as long as your have lots of neighbours that can't run very fast and of course they aren't trying to eat you.

A celebrity lifestye

Wouldn't it be nice if you could spend your time swimming around in the sun having a nice time with your mates, without having to waste loads of your precious time doing the tedious eating thing!

Sea slugs are not looked upon as particularly glamorous or interesting animals. The sea slug diaries is a documentary that is unlikely ever to be made, which is a shame, because some sea slugs really have got the celebrity life style cracked. Fancy lying around in the sun all day? Easy! Just get yourself some chlorophyll and do the plant thing: make your own food!

Many years ago scientists noticed that some sea slugs were a lovely green colour, just like plants. When scientists looked more closely they realised that the same chemical that makes plants green was present in the sea slug: chlorophyll. This is the stuff that allows plants to do photosynthesis and make their own food. But how did it get there?

The lean, green chlorophyll-thieving machine

The sea slug elysia chlororotica is a bit of a bandit. It loves to suck out the innards of green algae and store it inside its body. This is what makes them look green: stolen chlorophyll. Once inside the sea slug's body it is used to do photosynthesis just like it did in the algae. This great for the sea slug as it cuts out the middle man. All the advantages of being a plant, loads of food when it's sunny, and the advantages of being an animal, it can swim around to look for a mate. Cool!

Life is for sunbathing.­..

Sun bathing Slug

New studies have shown that our sluggy friends are even cleverer than we thought. Not only do they nick the chlorophyll, but they also kidnap the organelles (chloroplasts) and the genes that make the chlorophyll in the first place. What they have is an entire stolen chemical factory working inside their bodies. They don't ever have to hunt algae again. All they need to do is sunbathe.

The coral farmers

Lots of animals, such as corals, have algae living within their bodies. They aren't really part of the coral, but they live in nooks and crannies that the coral manufacture for them. What coral actually does is cultivate the algae and exploit their ability to do photosynthesis. They are farmers, much like human farmers grow and exploit crops.

Sea slugs do it better

Sea slugs are altogether more sophisticated. Not only do they rob the algae of their organelles, but they have taken some of their genes as well. To keep the organelles working, just like factories, they need to be supplied with raw materials. The genes are used by the sea slugs to make the raw materials needed by the chloroplasts.

Sea slugs did the gene therapy thing first!

It turns out that not only have the sea slugs high jacked the algae genes, but they now have them built permanently into their own genome. It is possible to take a newly-born sea slug that has never seen algae and still find algae genes.

This is the first time a fusion of animal and plant material has ever been seen. Bacteria swap genes all the time- multicellular, highly complex life forms aren't supposed to be able to do this, but it seems they can. This may prove to be a very important discovery. What we have is nature using techniques that only genetic engineers had thought of. Gene therapy is not quite so new after all.

Challenging Darwin

Darwin's Drawings

Evolution is the foundation of nearly all biology. It has famously been represented as a tree with branches. Darwin himself was the first person to represent evolution like this. All living things developed from a single ancestor and produced separate branches. These branches never touched.

Mister sea slug may just be the first hint that evolution is not quite as straightforward as we thought. What if the tips of the branches can touch? Different fully-formed organisms could swap genes with each other. This could prove to be revolutionary and change our whole grasp of the evolutionary theory.

Ever wondered why viruses are so popular? Do a bit of lateral thinking!

The big questions:

What makes a plant a plant, and an animal an animal?

What is the evolutionary tree?

Can creatures steal each other's genes?

If creatures can borrow each other's genes, what effect does this have on our ideas about evolution?