Giant Sea Spiders and How Antarctic Animals Cope With The Big Freeze

The Naked Scientists spoke to Prof. Lloyd Peck, British Antarctic Survey
13 March 2005

Interview with 

Prof. Lloyd Peck, British Antarctic Survey


Sea Spider - Pycnogonid


Lloyd - I'm a scientist who's interested in animals that live in extremely cold conditions. I work in Antarctica and look at some of the more unusual animals that live there in the sea, such as giant sea spiders that are larger than a dinner plate! I'm interested in their tolerance to the environment, and what the prospects are for these animals when the climate changes. I also like scuba diving under sea ice!

Chris - Have you got any evidence that things are already on the move?

Lloyd - There is a lot of evidence. The Antarctic Peninsula, which accounts for about 5% of the Antarctic continent, is possibly the fastest changing place on earth. The temperature has gone up by three degrees in 50 years. Most of Antarctica isn't changing, but on the peninsula we are seeing glaciers receding, ice shelves collapsing, plants growing where they never grew before, and the general ecology is changing. Fifty years is just a blink of an eye in geological time.

Chris - And is man causing this?

Lloyd - I think a lot of it is down to man. You can't discount some contribution from natural cycles and natural effects, but you just can't get away from the fact that man is changing the environment on earth.

Chris - Why is Antarctica such a special place?

Lloyd - Antarctica is different from most of the continents on earth as it's been isolated for 35 million years. This mean that the life in the seas has been isolated too. On top of that, Antarctica is one of the most seasonal places on the planet and has a very short summer season. In addition, the oceans are very stable between minus two and plus one degrees. It has been like this for millions of years, so you would expect the animals and plants that live there to be very very special. That's one of the reasons that I'm so interested in Antarctica because it's a special environment with special animals in it.

Chris - You'd think that the animals would be quite small because it's so cold.

Lloyd - If you look on the land, the animals are small. The biggest animals are 2 millimetre long mites! The reason life on land is so small is because the Antarctic terrestrial environment has only been about for a very short time and things have been pushed off by glaciations. In the sea, the environment has been around for a long time and the temperatures have been very stable. This has allowed animals to evolve to the environment very finely. What we find is that the environment puts limits on the size animals can grow. The limits are set by the amount of energy an animal can get in to use, and by the amount of oxygen in the water. As you can get more oxygen in the water the colder the water gets, the animals in Antarctica can get bigger. That's why we can get woodlice 5 inches long and sea gooseberries over half a metre long. We also have very large sea spiders.

Chris - What actually is a sea spider.

Lloyd - Scientifically, they're in the same major group of animals as terrestrial spiders and scorpions, but they live in the sea. In most places in the world, they are eight-legged like spiders on land. In Europe, the biggest ones are about 5 or 6 millimetres across. In Antarctica they have spread and formed many different sizes, including having 10 or 12 legs! However, they move very slowly and won't climb out of the ocean to attack you.

Chris - What do these animals do to stop themselves from freezing?

Lloyd - If you look at invertebrates such as sea spiders, anemones and starfish, they don't freeze because their body composition is the same salt concentration as the sea water around. So, they won't freeze as long as they stay away from the parts of the water that do freeze. Fish that live in the sea have slightly more dilute body concentration than the sea water around them. If their body temperature drops below about 0.6 degrees, they will freeze. In Antarctica, these fish have to have anti-freezes. In the early 1960s, the natural anti-freezes in fishes were discovered. Since then, companies have been trying to exploit them.

Chris - If you take these animals that are adapted to cold conditions and put them I warm water in a lab, do they die pretty quickly? For example, if sea temperatures are rising, is it pushing the margins for these guys?

Lloyd - One of the things concerning me most at the moment is if you warm up these Antarctic animals to plus 5 degrees, they will die in experiments. If you warm them up to 2 or 3 degrees, they lose the ability to do the things they need to live. Currently the top summer temperatures are about zero and plus one, so it doesn't need much of an increase to make it hard or impossible for these animals to feed properly or defend themselves against predators. They are therefore not very tolerant.


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