Extreme worms

11 December 2010

Giant tube worms cope with many extremes in their homes on deep ocean black smokers.

Sarah - One of my all-time favourite species in the whole ocean is a kind of deep sea tube worm called Riftia.

Giant tube wormThey live at the deep sea vents in the middle of the Pacific ocean which can be up to several miles below the sea surface. They look a bit like giant lip sticks. They can grow up to 3m long, and they have this hard white outer tube and this beautiful bright red plume sticking out.

And they're actually an evolutionarily ancient lineage because there are examples in the fossil record dating back to at least the Cambrian which is over 500 million years ago.

The thing that I think makes Riftia special is that its got so many amazing adaptations to living in what we would think of as a really inhospitable environment down there at these hydrothermal vents. There's such high concentrations of toxic nitrates, hydrogen sulphides and really high heat levels.

First of all, let's think about how they get their energy. Down at this depth there's no sunlight so there's no photosynthesis which is how most food chains elsewhere in the oceans begins, which photosynthesizing species like algae and phytoplankton using sunlight to make sugars. So how do Riftia survive?

They have a symbiotic relationship with a type of bacteria that can convert the chemicals spewing out of these black smokers like HS into organic molecules that provide energy for the worms by a process called chemosynthesis.

The worms them absorb these nutrients directly into their tissues so technically they don't actually eat anything which is actually quite an unsual thing for an animal, not to eat, it's able to absorb its nutrients, especially for something that size.

The worms also have a high tolerance for concentrations of sulphides and nitrates that would be deadly to most other animals. The deep rich red colour of their plumes comes from haemoglobin which is the same sort of molecule that makes our blood red but their haemoglobin is differently structured and it's able to withstand high levels of sulphide still allowing it to carry oxygen around the worms body.

They're also the fastest growing marine invertebrate. They can grow nearly 2m in less than 2 years.

But because they live at such depth there's not that much known about them and it means that there's always more being discovered about them.

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