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Sunday, February 13, 2005

Riftia and Black Smokers: Review of Aliens of the Deep

We don't have to go to Mars, or Titan, to find amazing new life forms. What else is still undiscovered, under the sea, or in the tops of trees, or elsewhere?

Aliens of the Deep is an Imax movie. It lasts about 37 minutes, and is rated G. James Cameron, Director of Titanic, was deeply involved in making this movie. (Go here for the IMDB entry. All Movie Guide also has an entry on the film, but I can't link to it directly.)

I'm glad I saw this. Imax theaters aren't everywhere, and my wife and I were fortunate enough to be staying within 20 miles of one last weekend. Warning: We paid $8 each, at 11:30 in the morning, to see this, which was the senior rate.

The movie is about inhabitants of the ocean floor, and it features some spectacular views of the geology and biology of a small part of that. It also shows some wonderful animations of the four Galilean moons of Jupiter, and a (speculative) exploration of the ocean of Europa, one of those moons. Cameron used four diving vessels at once. He also used real scientists, apparently. One was an exobiologist, one a geologist of the ocean bottom, one was a marine biologist, and one a space scientist. No doubt they were carefully selected, but they seemed to be authentic. All of them, and some other crew, including Cameron, were shown during dives.

I was thrilled to see video of the black smokers found on the ocean floor about 30 years ago, and the living community that gets its energy from them. There were explanations of the geology and biology by the scientists. These communities do not get their energy from the sun, but from the heat of the water put out by the black smokers. Bacteria can use this heat as a source of energy, and other organisms consume the bacteria. The most exotic are the white and red tube worms, Riftia.

Some viewers will be upset with Cameron, who says that the black smoker community has been down there for a billion years. He also said that it will be there for another billion. (How could anyone possibly know that?) Some might be upset with the possibility that we might spend lots of money on a trip to Europa. However, the views of spectacular geology and biology should much more than make up for any upsets.

These undersea communities don't seem to have more than a handful of species in them. However, appearances may be deceiving. Bacteria live in the tubes of Riftia, and a report in Environmental Microbiology, in 2002 (not freely available) indicates that there are many such species, indicating many niches inside the tubes.

The black smokers are thought to be relatively short-lived. As a result, the organisms living around them must be able to disperse effectively. There has been a study of Riftia larval dispersal, in Nature in 2001 (not freely available) which indicates that larvae can travel up to about 100 km., depending on currents and other conditions.

I would like someone to try to find out how genetically homogenous each species in each community is. I'd also like to know how close the genes of populations of the same species, in different locations, are to each other. No doubt, eventually, someone will do research on these matters.

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