Now, methane gas can sometimes rise up from within the Earth's crust. If it pops up in water that's cold enough and of high enough pressure, the water forms a crystal that traps the methane within it. We now have methane clathrate, also known as fire ice. Why fire ice? Because it looks like ice and it can be set on fire!
But some creatures have found other ways of liberating this energy without just flaming it up. There are bacteria that can eat this fire ice, getting their energy from the methane. And, deep beneath the waves, there is a worm that eats this bacteria.
|Image: MacDonald, Texas A&M|
Not much is known about them, but they can survive some 4 days with almost no oxygen at all. Larvae are thrown into the currents and have about 3 weeks to find food before they die. It's a tough world down there!
One interesting thing is that this methane clathrate was once thought to exist only in the cold of the outer Solar System. We now know that it exists on Earth and can support not only bacteria, but multicellular organisms too. Space worms, anyone?