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Hydrothermal animals

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A hydrothermal vent is a fissure in a planet's surface from which geothermally-heated water issues. Hydrothermal vents were first discovered in 1977 and are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers. Under the sea, hydrothermal vents may form features called black smokers. A more recent theory (see chart) speculates that these vents do not have a volcanic origin.

The areas around these hydrothermal vents teem with a wide variety of extraordinary organisms. The most extraordinary aspect is that these organisms differ from every other animal on earth in that they do not depend on the sun for their energy, directly or indirectly. They live on the energy and compounds coming from the vents, powered by the energy at the Earth's core, or by preying on those animals that do.

YETI CRAB Kiwa hirsuta
This crab was first observed in March 2005 by marine biologists using the research submarine Alvin to explore hydrothermal vents along the Pacific-Antarctic ridge, south of Easter Island. Because of its hairy legs, this animal was nicknamed the "Yeti crab," after the fabled Yeti, the abominable snowman of the Himalayas.

Exactly how the Yeti crabs fit into hydrothermal-vent ecosystems is still a mystery. Scientists saw the crabs eating mussels that were cracked open when a submersible landed on the seafloor. But they also saw Yeti crabs holding their hairy claws out over plumes of warm water from hydrothermal vents. Because the crab's arm hairs support large colonies of filamentous bacteria, the scientists speculated that the crabs might be "farming" the bacteria, perhaps as a source of food. These specialized bacteria live off of the hot, metal-rich hydrothermal fluids that issue from the vents. This is not as far-fetched as it sounds—at least two other crab species have similar habits. Alternatively, lacking eyes, the crabs may use their hairs (which are actually flexible, hair-like spines called setae) as tiny chemical and physical sensors that help them find food or mates in the deep sea.

DEEP-SEA HYDROTHERMAL VENT SNAIL Crysomallon squamiferum
The snail's foot is armored with iron-mineral scales. It is protected by scale-shaped sclerites composed of the iron sulfides greigite and pyrite. No other animal is known to use iron sulfides in this way. The snail's shell is unusual in that its structure is composed of three layers. The outer layer is made of the aforementioned iron sulfides. The middle layer is organic, and is also the thickest of the three.  The innermost layer is made of aragonite, a calcium mineral that is found in the shells of mollusks and various corals.

Each layer contributes to the effectiveness of the snail's shell in different ways. The middle organic layer appears to absorb the mechanical strain and energy generated by a squeezing attack (as by the claws of a crab), making the shell much tougher. The organic layer also acts to dissipate heat.

The US military is currently funding research on the armor of the snail in hopes of developing insights into new military  designs.

HYDROTHERMAL VENT SNAIL Alviniconcha sp.
Suiyo Seamount, Tokyo Hydrothermal Vent. This snail inhabits deep-sea hydrothermal vents and harbors chemoautotrophic symbionts in its gills. This individual is probably a new species, and only a single specimen has been discovered to date.

HYDROTHERMAL VENT OCTOPUS (Vulcanoctopus hydrothermalis)

Almost completely translucent, this octopus preys on crustaceans and other animals that live near the vents.

HYDROTHERMAL VENT EELPOUT FISH
Little is known about this hydrothermal vent eelpout fish. All science knows about is its diet  - they prey upon crustaceans that live down there like copepods and crabs.

THE POMPEII WORM (alvinella pompejana)
Named after the town destroyed by the eruption of Vesuvius in  79AD, this little creature is famous among biologists because it is the most heat-tolerant animal known to exist  – it lives buried in the sides of the hydrothermal vents and is thus regularly exposed to water temperatures up to 80 degrees Celsius/176 degrees Fahrenheit. To survive in such an extreme environment, the worm lives in a close symbiotic relationship with thermophilic  bacteria: scientists believe the bacteria on the worms’ backs act like firefighters’ blankets, shielding the worms from intermittent blasts  of hot, metal-rich water.

The worm lives in a tube with its foot in water of temperatures up to 80 degreees Celsius while its head is in much cooler water, around 20 degrees. It feeds the bacteria that protect it by excreting a mucus from glands on its back. It is possible the bacteria also help feed the worm.

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