Tiny shrimps hold clues to alien life

A tiny shrimp residing at one of the world's deepest undersea hydrothermal vents holds clues about what life could be like on other planets, NASA scientists say.
Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, are studying a mysterious ecosystem in the Caribbean to get clues about what life could be like on other planetary bodies, such as Jupiter's icy moon Europa, which has a subsurface ocean.
"For two-thirds of the Earth's history, life has existed only as microbial life. On Europa, the best chance for life would be microbial," said Max Coleman, senior research scientist at JPL.
The particular bacteria in the vents are able to survive in extreme environments because of chemosynthesis, a process that works in the absence of sunlight and involves organisms getting energy from chemical reactions.

In this case, the bacteria use hydrogen sulphide, a chemical abundant at the vents, to make organic matter.
The temperatures at the vents can climb up to a scorching 400 degrees Celsius, but waters just an inch away are cool enough to support the shrimp.

The shrimp are blind, but have thermal receptors in the backs of their heads.
"The overall objective of our research is to see how much life or biomass can be supported by the chemical energy of the hot submarine springs," Coleman said.
Hydrogen sulphide is toxic to organisms in high concentrations, but the bacteria feeding the shrimp need a certain amount of this chemical to survive.

The shrimp position themselves on the very border between normal, oxygenated ocean water and sulphide-rich water so that they and the bacteria can coexist in harmony.
"It's a remarkable symbiotic system," Coleman said.
Scientists collected extensive specimens from two hydrothermal vent fields: The Von Damm field at 7,500 feet and Piccard at more than 16,000 feet, the world's deepest.
A bonus finding from studying this extreme oasis of life is that some of the shrimp, called Rimicaris hybisae, appear to be cannibalistic.
The researchers found that when the shrimp arrange themselves in dense groups, bacteria seem to be the main food supplier, as the shrimp likely absorb the carbohydrates that the bacteria produce.

But in areas where the shrimp are distributed more sparsely, the shrimp are more likely to turn carnivorous, eating snails, other crustaceans, and even each other.
Although the researchers did not directly observe Rimicaris hybisae practising cannibalism, scientists did find bits of crustaceans in the shrimps' guts. And Rimicaris hybisae is the most abundant crustacean species in the area.
"Whether an animal like this could exist on Europa heavily depends on the actual amount of energy that's released there, through hydrothermal vents," said Emma Versteegh, a postdoctoral fellow at JPL.