But maybe they soon will be - and it just might help solve future climate change issues. Archaea, a type of single-celled microorganism, perform many key ecosystem services including being involved with nitrogen cycling, and they are known to be the main mechanism by which marine methane is kept out of the atmosphere.
One of the basic questions scientists have asked is whether this life form could act as a food source for animals. To answer this, the researchers performed a laboratory study during which they fed two types of Archaea to worms, as well as meals of bacteria, spinach or rice, and the worms thrived on all of the food sources, growing at the same rate.
The finding of this new study adds a wrinkle to scientific understanding of greenhouse gas cycles.
The researchers were looking at biological life forms at a cold seep in the deep ocean off Costa Rica, when they opened up a rock and found worms living within the crevices. They found that the worms had been feeding on Archaea, which had, in turn, been consuming methane. They were able to trace the isotopic signature of the methane from the Archaea to the worms.
From what they learned from the Costa Rican study, the scientists also discovered that worms of the same family as those found in the rocks consume methane-munching Archaea at cold seeps off northern California and at Hydrate Ridge off the central Oregon coast, west of Newport. The researchers think the family of worms, the Dorvilleids, uses its teeth to scrape the Archaea off rocks.
The consumption of Archaea by grazers, a process coined as "archivory", is particularly interesting because the only way it could be documented was by tracing the isotopic biomarkers from the methane. When the researchers attempted to trace consumption of Archaea through lipid types and other mechanisms, they failed because the chemicals and proteins broke down within the worms.
"It could be that many other animals are consuming Archaea but we haven't been able to detect it," said Andrew Thurber, a post-doctoral researcher at Oregon State University and lead author on the study. "We still haven't found the right technique to identify animals that eat Archaea that don't rely on methane, but now we know to look. Hopefully, this will open up a lot of new research and provide a greater understanding of how the world works."
The deep ocean sequesters vast amounts of methane and researchers believe that Archaea consume a majority of it before it reaches the water column. The role of Archaea consumers now will have to be taken into effect, Thurber said.
"We're not yet sure of the implications," said Thurber. "But Archaea are found in many different places, from estuaries to the deep sea, so it is possible that they fit into food webs beyond the cold seeps where we documented the process."
Published online in the International Society for Microbial Ecology Journal.