Creatures with weird features!
Since the discovery of hydrothermal vents in 1977, scientists have found
more than 500 organisms that had never been seen before. To live at
the vents, many of these organisms have unusual adaptations that were
new to scientists.
Let's learn more about these creatures.
Photo
by Dr. W. Jack Jones/EPAThe heat-loving ancient ones
Archaea means “ancient ones,” because scientists suspect they existed when Earth was very young and conditions on the planet were very harsh. Some Archaea have adapted to survive at 113oC (235oF)—temperatures scientists once thought too high for life to exist. These are called “hyperthermophiles,” or “high heat lovers.”
Starting with the smallest organisms, scientists found bacteria that use sulfur and methane (both of which are poisonous to oxygen-breathing animals) for energy. They also found other chemosynthetic organisms that were single-celled like bacteria, but turned out to be as genetically different from bacteria as bacteria are from trees. These were called Archaea, and they are now recognized as a completely separate kingdom of life. The second kingdom is “Bacteria.” The third is “Eukaryotes” (organisms with cells that have nuclei), which ranges from single-celled paramecia to human beings.
Photo courtesy of Richard Lutz, Rutgers and William Lange, WHOI
"Symbiosis is a close ecological relationship between the individuals of two (or more) different species. Sometimes a symbiotic relationship benefits both species, sometimes one species benefits at the other's expense, and in other cases neither species benefits -- John R. Meyer, Department of Entomology, NC State University
Clearly, the tubeworms receive nutrition from the bacteria. But the bacteria get something, too. The worms give the bacteria a cozy surface to grow on. Such a cooperative relationship between two organisms is called symbiosis. And one of the weirdest kinds of symbiosis was discovered in the red-plumed tubeworms, which initially mystified scientists because it had no mouth or stomach. How did it eat?
Scientists found a vent worm that lives in tubes on the sides of scalding black-smoker chimneys. These worms are called Alvinella pompejana (named partly after Alvin), or “Pompeii” worms. They may survive for short periods of time in vent water with temperatures up to 80°C (175°F). Scientists think the worms stay near the sulfur-rich vent fluids to encourage chemosynthetic bacteria to grow on them. The worms use their own bodies like “farms” to grow bacteria that they “harvest” and eat!
Photo: (left) Tubeworms absorb nutrients from seawater with their red-tipped plumes.
(Photo by Dudley Foster, WHOI)
(right) These nutrients feed chemosynthetic bacteria that live inside them.
The mystery of the worms with
no mouths
The first specimens of 6-foot-long tubeworms from the
1979 Galápagos cruise were given to Meredith Jones, a worm specialist
at the Smithsonian Institution, who carefully dissected them. He called
them Riftia pachyptila, or “thick-plumed rift worm.”
At a lecture at Harvard University in March of 1980, Jones described his ongoing work on the tubeworms. Among other things, he noted that he had found tiny sulfur crystals inside the tubeworms. A first-year graduate student named Colleen Cavanaugh (now a professor at Harvard) stood up and suggested a radical idea. The tubeworms, she said, were feeding on bacteria that they grew inside of them—an internal farm!
It turned out to be true. When Jones collected specimens
of very young tubeworms, he found that they had mouths. As teen-agers,
the tubeworms take in sulfur-eating bacteria. As they grow up, their
mouths disappear. The tubeworms’ feather-like red plumes act
as gills. They absorb oxygen from seawater and hydrogen sulfide from
vent fluids. The oxygen and hydrogen sulfide nourish the bacteria inside
the tubeworms. The tubeworms get a steady supply of bacteria to feed
on.
Tubeworms have a special type of hemoglobin cells in their blood that can transport
oxygen as well as sulfide (human hemoglobin only transports oxygen). Tubeworms’ hemoglobin
carries away sulfide products made by the bacteria, which would otherwise poison
the tubeworms.
Both the tubeworms and the bacteria living inside of them get something from this unusual arrangement, which is called endosymbiosis (from “endo,” meaning “inside”). It turned out that the gills of the giant clams and mussels at vents were also filled with symbiotic bacteria. Endosymbiosis is what allowed them to grow so big and so fast.
