A recently discovered "bone-eating" worm was found to have an even stranger quality: the large females contain "harems" of tiny males. In an even more recent twist, researchers found these characteristics were only present in some of these remarkable creatures.
The worm, called the Osedax, has now been pinned as an "evolutionary oddity" that is unlike anything that has ever been seen by science, the University of California, San Diego reported.
To make their findings the researchers looked at bone worms collected at a depth of 2,269 feet by an MBARI remotely operated vehicle. They observed a new type of Osedax species contained males tens of thousands of times larger than those that had been previously observed; these males were roughly the same size as the females.
"This discovery was very unexpected. It's the first known example of such a dramatic evolutionary reversal from dwarf males," said marine biologist Greg Rouse at Scripps Institution of Oceanography at UC San Diego.
"Evolutionary reversals to ancestral states are very rare in the animal kingdom," Robert Vrijenhoek of the Monterey Bay Aquarium Research Institute (MBARI) continued. "This case is exceptional because the genes for producing full-sized adult males should have deteriorated over time due to disuse. But apparently the genes are still there."
The researchers found the males of this new species consumed bone on their own, which is a behavior not observed in their smaller relatives. The mating process observed in the new species was also found to be very different from the previously discovered organisms. The smaller males are permanently attached to their female hosts and do not need mobility to mate, but that couldn't be the case in the species with larger males.
"The evolutionary solution (the new species) found was to actually make the male's body very extendable so he can reach far out to find females to mate with -- he can extend his body 10 times its contracted state," Rouse said.
These findings suggest the worm's body evolved as a mating tool. The researchers believe less competition for space on animal bones allowed for this interesting evolution.
"This worm was weird enough as it was, and now it's even weirder," Rouse concluded. "This shows us that there continue to be mysteries in the sea and there is still so much more to discover, especially since we only found these creatures 12 years ago."
The findings were published Dec. 11 in the journal Current Biology.
