for National Geographic News
Every fall, scores of leviathans fill Monterey Bay in California, an army of parasite-ridden ocean dwellers with truncated bodies that make them look like swimming heads.
But these are no bloodthirsty sea monsters. They're Mola mola, or giant ocean sunfish, gentle creatures named for their habit of lying at the ocean surface, appearing to sunbathe. The largest bony fish in the world, the molas can grow to be over 10 feet (3 meters) long and weigh up to 5,000 pounds (2,250 kilograms).
Yet despite their appearance, little is known about them.
Tierney Thys is changing all that. For the past three years, the Monterey-based marine biologist and her colleagues have plunged into the world's oceans, using satellite tagging and DNA analysis to uncover the secrets of one of the most peculiar inhabitants of the sea.
Her study, which is partly funded by the National Geographic Society Committee for Research and Exploration, is revealing new insights into how the molas live, how they reach such gargantuan proportions, and how they tie into the vast web of open ocean life.
"Contrary to popular belief that the mola is simply a lazy lollygagging sunbather, it is in fact quite an industrious creature, plumbing the cold dark depths of the ocean repeatedly over the course of a day," said Thys.
"In today's ocean, highly impacted by human actions through climate change, overfishing, and pollution, some experts predict that only low energy forms like jellyfish will prosper," added Thys. "The mola, which subsists primarily on a jellyfish diet, could end up being the fish of the future."
Thys, a California native, became fascinated with the mola after seeing a picture of it on her advisor's wall at Duke University in Durham, North Carolina, where she earned a doctorate degree in zoology, specializing in biomechanics, in 1998.
"I thought, 'That's got to be the most unlikely fish in the sea,'" recalled Thys, whose dissertation investigated the mechanics of swimming muscles in fish. "What in the world is that animal's story?"
After swimming with the molas in the wild, she was hooked. "They may look goofy, but they are spectacular underwater, incredibly graceful, like a slow flapping bird gliding on the ocean currents," Thys said.
Silver-colored, the molas have a rounded hind end and gritty sandpapery skin that is covered with copious amounts of mucus. They're infamous for their impressive parasite load. Some 40 different types of parasites have been recorded on these fish. A female may carry more than 300 million eggs in her single ovary.
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