Monday, December 4, 2006
Ancient Fish Had Fiercest Bite
Sharks were not always the top predators in the ocean.
Dunkleosteus terrelli, an armored fish that grew up to 33 feet long and lived 400 million years ago, had jaws strong enough to bite a shark in two, according to research published last week in the journal Biology Letters.
Scientists from the University of Chicago and the Field Museum created a biomechanical model of the skull of what they call the "Darth Vader of fishes" from a fossil that is on permanent exhibition at the museum.
The creature, one of various kinds of armored fishes known as placoderms that ruled aquatic ecosystems from 415 million to 360 million years ago, had the strongest bite ever for a fish, delivering a force of 8,000 pounds per square inch at the tip of its fangs. Its bite was strong enough to rival that of a Tyrannosaurus rex, and it allowed Dunkleosteus terrelli to snack on sharks and other tough-hided fish of the era. The model also demonstrates that the fish could open its jaws quickly, within a 50th of a second, creating suction that helped pull in its prey.
The fast and powerful jaws, made possible by four rotational joints working together, "made this fish into one of the true apex predators seen in the vertebrate fossil record," said Mark Westneat, curator of fishes at the museum and co-author of the study.
-- Christopher Lee
Climate May Threaten Penguins
The animated movie "Happy Feet" suggests that overfishing is imperiling penguins' survival, but a petition from an environmental advocacy group suggests that climate change poses a greater threat to the photogenic creatures.
In a petition filed last week, the Center for Biological Diversity asked the U.S. government to add 12 penguin species to the federal Endangered Species Act.
The group said unusually warm ocean temperatures have diminished the food available for penguins: The size of the Emperor penguin colony at Pointe Geologie, Antarctica, featured in the Oscar-winning documentary "March of the Penguins," dropped by half between 1952 and 2000, researchers found.
"These penguin species will march right into extinction unless greenhouse gas pollution is controlled," said the center's Kassie Siegel. "It is not too late to save them, but we must seize the available solutions to global warming immediately."
Interior Department spokesman Hugh Vickery said the U.S. Fish and Wildlife Service will decide whether the petition merits a full review.
"Obviously, not all petitions are created equal," Vickery said. "The key question is whether the petition presents sufficient scientific evidence."
The species listed in the petition are Emperors, Southern Rockhopper, Northern Rockhopper, Fiordland Crested, Snares Crested, Erect-crested, Macaroni, Royal, White-flippered, Yellow-eyed, African and Humboldt.
Brendan Cummings, who directs the Center for Biological Diversity's oceans program, said overfishing has affected some species, such as the Humboldt and African penguins. "It's essentially food competition," he said.
-- Juliet Eilperin
Sea Grass Loss Said to Be Crisis
Sea grasses, which grow in underwater meadows along many coastlines, are essential to the well-being of many marine species and to the health of coastal ecosystems. But they are sensitive to pollution and sudden explosions of underwater nutrients, and are endangered in many places.
"Seagrasses are the coal-mine canaries of coastal ecosystems," according to William Dennison of the University of Maryland Center for Environmental Science, co-author of a report in this month's issue of the journal BioScience. "The fate of seagrasses can provide resource managers advance signs of deteriorating ecological conditions caused by poor water quality and pollution."
The researchers found that the undersea meadows, which rival rice paddies in their rate of photosynthesis and are important nurseries and habitat for many fish and prawns, are on the decline from the eastern Mediterranean to Japan to the Chesapeake Bay; the decline parallels drops in the health of coral reefs, salt marshes and coastal mangrove forests. The authors said human activity has the most direct and immediate impact on sea grasses.
Sea grasses, which flower underwater, evolved from land plants during the time of the dinosaurs and have adapted to a fully submerged existence. There are only 55 species, compared with 5,000 to 6,000 species of seaweed, which is a form of algae.
The authors wrote that the loss of sea grasses is a "crisis" that is being ignored compared with the attention paid to coral reefs and salt marshes.
-- Marc Kaufman