Using boat, tags, nets, and submarines, marine biologists from 82 nations have been canvassing the oceans for the first Census of Marine Life, an ambitious effort to get a rough tally of all the creatures in the world’s oceans. The 10-year project is expected to conclude in 2010, and researchers say the broad survey will help them observe changes to marine ecosystems. Says co-senior scientist Ron O’Dor: “We are moving into this period of global warming, which is resulting in the acidification of the oceans, melting of the polar ice cap. We can use the first census as a benchmark to see what happens in the oceans over the next decade or more” [BBC News].
Although the project still has two years to go, researchers have already made a host of startling discoveries, many of which will be discussed this week at the World Conference on Marine Biodiversity in Valencia, Spain. In one study, researchers conducted a genetic analysis of deep sea octopuses from around the world, and determined that most descended from a common ancestor species that still lives near Antarctica. Researchers believe that octopuses started migrating to new ocean basins more than 30 million years ago when, as Antarctica cooled and a large icesheet grew, nature created a “thermohaline expressway,” a northbound flow of tasty frigid water with high salt and oxygen content. Isolated in new habitat conditions, many different species evolved; some octopuses, for example, losing their defensive ink sacs — pointless at perpetually dark depths [LiveScience].
Posts Tagged ‘sharks’
Curiosities of the Deep Revealed in First Census of Sea Life
Female Shark Gets Pregnant on Her Own, No Male Required
A female blacktip shark in a Virginia aquarium got pregnant despite the fact that no male blacktip sharks shared her tank in her eight years of residency, researchers say. This is the second documented case of asexual reproduction, or parthenogenesis, among sharks; the first example of a shark “virgin birth” occurred with a hammerhead shark in a Nebraska zoo. The new findings suggest that the previous event wasn’t a marine miracle. “This first case was no fluke,” Demian Chapman, a shark scientist and lead author of the second study, said in a statement. “It is quite possible that this is something female sharks of many species can do on occasion” [AP].
Now scientists are debating whether asexual reproduction is a backup method for female sharks that can’t find a mate, or whether the pregnancy was a developmental aberration that occurs from time to time. Chapman argues for the first camp: “The reason this has happened in captivity isn’t because there’s a change in their reproductive biology,” he explains. “It is more likely to happen if female sharks aren’t having enough dates,” he says. “These females did it because they were in captivity and ovulating” [Science News].
But others say that since the shark didn’t produce a normal litter of four to six pups, the pregnancy could have been an anomaly. “The fact that only one shark embryo was formed may suggest that this is more a case of an egg developmental aberration rather than a physiological response to the lack of a mate,” said [shark expert Robert] Hueter [National Geographic News].
Ancient “Big Tooth” Shark Had the Mightiest Bite in History
An extinct ancestor of the great white shark had a powerful bite that wouldn’t just put Jaws to shame, according to a new fossil analysis by Australian researchers. The colossal force of Carcharodon megalodon - also known as Big Tooth - made even Tyrannosaurus rex look puny [Telegraph].
In the study, to be published in an upcoming issue of the Journal of Zoology [subscription required], researchers took CT scans of both the skulls of great white sharks and those of the prehistoric megalodon, who swam the oceans about a million and a half years ago. They made computer models of the skulls, and then ran an analysis on the models that engineers use to determine how machinery holds up under stress.
Whale Sharks Dive-Bomb Through Deep Water Like Giant Raptors
For a big, lumbering creature, it sure is mysterious. Marine biologists don’t know much about the massive whale shark, which is considered the biggest fish on the planet. They don’t know how many there are or whether they are migratory, and its reproductive habits are obscure. There are even disputes about its size but it can grow reputedly to 60 feet long and weigh as much as 40 tonnes [Telegraph].
However, one thing researchers thought they knew was that whale sharks aren’t the speediest fish in the sea; in all previous sightings, the behemoths have always been cruising slowly just beneath the ocean’s surface. Now, after a couple of enterprising researchers clipped electronic tags to wild whale sharks near western Australia, biologists have realized that deep below the surface the creatures dive at great speeds, and that they use the same principles as a diving hawk. “It is like the way a bird dives – but, in this case, a bird as large as a bus,” said Professor Rory Wilson, who has tracked the movements of the threatened species [Daily Mail].
Embrace the Sharks, Before It’s Too Late
It’s not all about the cute fuzzy critters — we’ve got to save the toothy, menacing, bloodthirsty endangered species, too. That’s the message from a new study, which examined shark populations in the Mediterranean and found a lot to be alarmed about. Numbers of some species have fallen 97 percent over the last two hundred years due largely to overfishing, and researchers say that because sharks have been “much maligned,” no one seems to care.
[Lead author Francesco] Ferretti, a researcher at the Biology Department of Dalhousie University in Nova Scotia, said that Steven Spielberg’s 1975 film Jaws had given a misleading impression of sharks. “Spielberg has a lot to answer for,” he said. “In reality you have about as much chance of being eaten by a shark as you have of winning the lottery twice” [Times Online].
