2015/01/28 - 救救北極熊，，老二骨質疏鬆該掛哪一科門診?
今日知識: 原來北極熊的老二有骨頭 and 只有那裏骨質疏鬆也太怪了吧! (想笑怕失禮)
Polar bears just can't seem to catch a break. It's no secret that populations of these Arctic animals are in decline, expected to go extinct by 2100, as they remain threatened by melting ice, dangerous conditions and fewer hunting opportunities. But now, new research shows that polar bear penis bones are weakening due to chemical pollution.
This puts them at risk of literally breaking their penises, which could have disastrous consequences for mating and the survival of this endangered species.
The findings are published in the journal Environmental Research.
Despite commonly known slang terms, the human penis does not contain any bones. However, polar bears are obviously different, and possess a penile bone known as a baculum (though its exact function remains unknown). Some believe the baculum supports the genitals or stimulates females during sex.
It was already known that the sex organs of polar bears were shrinking over time due to high levels of pollutants called organohalogens. But now a team of scientists at Aarhus University, Denmark, has found that a certain type of organohalogen called polychlorinated biphenyls, or PCBs, is associated with a less dense penile bone.
"These chemicals enter the atmosphere at lower latitudes where they were used, and are then deposited down from the cold polar air, so Arctic animals are more highly exposed than animals in more temperate or equatorial regions," University of Florida researcher Margaret James, who was not involved in the study, told New Scientist.
PCBs and Penises
Use of PCBs began in the early 20th century, involved in the production of different kinds of plastics and rubbers. And although they were banned by the United Nations in 2001 (it turns out they can cause cancer), they are slow to break down, and therefore difficult to remove from the environment. The Washington Post notes that they get stuck to sediments and are carried through waterways, building up in concentration (and toxicity) the higher up you go in the food chain.
This is bad news for polar bears, the world's largest land carnivores. Together with a team from Canada, led author Christian Sonne and his colleagues examined baculum specimens from 279 polar bears that were born in northeast Greenland and Canada between 1990 and 2000.
"It's the kind of bone that's taken by local trophy hunters and subsistence hunters. It's an actual sign that you have hunted and shot a bear," Sonne explained. (Scroll to read on...)
They used X-rays to study the density of calcium in the bones and then compared their findings with regional pollutant data. The authors found a link between high levels of PCBs and low baculum density. While they can't conclusively blame PCBs, the study does suggest that these chemicals are involved.
And despite the mystery of the baculum's purpose, Sonne does add that it is likely a weaker baculum creates problems during mating.
"If it breaks, you probably won't have a bear which can copulate," he told New Scientist.
What's more, it seems that climate change and this pollution problem are reinforcing one another, putting polar bears in a no win situation.
"Skinny bears have higher levels of circulating pollutants, so the concern is that a bear that is nutritionally stressed may become more vulnerable to the effects of pollution at the same time," explained researcher Andrew Derocher at the University of Alberta in Canada.
PCBs just add another problem to the equation, creating some serious problems for one of the Arctic's most iconic species. If climate change continues at its current rate, this cold-weather species has no hope. No thanks to humans, polar bears have already taken matters into their own hands (or paws), shifting their distribution patterns towards icier areas further north to combat warming temperatures and dramatic losses in sea ice.
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