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【科普】袋獾通过交配来与癌症战斗
Tasmanian devils have for some years been plagued with a mysterious and lethal cancer. Now, the dog-sized mammals are fighting back: They are breeding at younger ages.
Devils are furry marsupials, mammals that have no true placentas — females usually have pouches to carry and suckle newborns. They reside only on the island of Tasmania, though fossil evidence suggests that long ago Tasmanian devils (Sarcophilus harrisii) were spread across the Australian mainland. Devils are known for their offensive odor, disturbing screeches and viciousness when they eat, mostly carrion.
Hunters considered the devils pests to livestock and took a toll on the population in the mid-1800s. Now the devil facial tumor disease is killing the animals within a year of reaching maturity. The infectious cancer is spread directly through biting. The tumors mainly affect adults at least 2 years old, causing death within months.
Menna Jones of the University of Tasmania and colleagues examined data collected before and after the arrival of the disease from five Tasmanian devil populations on the island.
A much higher proportion of older adults, over the age of 3, were present in the populations before the disease appeared.
After disease emergence, precocial breeding by 1-year-old females increased dramatically at four sites, increasing from between zero and 12.5 percent beforehand to between 13 percent and 83 percent after. The range in percentages reflects the different findings at each of the sites on the island.
Reduced population density and reduced competition for food could be behind any growth spurts that would allow juveniles to reproduce before their time, the researchers suggest.
Symptoms of the disease, including cancerous lesions around the mouth, face and neck, were first reported in 1996 at one spot on Tasmania. By 2007, the disease had spread over more than half of the devils' home range there. Some populations have lost up to 89 percent of their members as a result of the facial tumors.
The newly discovered precocial breeding could help to keep the species from vanishing, the researchers speculate.
The study, reported this week in the journal Proceedings of the National Academy of Sciences, was funded by the Australian Research Council, the Australian National University Faculties Research Grants Scheme, and the Tasmanian Government Save the Tasmanian Devil Program.
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screen.width-333)this.width=screen.width-333" width=163 height=110 title="Click to view full 080714-tasmanian-devil-01.jpg (163 X 110)" border=0 align=absmiddle> Fatal tumors force early mating in Tasmanian devils
致命的癌症促使袋獾提前交配
Tasmanian devils have for some years been plagued with a mysterious and lethal cancer. Now, the dog-sized mammals are fighting back: They are breeding at younger ages.
多年来，袋獾一直被一种神秘而致命的癌症所折磨。如今，这种大小似狗的哺乳动物寻找到了对策――早熟繁殖。
Devils are furry marsupials, mammals that have no true placentas — females usually have pouches to carry and suckle newborns. They reside only on the island of Tasmania, though fossil evidence suggests that long ago Tasmanian devils (Sarcophilus harrisii) were spread across the Australian mainland. Devils are known for their offensive odor, disturbing screeches and viciousness when they eat, mostly carrion.
袋獾是浑身覆盖毛皮但没有真正胎盘的有袋目哺乳动物－母亲用袋子携带并哺乳幼儿。尽管化石证明袋獾在很久之前遍布澳洲大陆，但目前他们只居住在塔斯马尼亚岛上。袋獾因其恶臭、烦人的尖叫和吃腐肉时的邪恶而闻名。
Hunters considered the devils pests to livestock and took a toll on the population in the mid-1800s. Now the devil facial tumor disease is killing the animals within a year of reaching maturity. The infectious cancer is spread directly through biting. The tumors mainly affect adults at least 2 years old, causing death within months.
在19世纪中期，猎人认为袋獾对家畜有害，因此对其数量加以控制。如今，在一年内达到成熟的袋獾会因得面部肿瘤而死。这是一种传染性肿瘤，可以直接通过撕咬得到传播。这种肿瘤影响的主要是至少2岁的成年袋獾，导致其在数月内身亡。
Menna Jones of the University of Tasmania and colleagues examined data collected before and after the arrival of the disease from five Tasmanian devil populations on the island.
塔斯马尼亚岛大学的Menna Jones及其同事对这种肿瘤发生前后的岛上的5个袋獾种群的数据进行了分析。
A much higher proportion of older adults, over the age of 3, were present in the populations before the disease appeared.
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作者:admin@医学,生命科学 2011-07-29 17:11
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