[转贴]：We may have lost one of our national symbols

The BBC television network has reported that Panama's golden frogs, a species of harlequin frogs that's one of our unofficial national symbols, are now extinct in the wild. This, according to scientists, has been the fate of about two-thirds of the harlequin frog species.

The killer is chitrid disease, an infection by the Batrachochytrium dendrobatidis fungus, which generally attaches itself to the frogs when they are in their tadpole stage of development and ultimately kills them as adults. Recent studies have shown that global warming is linked to the mass extinction of tropical frogs, as some sort of trigger mechanism for the fungal infections.

The presence of Batrachochytrium dendrobatidis in the frogs' natural environments has been known for a long time, since well before it began affecting frogs. The precise mechanism of how it has in recent years become a deadly pathogen for frogs is still something of a mystery. It may be due to a mutation in the fungus, a weakening of the frogs' natural resistance to infection, an environmental shift that has reduced natural forces that limit the fungus or some other mechanism. A recent paper published in Science magazine shows that the infection's spread has closely tracked climate changes that make days cooler (from more cloud cover) and nights warmer in the habitats along tropical streams where the frogs live.

The frog extinction is not just of interest to nature lovers, and is not just because frogs may be an "indicator species" that warns of changes that will soon be felt by others. The investigation of the mechanisms of the fungal infection epidemic may lead scientists to better understand the nature of the threat of "emerging diseases" that can ravage humanity, either directly or as agricultural blights that in turn cause hunger.

A preservation effort has kept a number of the Panamanian golden frogs alive in captivity, so there is a possibility that at some future date they may be reintroduced into natural settings. 

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