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PNAS:真菌可能是火蝾螈衰退的关键

来源:EurekAlert!中文 2013-09-03 09:06

科研人员分离出了一种此前未知的真菌,它被认为是驱动着欧洲西北部的火蝾螈种群走向几乎灭绝的原因。真菌疾病壶菌病是由水生真菌蛙壶菌(Batrachochytrium dendrobatidis,Bd)引起的,它已经在20世纪90年代以来导致了全球200多种两栖动物的衰退。但是并非所有两栖动物的死亡都与蛙壶菌有关。An Martel及其同事寻找了困扰着当地火蝾螈(Salamandra salamandra)种群的这种神秘病原体,并且发现了第二种蛙壶菌致病病原体:一种壶菌真菌,作者将其命名为Batrachochytrium salamandrivorans sp. nov。这组作者报告说,从这种全球衰退当中死亡的火蝾螈的皮肤损伤中分离出的这些真菌看上去为寄生在脊椎动物身上做好了准备。这些真菌比蛙壶菌喜欢更凉爽的气候,在50到59华氏度之间生长得最好,并且无法在华氏77度以上的温度下生存。这项研究发现,实验性地让产婆蟾感染了B. salamandrivorans,结果表明它能抵抗这种迅速杀死其他两栖动物的侵蚀性的皮肤疾病。这组作者说,这些发现提示B. salamandrivorans与其亲缘关系相近的蛙壶菌相比,它可能在两栖动物世界中占据了一个不同的生态位。(生物谷 Bioon.com)

生物谷推荐的英文报道

Fire salamanders, recognisable by their distinctive yellow and black skin patterns, have been found dead in the country's forests since 2010. The population has fallen to around 10 individuals, less than four per cent of its original level, but what has been killing them has been a mystery until now.

Scientists from Ghent University, Imperial College London, Vrije Universiteit Brussel and the Dutch conservation group Ravon have isolated a new species of fungus from the dead animals and found that it can rapidly kill fire salamanders. They have named the fungus Batrachochytrium salamandrivorans, the second part meaning "salamander-eating," and report their findings today in the Proceedings of the National Academy of Sciences.

Fungi are increasingly recognised as important threats to biodiversity. A species related to the new fungus, Batrachochytrium dendrobatidis (Bd), has plagued amphibian populations across the globe and is thought to have wiped out more than 200 species worldwide. It causes the disease chytridiomycosis, which the International Union for the Conservation of Nature has called the single most devastating infectious disease in vertebrate animals.

The study's lead author, Professor An Martel from the University of Ghent, said: "In several regions, including northern Europe, amphibians appeared to be able to co-exist with Bd. It is therefore extremely worrying that a new fungus has emerged that causes mass mortalities in regions where amphibian populations were previously healthy."

Co-author Professor Matthew Fisher, from Imperial College London, said: "It is a complete mystery why we are seeing this outbreak now, and one explanation is that the new salamander-killing fungus has invaded the Netherlands from elsewhere in the world. We need to know if this is the case, why it is so virulent, and what its impact on amphibian communities will be on a local and global scale. Our experience with Bd has shown that fungal diseases can spread between amphibian populations across the world very quickly. We need to act urgently to determine what populations are in danger and how best to protect them."

The fungus can be passed between salamanders by direct contact, and possibly by indirect contact although this hasn't been proven. It invades the animal's skin, eventually destroying it completely. In tests, the fungus was not able to infect midwife toads, which have been threatened by chytridiomycosis, but whether other species might be vulnerable is unknown.
The scientists have brought surviving salamanders into captivity to protect the remaining population in the Netherlands. To aid further studies, they have also developed a diagnostic tool that enables the new fungus to be quickly identified. They tested 100 salamanders from Belgium, where the population has remained healthy, but so far there is no sign that the fungus has spread beyond the Netherlands.

The research was funded by the Royal Zoological Society of Antwerp, the European Research Council and Biodiversa.

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