English Eye
Study: Parasitic fly could explain bee die-off
Published : Jan 5, 2012 - 10:57
Updated : Feb 3, 2012 - 14:17

FRESNO, California (AP) _ Northern California scientists say they have found a possible explanation for the honey bee die-off: A parasitic fly that hijacks the bees' bodies and causes them to abandon hives.

The symptoms mirror colony collapse disorder, in which all the adult honey bees in a colony suddenly disappear. The disorder continues to decimate hives in the U.S. and overseas.

The disease is of great concern, because bees pollinate about a third of the United States' food supply. Its presence is especially alarming in California, America's top producer of fruits and vegetables, where bees play an essential role in the $2 billion almond industry and other crops.

The latest study, published Tuesday in the science journal PLoS ONE, points to the parasitic fly as the new threat to honey bees. It's another step in ongoing research to find the cause of the disease.

Researchers haven't been able to pin down an exact cause of colony collapse or find a way to prevent it. Research so far points to a combination of factors including pesticide contamination, a lack of blooms _ and hence nutrition _ and mites, fungi, viruses and parasites.

Interaction among the parasite and multiple pathogens could be one possible factor in colony collapse, according to the latest study by researchers at San Francisco State University. It says the phorid fly, or apocephalus borealis, was found in bees from three-quarters of the 31 hives surveyed in the San Francisco Bay area.

Scientists say the fly deposits its eggs into the bee's abdomen, causing the insect to walk around in circles with no apparent sense of direction. The bee exhibits zombie-like behavior, said lead investigator John Hafernik. The infected bee leaves the hive at night and dies shortly thereafter.

The combination of a parasite, pathogens and other stressors could cause die-off, Hafernik said. The parasitic fly serves as a reservoir that harbors pathogens _ honey bees from parasite-infected hives tested positive for deformed wing virus and other pathogens, the study found.

``We don't fully understand the web of interactions,'' Hafernik said. ``The parasite could be another stressor, enough to push the bee over tipping point. Or it could play a primary role in causing the disease.''

Hafernik stumbled onto the parasitic fly by accident. Three years ago, the biology professor looked for something to feed a praying mantis. He found some bees outside his classroom, placed them in a vial and forgot about them. When he looked at the vial a week later, he found dead bees surrounded by small fly pupae. A parasitic fly was feeding on the bees and had killed them, he said.

The fly is a known parasite in bumble bees. Scientists used DNA barcoding to confirm the parasite in the honey bees and bumble bees was the same species.

The fly might have recently expanded its host presence from bumble bees to honey bees, Hafernik said, making it an emerging threat to agricultural pollinators. The fact that honey bees live in large colonies placed in close proximity to one another and beekeepers frequently move the hives throughout the country could lead to an explosion of the fly population, he said.

The fly, which is found all over North America, could also become a threat to native bees.

Hafernik plans to expand his research to other parts of the country and to study the parasite's impact on agriculture in California's Central Valley.

Since it was recognized in 2006, colony collapse has destroyed colonies at a rate of about 30 percent per year, according to the U.S. Department of Agriculture. Before that, losses were about 15 percent per year from a variety of pests and diseases.



사라지는 꿀벌들..기생 파리의 습격때문

전세계적으로 꿀벌 수가 급격히 줄어드는 이유가 기생파리의 습격때문이라는 연구결과가 발표되었다.

AP등 외신들에 따르면 기생하는 파리가 꿀벌의 정신을 혼미시켜 몸뚱이를 공중납치해 그들의 삶의 터진인 꿀벌통을 떠나게한후 죽게만든다는것이다.

최근 세계 곳곳에서 꿀벌통에서 꿀벌들이 모두 사라져버리는 이른바 '군생 붕괴' 현상이 일어나 양봉업계 종사자들과 과학계의 우려를 샀다.

양봉업만이 문제는 아니다. 미국의 총 식량 생산물의 3분의 1를 꿀벌이 꽃가루받이 해줘서 열매 등을 맺게 하는등 꿀벌은 인간의 작물산업에서 필수적이다.

과학자들은 그간 사라지는 꿀벌들에 대해 살충제오염이거나 진드기 혹은 바이러스 기생충 탓이라고 여러 이론을 내놨다.

하지만 샌프란시스코 주립 대학교 연구팀은 기생 파리가 이 꿀벌의 서식지 붕괴를 일으킨다고 새로운 연구결과를 발표했다.

이 기생 파리는 꿀벌의 배에 알을 까는데, 꿀벌은 어느 날 방향 감각을 상실한 채 빙빙 걷게 된다고 한다.

벌은 이른바 좀비상태가 되어 밤중에 살던 벌통을 떠나 얼마 있다 죽음을 맞이한게된다고.

그러나 정확한 이 벌통 붕괴현상의 메카니즘은 아직 이해되지 않고 있다고 연구팀이 밝혔다.

지난 2006년 처음 발견된 벌통 붕괴현상이 관찰된 이후 기존 꿀벌통은 해마다 30% 가량 손실돼 왔다.

미 농무성은 이 병통이 있기 전에는 이미 해충과 병 등으로 약 15% 정도 사라졌다고 전했다.