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voa有聲雙語新聞

為什么有些人招蚊子 Why do some people recruit mosquitoes

Some people can sit outside all summer long and not suffer from mosquito bites.Others turn into an itchy mess despite bathing in DEET and never leaving the purple glow of the bug zapper.

有些人可以整個夏天坐在戶外乘涼卻不被蚊子叮咬，而另有一些人即便用含驅(qū)蚊胺的沐浴露洗浴、隨身帶著滅蚊燈，卻仍遭蚊子叮咬而奇癢難耐。

It's mostly about the invisible chemical landscape of the air around us.Mosquitoes take advantage of this landscape by using specialized behaviors and sensory organs to find victims by following the subtle chemical traces their bodies leave behind.

這主要是因為我們身體周圍空氣中肉眼看不見的化學(xué)成分。通過特殊習(xí)性和感覺器官，蚊子利用這種化學(xué)環(huán)境，跟蹤人體留下的細微化學(xué)痕跡找到叮咬對象。

In particular,mosquitoes rely on carbon dioxide to find their hosts.When we exhale,the carbon dioxide from our lungs doesn't immediately blend with the air.It temporarily stays in plumes that mosquitoes follow like breadcrumbs.

具體來說，蚊子能夠靠人體釋放的二氧化碳找到它們叮咬的對象。當(dāng)我們呼氣時，從肺里呼出的二氧化碳并非立即與空氣混合，而是暫時形成類似于面包粉的團塊狀氣流，而蚊子會跟蹤這種氣流。

"Mosquitoes start orienting themselves to those pulses of carbon dioxide and keep flying upwind as they sense higher concentrations than the normal ambient air contains,"said Joop van Loon,an entomologist at Wageningen University in the Netherlands.Using carbon dioxide,mosquitoes can lock onto targets from up to 164 feet(50 meters)away.

荷蘭瓦赫寧恩大學(xué)的昆蟲學(xué)家約普·范隆說：“蚊子開始自我定位，跟蹤那些二氧化碳氣流，并在它們感覺到二氧化碳濃度比正常環(huán)境空氣的濃度高時保持逆流飛行。”利用二氧化碳，蚊子可以鎖定164英尺(約合50米)以外的目標(biāo)。

Things start getting personal when mosquitoes get about 3 feet(1 meter)away from a group of potential targets.In close quarters,mosquitoes take into account a lot of factors that vary from person to person,including skin temperature,the presence of water vapor and color.

當(dāng)蚊子飛到離一群潛在目標(biāo)大約3英尺遠時，就開始區(qū)分每個人的不同情況。在近距離時，蚊子考慮很多因人而異的因素，包括皮膚溫度、水汽的存在和顏色。

Scientists think the most important variable mosquitoes rely on when choosing one person over another are the chemical compounds produced by the colonies of microbes that live on our skin.

科學(xué)家們認為，蚊子選擇某個特定的人作為叮咬目標(biāo)依據(jù)的一個最重要因素是，皮膚上微生物菌落產(chǎn)生的化學(xué)成分。

"Bacteria convert the secretions of our sweat glands into volatile compounds that are taken through the air to the olfactory system on the head of the mosquitoes,"Van Loon told Live Science.

范隆告訴美國趣味科學(xué)網(wǎng)站說：“細菌把人類汗腺的分泌物變成揮發(fā)性混合物，通過空氣進入位于蚊子頭部的嗅覺系統(tǒng)。”

These chemical bouquets are complex,including upward of 300 different compounds,and they vary from person to person based on genetic variation and environment.

這些混合物的化學(xué)氣味很復(fù)雜，含有300多種成分，而且因為基因差異和環(huán)境不同，因人而異。

"If you compare a father and daughter in the same household,there can be differences in the ratios of the chemicals the microbes are making,"said Jeff Riffell,an associate professor of biology at the University of Washington who has studied mosquito attraction.

美國華盛頓大學(xué)研究蚊子吸引力的生物學(xué)副教授杰夫·里費爾說：“即使拿一個家庭里的父親與女兒做比對，微生物產(chǎn)生的化學(xué)物質(zhì)比例可能也有差異。”

For instance,men with a greater diversity of skin microbes tended to get fewer mosquito bites than men with less diverse skin microbes did,a 2011 study in the journal PLOS ONE found.Moreover,men with less diverse microbes tended to have the following bacteria on their bodies:Leptotrichia,Delftia,Actinobacteria Gp3 and Staphylococcus,the researchers said.

譬如，2011年發(fā)表在美國《公共科學(xué)圖書館·綜合》雜志上的一篇研究報告發(fā)現(xiàn)，皮膚微生物多樣性較高的男性往往比皮膚微生物多樣性較低的男性少招蚊子叮咬。而且研究人員稱，皮膚微生物多樣性較低的男性，他們皮膚上往往有下列幾種細菌：纖毛菌、代爾夫特菌、放線菌Gp3和葡萄球菌。

In contrast,men with a diverse array of microbes tended to have the bacteria Pseudomonas and Variovorax on their skin,that study found.

研究發(fā)現(xiàn)，相比之下，有多種多樣微生物的男性，在他們的皮膚上往往有假單胞菌和貪嗜菌。

Subtle differences in the composition of these chemical bouquets can account for big differences in how many bites a person gets.The composition of those microbial colonies can also vary over time in the same individual,particularly if that person is sick,Riffell said.

這些化學(xué)氣味成分的細微差異在一個人遭蚊子叮咬時會產(chǎn)生巨大差異。里費爾說，同一個人，這些微生物菌落的組成也可能隨時間變化而不同，尤其是在此人生病的時候。

We don't have much control over the microbiomes on our skin,but Riffell did offer some advice based on his research.

我們對皮膚上的微生物沒有太多控制權(quán)，但里費爾根據(jù)他的研究結(jié)果給出了一些建議。

"Mosquitoes love the color black,"so consider wearing something lighter at your next cookout,he said.

他說，“蚊子喜歡黑色”，因此下次露天燒烤時，可以考慮穿淺色衣物。

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