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Science and technology
科學技術
Arachnology
節肢動物學
Having a mate for dinner
情人為食
Male spiders make the supreme sacrifice for their children
雄蛛對后代的無私奉獻
AMONG spiders, the female of the species really is more deadly than the male.
蜘蛛家族中,雌蛛致命性比雄蛛高得多。交配后將配偶狼吞虎咽地吃掉，雌蛛因此聲名在外。
Lady arachnids have a well-deserved reputation for polishing off their suitors, post copula, in a manner that Hannibal Lecter might have admired.
它們的這一行為或許在一定程度上贏得了漢尼拔萊克特的敬仰，
But it has never been clear why this happens.
然而其原因一直不為人所知。
Some biologists believe it is simply a mixture of female hunger and the availability of a meal that is in no position to run away.
一些生物學家認為這僅僅是因為雌蛛餓了，而盤中餐又無力逃脫。
Others suspect that the male is actually sacrificing his life for the good of his genes.
一些生物學家認為雄蛛是為他的基因而犧牲的。
In other words, his becoming a meal for his paramour somehow helps the offspring of their union.
換句話說，他成為情人的腹中食某種程度上有助于他們共同的后代。
Peng Yu, of Hubei University in China, and his colleagues, decided to try to settle the question.
中國湖北大學的彭宇及其同事決定嘗試解開這一謎題。
The results of their investigation are published this week in Behavioral Ecology and Sociobiology.
他們的條查結果刊登在《行為生態學與社會生物學》。
Dr Peng and his team collected almost 400 young wolf spiders, of both sexes, from local fields.
彭博士和他的小組在當地收集了幾乎400只狼蛛，
They then raised the animals separately until they were sexually mature.
再雌雄分開飼養，直到它們性成熟。
Then, one at a time, they introduced the females to a male and watched until one of three things happened:
然后他們每次一只，將雌蛛與雄蛛配對，直到出現以下三者之一的情況發生：
the male got eaten; the male mated with the female and successfully avoided being eaten; or the male survived for half an hour, but did not mate with the female within that time.
雄蛛被吃；雄蛛與雌蛛交配后幸免于難；或者雄蛛存活了半小時，而期間未與雌蛛交配。有時，他們將未交配的雌雄蛛配對；
Sometimes the researchers paired virgin males with virgin females; sometimes they paired virgin males with females that had recently bred.
有時他們將未交配的雄蛛與剛繁殖過的雌蛛配對。
And in one crucial set of tests they paired virgin males with virgin females that had been taken off their regular diet of fruit flies a fortnight beforehand, and were thus presumed to be feeling more than a little peckish.
在一項關鍵性實驗中，他們將未交配的雄蛛與停飼果蠅兩周的雌蛛配對—此時假設雌蛛處于極度饑餓狀態。
After doing all this, the team chose 16 females that had mated and then eaten their partners, and ten that had mated but not done so, and followed their reproductive success.
配對后，實驗小組挑選了16只交配后吃掉配偶的雌蛛，10只交配后未吃掉配偶的雌蛛，觀察其繁殖成功的過程。
When these females laid their egg sacs, the researchers picked ten sacs at random from each group and monitored those until the eggs hatched.
當這些雌蛛產下卵袋時，研究者從每組隨機挑選了10個卵袋觀察，直到卵孵化。
At that point they selected 20 spiderlings from each group for further study.
這時，他們從每組挑選10只幼蛛用于后續研究。
Their first pertinent observation was that, while female wolf spiders did indeed sometimes eat males before breeding with them, that happened only 10% of the time, and did not seem to be more frequent if the female had been starved.
他們第一個客觀觀察結果是，雌狼蛛有時確實會在交配前吃掉雄狼蛛，這種概率是10%，并且似乎不比雌蛛挨餓后比率高。
Their second observation was that if a male was deemed suitable to mate with, he was never eaten in copula—even though copulation could last as long as an hour and a half.
第二個觀察結果是，如果雄蛛被認為適合交配，它們絕不會在交配中被吃—即使交配過程可能長達一個半小時。
Their third was that, 28% of the time, a male that had mated was indeed eaten afterwards.
他們第三個觀察結果是，有28%的幾率雄蛛會在交配后被吃。
Successful suitors, then, succumbed more often than unsuccessful ones.
如此可得出，交配成功的雄蛛被吃的比未成功的多。
The crucial finding, however—which makes sense of all the others—was the success of the spiderlings.
然而，幼蛛成活率是關鍵的發現—這使得其他發現都有了意義。
Young born of females that had eaten their partners had a 48% chance of making it through their first month of life.
吃掉配偶的雌蛛其后代48%可以活過一個月，
Those born of females who had let their partners live, had only a 12% chance of surviving that long.
而放生配偶的雌蛛的后代存活相同時間的只有12%。
That is a staggering difference—and certainly, in evolutionary terms, enough to drive self-sacrificial behaviour by males,
這個差距是巨大的—當然，按照進化論原則，足以使雄蛛采取自我犧牲行為。
since a male would have to mate successfully another three times to match the benefit he gains by this one suicidal act.
因此，為獲得這一次自殺行為帶來的好處，它之前必須成功交配三次。
The reason a male is almost three times as likely to be eaten if he has mated with the female in question than if he has not is thus probably that he wants to be eaten, for the good of his posterity.
討論中，如果與雌蛛交配成功，雄蛛被吃的概率幾乎是未交配成功的雄蛛的三倍，其原因可能是為后代著想，它希望被吃。
Just what it is that a male meal gives, via the female's digestive system, to the hatchling spiders, remains to be determined.
通過雌蛛的消化系統，雄蛛給予孵化蜘蛛的是什么？這還有待探索。
Perhaps spider bodies contain some crucial nutrients which are scarcer in other forms of prey.
也許蜘蛛體內含有其他獵物所缺乏的重要的營養成分。
Whatever the details, though, the general answer to the biologists' question is now clear.
不管具體如何，生物學家們的問題有了大致的答案。
In the case of spiders, fathers really do lay down their lives for their children.
對蜘蛛來說，父親們真真是為孩子放棄了他們的生命。
