情人成了盤中餐

AMONG spiders, the female of the species really is more deadly than the male. Lady arachnids have a well-deserved reputation for polishing off their suitors, post copula, in a manner that Hannibal Lecter might have admired. But it has never been clear why this happens. 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. Others suspect that the male is actually sacrificing his life for the good of his genes. In other words, his becoming a meal for his paramour somehow helps the offspring of their union.

蜘蛛家族中，雌性蜘蛛要比雄性蜘蛛致命的多。雌性蛛形綱類蜘蛛擁有當之無愧的聲望，因為當她們在和雄性蜘蛛交配完之後，便立即吃掉了該雄性蜘蛛。而漢尼拔對這種舉止感到吃驚。 但是對於雌性蜘蛛這種驚異的的舉止，生物學家迄今為止還沒有找到合理的解釋。一些生物學家認為，這只是雌性蜘蛛當時的飢餓以及食物的易於得到促使的。因為在蜘蛛交配扥情況下，雄性蜘蛛無處可逃。還有一些生物學家認為，雄性蜘蛛為了使其後代擁有優良的基因而犧牲了他們自己。總之，在某種程度上，由於雄性蜘蛛成為他們情人的盤中餐，他們的後代變得更為團結。

Peng Yu, of Hubei University in China, and his colleagues, decided to try to settle the question. The results of their investigation are published this week in Behavioral Ecology and Sociobiology.

在中國，湖北大學的彭雨博士和他的同事們嘗試去解開這個謎團。他們的研究結果刊登在本周的行為生態學、生物學的期刊上。

Dr Peng and his team collected almost 400 young wolf spiders, of both sexes, from local fields. They then raised the animals separately (in order to avoid premature cannibalistic accidents) until they were sexually mature.

彭博士和他的研究團隊從田裡抓了近400隻年輕雌雄狼蛛。然後彭博士他們將這些狼蛛分隔開來（避免成熟前同類相食的情況發生），直到這些狼蛛長成成年。

Then, one at a time, they introduced the females to a male and watched until one of three things happened: 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. Sometimes the researchers paired virgin males with virgin females; sometimes they paired virgin males with females that had recently bred. 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.

然後，他們每次逐一地把這些雌狼蛛和雄狼蛛放在一起，一直觀察，直到以下三種現象的發生：雄狼蛛被吃掉；雄蜘蛛在相逢雌狼蛛之後幸免於難；或是雄狼蛛在沒有遇到雌狼蛛的情況下存活了半個小時。研究者將從未交配過的雌性狼蛛配對，或是將從未交配過得雄狼蛛於近期繁殖出來的雌狼蛛配對。並且在一系列關鍵性的實驗中，該研究團體將未交配過的雄狼蛛與實驗前兩周沒有吃果蠅的雌狼蛛配對。因為這樣條件下的雌狼蛛更為飢餓。

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. When these females laid their egg sacs, the researchers picked ten sacs at random from each group and monitored those until the eggs hatched. At that point they selected 20 spiderlings from each group for further study.

在進行了一系列的實驗之後，該研究團隊挑選了16隻雌狼蛛，而這些雌狼蛛都是之前交配後便吃掉了她們的情人。同時研究人員還挑選了10隻先前已於雄狼蛛交配過但並沒有吃掉雄狼蛛的雌狼蛛。研究團隊觀察並記錄著26隻雌狼蛛的生殖過程。而當這些雌狼蛛產下她們的蛋囊後，研究人員任意從這16隻和10隻雌狼蛛的蛋囊分別里拿出十個蛋囊，並且觀察和記錄這些蛋囊孵化的情況。所以，彭博士及其研究團隊從這兩組雌狼蛛里選出了20隻幼蛛進行進一步的實驗研究。

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. 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. Their third was that, 28% of the time, a male that had mated was indeed eaten afterwards. Successful suitors, then, succumbed more often than unsuccessful ones.

研究團隊的第一個得到的實驗現象是雌狼蛛有時吃掉跟她們交配過的雄狼蛛的時間只發生在她們分娩期的十分之一階段，而且如果雌狼蛛很飢餓的情況下，這種吃掉雄狼蛛的頻率似乎也不會增大。研究團隊第二個觀察到的現象是如果在雌狼蛛看來，一隻雄狼蛛很適合交配的話，那麼這隻雄狼蛛在和雌狼蛛交配階段就不會被吃掉---儘管交配的時間會長達一個半小時。研究團隊的第三個發現是雌狼蛛分娩期百分之二十八的時間裡，一隻曾經有過交配的雄狼蛛後來會被雌狼蛛吃掉。實驗證明，曾經交配過的雄狼蛛比沒有交配過的雄狼蛛更容易被雌狼蛛吃掉。

The crucial finding, however—which makes sense of all the others—was the success of the spiderlings. Young born of females that had eaten their partners had a 48% chance of making it through their first month of life. Those born of females who had let their partners live, had only a 12% chance of surviving that long.

然而，最為重要的發現是幼狼蛛的順利降生，這讓這發生的一切都有著意義。孵出後不久的曾經吃掉過和她們交配過的雄狼蛛的雌狼蛛有百分之四十八的可能平安的度過生命的第一個月。相反，這些曾經沒有吃掉和她們交配過的雄狼蛛的雌狼蛛僅僅只有百分之十二的機會熬過生命的第一個月。

That is a staggering difference—and certainly, in evolutionary terms, enough to drive self-sacrificial behaviour by males, since a male would have to mate successfully another three times to match the benefit he gains by this one suicidal act. 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.

無疑，這是一個頗為驚人的差異。

Just what it is that a male meal gives, via the female』s digestive system, to the hatchling spiders, remains to be determined. Perhaps spider bodies contain some crucial nutrients which are scarcer in other forms of prey. Whatever the details, though, the general answer to the biologists』 question is now clear. In the case of spiders, fathers really do lay down their lives for their children.

以雄狼蛛作為食物來源，經由雌狼蛛的消化系統，供給幼蛛的這個過程還有待考究。也許雄狼蛛自身含有的某些在其他諸多的獵物中幾乎沒有的重要的營養物質的緣故。不管這個詳細的情況是什麼，但是總體的解釋生物學家的問題的答案現在變得愈發的清晰。在蜘蛛這個大家族中，雄性蜘蛛的的確確為了他們的後代而犧牲了他們自己。