英語聽力文摘 單親蜜蜂王國

00:00

00:00

MP3下載 文本下載

https://online2.tingclass.net/lesson/shi0529/0007/7643/393.mp3

https://image.tingclass.net/statics/js/2012

Fatherless Honeybees

How male honeybees can be without fathers? The reason lies in what’s called a haploidiploid system of sex determination. Approximately one-fifth of the animal kingdom, including ants and wasps, use this system. What it boils down to is that males are the result of unfertilized eggs whereas females are born from fertilized eggs.

But in bees there is an added complication since there is a gene that determines whether a bee will be male or female. It’s all in the numbers. Here’s how it works.

A scientist isolated a gene called CSD, or Complimentary Sex Determiner. There are 19 different versions of this particular gene. It doesn’t matter which one of these 19 versions a male inherits from his mother; he’s going to be male because of the fact that he has only one of these CSD genes.

Accordingly, a female becomes a female because she has two CSD genes, except for one catch. And that catch is a bee in the bonnet of bee breeders.

Honeybee breeders often inbreed their bees in order to ensure desired traits. However, when bees are inbred it’s possible for fertilized eggs to end up with two copies of the same version of the CSD gene. The result is that the fertilized eggs would normally develop into workers or a new queen, develop into sterilized males.

Worker bees sense these sterile males when they’re still larvae, and they kill them. Before you know it, your honeybee colony has died out. The good news is that now that scientists understand more about how sex is determined among honeybees, they may discover solutions to this problem.

沒有父親的蜜蜂

雄蜂是如何在沒有父親的情況下生存的呢?其原因在于一種叫做haploidiploid的性別鑒定系統(tǒng)。包括螞蟻王國及黃蜂帝國在內(nèi)的約五分之一的動物王國都是采用這一性別鑒定系統(tǒng)。歸根究底就是：雄性是由未受精卵繁育而來，而雌性則是由受精卵繁育而來的。

但是，這一系統(tǒng)在蜜蜂王國內(nèi)使用會比較復(fù)雜。因為蜜蜂體內(nèi)還有一個基因決定著蜜蜂的雌雄。這一切的關(guān)鍵在與數(shù)量。下面我們就來談?wù)勊侨绾纹鹱饔玫摹?/p>

科學(xué)家們從蜜蜂體內(nèi)分離出一種基因，叫做性別決定基因(簡稱CSD)。一般說來，這種基因在蜜蜂體內(nèi)會有19個版本。哪一個性別決定基因是遺傳自女蜂王的并無所謂。關(guān)鍵的是，如果說蜜蜂體內(nèi)只有一個性別決定基因的話，毫無疑問，它必定是只雄蜂。

那么，有兩個性別決定基因的就是雌性蜜蜂，但有一種蜜蜂是例外。那就是擔(dān)任著繁殖下一代重任的女蜂王了。

蜜蜂一般都是近親繁殖，以此確保下一代能具有一定的特性。然而，在進行近親繁殖時，受精卵可能會擁有兩個相同的性別決定基因的版本。自然而然的，這些受精卵會發(fā)育成為工蜂或是新一代的女蜂王，或是不育的雄蜂。

當(dāng)這些不育的雄蜂還處在幼蟲期時，若是被工蜂所發(fā)現(xiàn)，那小命也就沒了。在人們知道之前，這一蜂群已然消亡。在這里，科學(xué)家們還是帶來了一個好消息：科學(xué)家們對蜜蜂的性別決定機制已有了一定的了解，他們很快就會找出解決這個問題的方法。期待ing……

Note: a bee in the bonnet of 對……有獨特的見解/想法…