科学家发现西班牙工蚁自己决定谁做蚁后
 
作者：新京报 文章来源：新京报 更新时间：2010-11-15
 

以往我们都觉得，蚂蚁都是勤勤肯肯干活儿的工人，虽然它们在窝外老和别的蚂蚁开战，但是窝里面都好和谐好和谐啊，工蚂就是螺丝钉，根本不知权力是个什么东西。但是近日英国科学家发现，有的蚂蚁可有革命性了。
 
老知识 能生产的为王
 
要说明这个问题，首先要从蚂蚁的社会组成说起。
 
蚂蚁的社会有蚁后、工蚁和兵蚁的分工。工蚁在蚂蚁社会里干各种工作，兵蚁只管打打杀杀。工蚁在蚂蚁社会里起主要作用，很多种蚂蚁根本没有兵蚁，所以下面主要说蚁后和工蚁。
 
蚂蚁的社会准则就是“掌握生产力者为王”，这里的“生产力”就是生孩子的能力。蚁后就是能下蛋的蚂蚁，工蚁负责照顾它。蚁后每隔一段时间会产下一批长翅膀的繁殖蚁，这些繁殖蚁包括雌蚁和雄蚁，雄蚁就是个生殖机器，和别的窝的雌蚁一夜欢娱之后就死掉了；而雌蚁会自己挖个巢产卵，逐渐做成蚁后。
 
那么，为什么工蚁在蚁后面前会“低三下四”呢？其实，蚁后、工蚁、兵蚁的基因型都是一样的，只是在还是幼虫的时候吃的东西不一样。也就是说，如果小时候给吃点好的，工蚁也能生孩子，在蚁群里称王。事实上，确实有些工蚁也有生殖能力。
 
我们知道，动物的一切活动都被其基因控制，它生活的目的就是为了把自己的基因传下去。那么工蚁为什么要让蚁后生孩子，而自己不生孩子呢？关于蚂蚁奇特的“无私”行为有多种解释。一种说法是因为工蚁的爸爸——雄蚁是单倍体，所以经过计算，一只工蚁和蚁后产下的姐妹有3/4的基因是一样的，如果它自己生孩子，只有1/2的基因和自己是一样的，所以自己生孩子还不如养老妈生下的孩子合算。不过也有科学家反对这种说法，他们觉得蚂蚁的社会性并不是因为爸爸是“单倍体”这个特殊事实，而符合社会性动物的一些一般模式。
 
在以前，科学家们都以为，工蚁长成之后，看看自己生不出孩子来，就会对能生孩子的蚁后低三下四。但近期研究者发现，有时工蚁很有革命性，它们不中意的蚁后，能生孩子也要拉下王座！
 
新发现 工蚁能“选”蚁后
 
这项研究是由莱切斯特大学生物系的罗伯特·哈蒙德（Robert Hammond）博士和理查·吉尔（Richard Gill）博士负责的，研究成果在《皇家学会学报B》（Proceedings of the Royal Society B）上。
 
他们发现，工蚁的社会地位并不像以前认为的那样低，工蚁在建立一个秩序井然的，矛盾最小化的社会的过程中发挥着关键作用。莱切斯特的团队发现，当西班牙的细胸蚁（Leptothorax acervorum）会自己决定谁当它们的蚁后。哈蒙德说：“我们发现工蚁确实有这种权力，就像造反的农民一样。这些暴民很残忍，工蚁会打压能够繁殖的蚁后，甚至把它们杀掉，只有唯一的蚁后能够产生后代。”
 
难道蚂蚁的窝里还能容得下多个蚁后吗？莱切斯特的研究者说：能！他们发现，在英国的，法国和德国以及很多其他地方的细胸蚁，工蚁对窝里所有能繁殖的蚂蚁都没有任何恶意，每个都被捧成蚁后，多个蚁后都能产生后代。在这种情况下，蚂蚁的领地是由多个家庭组成的，而不是像西班牙那样，是由一个个单独的家庭组成的。事实上，这种情况在蚂蚁中很常见。
 
科学家们对于同种蚂蚁之间这种有趣的差异很感兴趣。吉尔博士说：“我们知道包括人类在内的许多动物生活在社会团体中，成员之间经常会发生矛盾。蚂蚁有自然界最完整和复杂的社会，明白他们的社会冲突是如何解决将会带来很大好处。由于蚂蚁已经在复杂的社会中生活了几百万年，它们已经发展了解决问题的机制。”
 
莱切斯特大学的小组试图找出蚂蚁如何解决“谁来统治领地”的争端。他们的研究范围不仅局限于蚂蚁，而是包括所有群居动物。在猫鼬的社会，只有一些雌性会产生后代，裸地鼠也是如此，但是狮子的社会中，所有的雌性都会繁殖后代。之所以研究这么一大堆动物，就是为了帮助人们理解为什么在群居动物中，“由谁来繁殖下一代”这个问题会有如此多的差异。
 
大用处 帮助防治入侵蚁
 
这项研究还有一种很实用的目的。哈蒙德博士说：“一些蚂蚁是害虫，特别是一些作为入侵物种的蚂蚁——它们入侵了其他的国家，甚至大洲的生态环境。它们具有极大的破坏性，引起了巨大的损失。”比如说在世界很多国家为害的“火蚁”，它们最大的特点是会“蜇”人。一般的蚂蚁都是咬破其他动物的皮肤，然后用嘴把蚁酸注入伤口中，而火蚁会咬住其他动物，然后用腹部上的蜇针蜇它们。火蚁蜇人会让人非常疼痛，痛感和烧伤后的痛感很类似，“火蚁”之名由此而来。最有名的一种火蚁是所谓的“红色引入火蚁”，它是1918年由一艘来自南美的货船无意间引入美国的，后来在美国南部和西南部泛滥成灾。
 
我们会发现，在莱切斯特大学的研究中，英国的细胸蚁和西班牙的细胸蚁的社会行为不同。科学家们希望通过研究蚂蚁社会行为的不同，还研究蚂蚁生活环境变化和社会结构的关系，或者社会结构的变化是否会引起蚂蚁入侵别的区域，这对防治蚂蚁的危害有着重要的作用。

Workers Hold Key to Power in Nature's Oldest Societies, Ant Study Shows

ScienceDaily (Nov. 3, 2010) — A new study analysing how complex, highly-evolved societies are organised in nature has found that it is workers that play a pivotal role in creating well-ordered societies where conflict is minimised. For when it comes to determining who reproduces in ants, University of Leicester biologists have found the humble worker is queenmaker -- it is they who choose their queen.

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This information is key to understanding the evolution of complex interdependent societies -- over 100 millions years old -- that have evolved mechanisms ensuring stable cohabitation and conflict resolution.

What the Leicester team discovered surprised them: While Spanish worker ants were ruthless in determining who became their queen -- and hence acquired the right to reproduce -- the same species of ants in France, Germany and the UK are known to be more 'apathetic'.

While Spanish workers bullied or even killed rival queens in order to choose their queen, UK workers are not aggressive at all and were loyal subjects to any number of queens.

The research by Dr Robert Hammond and Dr Richard Gill of the University of Leicester Department of Biology is published in Proceedings of the Royal Society B. The study was funded by the Natural Environment Research Council.

The finding could have important applications. Dr Hammond said: "Some ants are pests, and in particular invasive ants -- that have colonized new countries and continents -- are very destructive causing many millions of pounds of damage. In a number of important cases ants have invaded because of a shift in their social organisation. So understanding the reason for differences in social organisation in a non invasive species is likely to help understand these problem species."

The four-year study reveals that Spanish ant societies are composed of single family units where only one queen rules the roost -but UK ant societies are a more complex mixture of family units where lots of queens are having offspring

Spanish worker ants are truly revolutionary, the research found,while UK worker ants are more 'apathetic'.

Dr Gill said: "Many animals -- including humans -- live in social groups and, as we all know, the interests of group members are often in conflict and 'arguments' often break out. Ants have some of the most integrated and complex societies found in nature and it is of great interest to understand if there are conflicts within their societies and how they are resolved. Because ants have been living in complex societies for many millions of years, and cooperation is highly important to their success, mechanisms that resolve such arguments should have evolved."

"We sought to find out how the argument over who heads ant colonies is settled. This argument about who reproduces is not just confined to the ants we study, but is a general issue in socially living animals. In meerkats, only a few females reproduce, likewise in naked mole rats only a single 'queen' mole rat reproduces, yet in lions all females reproduce in a social group. The aim of this work is to help explain why we see such variation in who reproduces in socially living animals."

The Leicester researchers studied the 'twig ant' -- Leptothorax acervorum -- that have more than one queen per nest (this is actually quite common in ants). However, in the Spanish population only one queen reproduces -- even though other queens in the nest are capable.

"We found evidence that workers do indeed hold the power -- and, like revolting peasants -- the masses are ferocious with workers beating up -- even killing -- all but one queen who they preferentially groom and who ends up reproducing" Dr Hammond said.

But this 'worker power' is not found in all populations of twig ants. In fact in twig ant colonies from the UK, France and Germany and many other places -- workers are not aggressive to queens at all and multiple queens end up reproducing. The colony in these cases is an assemblage of multiple families, rather than a single family as found in Spain.

Dr Hammond said: "Worker ants are known to be important players in various arguments that happen within the colony, but this is the first time worker ants have been shown to be so influential over which queens reproduce. Also, the contrast in worker power between the aggressive Spanish twig ant workers and the apathetic twig ant workers found in the UK and elsewhere is intriguing.

"The role of workers has been overlooked in the argument over who determines which queens reproduce. Also, a particular species is often thought to have fixed social organisation. This work shows that species can vary in fundamental aspects of how their societies are organised."

While this study has established that in Spanish colonies of this ant it is worker behaviour that determines which queens reproduce researchers have yet to determine the ultimate reason why workers behave like this, and also why worker behaviour varies.

"We need to establish to what extent it is nature (genes) and nurture (environment) that is responsible for the difference in behaviour between Spanish and UK ants."

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Leicester, via EurekAlert!, a service of AAAS.

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Journal Reference:

Richard J. Gill, Robert L. Hammond. Workers influence royal reproduction. Proceedings of the Royal Society B, 2010; DOI: 10.1098/rspb.2010.1774