H ave you heard the one about the wasp that kills the bug that feeds the ants that kill the crabs that keep the forests healthy on Christmas Island ? If not, that’s because it hasn’t happened yet, but it is a tale worth telling. In the coming weeks, Parks Australia will release a 2mm wasp on Christmas Island to control the island’s yellow crazy ant infestation. Crazy ants are a big threat to the island’s wildlife, including its famous red crabs. Biological control – when we use one species to control another – is infamous for giving Australia its cane toad invasion. So, how do we know this one will work? Christmas Island and its crabs Christmas Island is a unique natural habitat with many endemic species. The national park covers two-thirds of the island, which has been referred to as the Galapagos of the Indian Ocean. Many people are aware of the red crabs whose mass migration to the sea has been described as one of the wonders of the natural world. Red crabs on Christmas Island Christmas Island has many other species of crabs, including the impressive robber crabs . These may be the largest land-dwelling arthropod (the group that insects and crustaceans belong to) on earth. Together these abundant land crabs clear the forests of leaf litter and maintain burrows that prevent soil becoming compacted, creating an open and diverse forest. But this thriving natural system was disrupted when an invasive ant species became abundant on the island. The ants In the early 20th century, yellow crazy ants ( Anoplolepis gracilipes ) found their way to Christmas Island. These ants now form super-colonies, with billions of individuals across hundreds of hectares. The crazy ants spray formic acid in the eyes and leg joints of the crabs, which immobilises them. The crabs soon die and become food for the ants. In some cases, crabs that live in areas free of crazy ants are killed during their annual migration and so never return to their original forest. This creates crab-free zones even where the ants do not live. Yellow crazy ants feed on a gecko on Christmas Island. Photograph: Parks Australia/Author provided With fewer crabs, the forest has become less diverse, with a dense understory and compacted soils due to the collapse of crab burrows. Other invasive species such as the giant African land snail have become common where crabs declined. Parks Australia has been trying lots of different methods from aerial to hand-baiting to reverse the impact of yellow crazy ants on red crabs. The impact was so severe that a chemical control program targeting the super-colonies began in 2001. This program has slowed the decline of crab populations but is expensive and time-consuming, so researchers began to look into other options, including using other species. The bug: a scale insect Super-colonies of yellow crazy ants require a reliable food source and this is provided by yet another invasive species: the yellow lac scale insect ( Tachardina aurantiaca ). Scale insects (a type of true bug ) suck the sap of trees and produce a sweet secretion from their anal pore called honeydew, which ants then harvest. It seems that the super-colonies of these crazy ants could not survive without the carbohydrate-rich honeydew provided by abundant scale insects in a patch of forest. Diving scientists record 'cloud' of thousands of swarming crabs Read more There is evidence that the scale insects increase ant reproduction and make them more likely to attack other species. One large field experiment demonstrated that if we stopped the ants getting access to the scale insects, ant activity on the ground fell by 95% in just four weeks. The scale insects may need the ants as much as the ants need the scale insects. Some ants protect the scale insects in the same way that humans protect their livestock, by chasing away other predators. The interaction between these two invasive species has allowed them to build their populations to extremely high densities, something known as invasional meltdown . The good news is that scale insects, unlike ants, are amenable to biological control. For instance, Australian lady bugs were spectacularly successful in controlling the cottony cushion scale in North America. The wasp The search began to find a species that could control the scale insect on Christmas Island. And we found it: a tiny wasp known as Tachardiaephagus somervillei , which attacks the yellow lac scale insect in its native Southeast Asia. This wasp lays its eggs in mature female scale insects and kills them from the inside, producing more wasps that then lay eggs in more females. This wasp (and other predators) are so effective that the yellow lac scale insect is rare in its native habitat. Obviously, we had to test that the wasp wouldn’t attack other species. Researchers did this in the field in Malaysia, an unusual approach that yielded excellent results. The scientists exposed eight closely related scale insects to the wasp, and none were harmed. This proves that no other scale insect population on Christmas Island is at risk if the wasp is introduced, with the possible exception of another introduced scale insect that is a pest in its own right. Researchers also checked that the wasps would still work when the scale insects are being tended by yellow crazy ants – and they still attacked. After years of research it is exciting to be on the verge of releasing this wasp on Christmas Island. Postscript: the toads The stories you need to read, in one handy email Read more We all know the biological control stories that went wrong. The introduction of cane toads to control cane beetles in Australia backfired spectacularly. In Hawaii, the introduction of mongooses to control rats failed because mongooses are active during the day and the rats were active at night. In both those cases, those species were introduced without sufficient research. But these examples changed the rules and laws around introducing species. Today governments are much more aware of the risks of invasive species. Rigorous experiments and risk assessments are required before any introduction can occur. In this case, researchers from La Trobe University have worked closely with Parks Australia and the Forest Research Institute of Malaysia to collect enough data to satisfy the Australian government. We believe that this is the most closely scrutinised biological control project in Australia. When the wasps arrive on Christmas Island in a few weeks, we are confident that this will set an example for best-practice conservation. Fewer ants means more crabs, healthier trees, fewer African snails and better soil. And it will save money being spent on expensive conservation efforts for years to come. • Parks Australia has produced a special animation on the program – http://www.parksaustralia.gov.au/christmas/news/biocontrol.html . • Susan Lawler is senior lecturer, department of ecology, environment and evolution, La Trobe University • Peter Green is head of the department, college of science, health and engineering, school of life sciences, La Trobe University
《生命科学导论》课上，我跟学生们讨论，人和动物最根本的区别是什么？ 中学的政治课上讲，人类可以制造和使用工具。上网一查，会使用工具的生物很多。 有意识地种植收割庄稼、养殖家畜，说明原始人类有很强的预见性，能够脱离直接吃掉食物的本能，似乎是一个高级的特征。看看Discovery、National Geographic Channel等拍的纪录片，蚂蚁绝对可以饲养家畜，蚂蚁的家畜是蚜虫。风和日丽时，蚂蚁叼着家畜去放牧，狂风暴雨来临时，蚂蚁把它们的家畜叼到能遮风挡雨的叶子或树干下面。另外，蚂蚁还会种蘑菇。 今天Nature上的一篇论文让我们大开眼界，能放牧、种庄稼的生物多得很。 先看它的前言，除了人和蚂蚁，还有甲虫、东风螺、光鳃鱼等都会种庄稼、养家畜。 这篇论文报道的是模式生物粘菌Dictyostelium discoideum。此生物属于俗称阿米巴的原生动物，我在题目中称为小虫虫是因为它的行为象虫子。这种生物的孢子遇到适宜环境萌发后，与细菌和酵母一样，细胞快速分裂，每一个细胞就是一个个体。一旦环境中营养耗尽，细胞饿了，它们就聚集到一起变成鼻涕虫一样的东西，细胞多力量大，这个虫子可以爬很远，寻找丰富的营养或者适宜孢子传播的高地。 今天的Nature文章，David C. Queller和Joan E. Strassmann领导的课题组发现，粘菌并不是把所有细菌全部吃掉，而是留一些做种子，它们变成虫子四处游荡时携带着这些细菌，它们散发孢子时也让这些细菌散发孢子，以便把庄稼子子孙孙世代相传下去。 既然没有神经的“小虫虫”也可以种庄稼，也有传家宝，人类更没有理由因为我们的农牧业自豪了。我们真得应该认真思考：人类到底有什么了不起的呢？ 粘菌散发孢子前的结构，像小蘑菇。小虫虫站起来变成小蘑菇，是为了将孢子散发得更远。此图转自下面列举的The Scientist论文。 详情请参考Nature原文Primitive agriculture in a social amoeba. http://www.nature.com/nature/journal/v469/n7330/full/nature09668.html 或科普期刊The Scientist的报道Amoeba agriculture：Some slime molds transport and farm the bacteria they eat. http://www.the-scientist.com/news/display/57924/
我讨厌官方的一个用词， 今晚新闻联播里播的。 这个词叫群众。 我也因之想起了另一个词汇， 这个词汇叫人民。 与群众相对的词汇是什么？与人民相对的词汇是什么？ 群众这词， 使我想起 Swarm， A swarm of birds， A swarm of bees， A swarm of sheep。 而人民这个词， 使我想起serve for。 还有那句有名的关于政府的话（林肯） Ofthe people, for the people, by the people. 当下的我们呢？ 我们只是群众。 而你们只是皇帝老儿。 如《虫虫危机》里面蚂蚁与蚱蜢的关系。 这种关系在中国已延续千把年了。 不打算改改？ 还要打算将群众这种封号继续到底？ 陈永金： 别把老百姓的命当草芥！
科学家发现了一些化学物质，它们能表明一只蚂蚁还活着、并阻止它的同事把它丢到蚁群的墓地。此前的研究认为，蚂蚁把死去的同事从蚁群中移除是因为蚂蚁尸体中降解产物的积累。然而，Dong-Hwan Choe及其同事认为，蚂蚁处置组在一只蚂蚁死后1小时内就采取了行动，这远远早于降解的化学产物能够散发出来的时间。这组科学家发现，移除死蚂蚁的化学信号总是存在，但是被其他化学物质抑制，而这些化学物质在蚂蚁死后很快就消失。这组科学家使用溶剂萃取了存在于刚刚被杀死或死去1个小时的工蚁表皮中的这些化学物质。当涂抹了这些萃取物的蚂蚁蛹被放在外面的时候工蚁通常会回收蛹并把它们送回蚁巢中只有那些涂抹了来自刚刚被杀死的蚂蚁的萃取物的蛹被忽略了，没有被搬走。而其他的蛹被扔进了蚁群的垃圾堆。色谱和质谱分析表明了dolichodial和iridomyrmecin这两种化合物的存在。活的工蚁在表皮中分泌这些化合物。但是这组作者发现，如果不持续更新，在40分钟内dolichodial和iridomyrmecin或者将挥发，或者将变得失去活性。 论文# 09-01270: Signs of life: Chemical signals associated with life inhibit necrophoresis in Argentine ants, 作者Dong-Hwan Choe, Jocelyn G. Millar和Michael K. Rust，PNAS，2009
标签: 蚂蚁
