那些采摘漿果的人要小心了,?？茖W(xué)家日前發(fā)現(xiàn)了一種能夠傳染給大滑行蟻(Cephalotes atratus)的寄生蟲,。這種寄生蟲能夠使螞蟻的尾部變得又紅又亮，看起來(lái)就像一顆熟透了的漿果（如上圖）,。
據(jù)美國(guó)《科學(xué)》雜志在線報(bào)道,，這些寄生蟲還會(huì)產(chǎn)下數(shù)百枚卵，并使得螞蟻的尾部在空氣中搖擺,。這種方法會(huì)引誘小鳥吃下這些“漿果”,，從而使寄生蟲隨著小鳥的糞便傳播。接下來(lái),，螞蟻又會(huì)搜集鳥兒的糞便,，并用這些糞便給后代喂食，從而又開始了一個(gè)新的循環(huán),。這是寄生蟲利用模擬漿果進(jìn)行傳播的第一個(gè)例證,。研究小組將在4月份出版的《美國(guó)博物學(xué)家》（The American Naturalist） 雜志上報(bào)告這一研究成果。（科學(xué)時(shí)報(bào) 群芳/編譯）
（《美國(guó)博物學(xué)家》（The American Naturalist）,，Vol 171:April 2008,，S. P. Yanoviak, R. Dudley, G. Poinar, Jr.）
英文原文：
Parasite-induced fruit mimicry in a tropical canopy ant
S. P. Yanoviak (Florida Medical Entomology Laboratory), M. Kaspari (University of Oklahoma), R. Dudley (Smithsonian Tropical Research and University of California, Berkeley), and G. Poinar, Jr. (Oregon State University)
(Vol 171:April)
Moving from one host to another—a critical stage in many parasite life cycles—presents an enormous logistical obstacle for many parasitic species. One common strategy to overcome this problem is for the parasite to change the appearance or behavior of the intermediate host so that it is more attractive to predatory terminal hosts. A team of scientists working high in the canopy of tropical rain forests of Panama and Peru recently discovered an amazing example of this phenomenon: a new species of parasitic nematode, Myrmeconema neotropicum, modifies its host ants such that they resemble ripe fruits. Research conducted by Steve Yanoviak (University of Arkansas at Little Rock), Michael Kaspari (University of Oklahoma), Robert Dudley (University of California, Berkeley), and George Poinar, Jr. (Oregon State University) suggests that the infected ants are attractive to and are consumed by frugivorous birds, which subsequently transmit the nematodes to new colonies via their feces.
The unfortunate ants in this case are workers of the Neotropical canopy species Cephalotes atratus, which recently became famous for their aerial gliding ability. Whereas normal C. atratus workers are completely black, parasitized ants have bright red gasters, the globular rear ends of ants. The red gasters of infected ants contain hundreds of nematode eggs and are much easier to pluck from the ant's body than the gasters of normal ants. Moreover, infected ants walk with their gasters in a conspicuous elevated position, and ants become sluggish and less defensive in the latter stages of infection. Thus, a duped frugivorous bird could easily pluck the gaster from a parasitized ant. Given that bird feces are commonly collected by foraging C. atratus workers, birds provide a reliable mechanism for transmitting the parasite to new ant colonies. Once inside a colony, the parasitic worms develop inside the ant larvae.
Red-gastered C. atratus were mistakenly described as a separate taxonomic variety over a century ago, and they have since appeared in many museum collections. "Like other ant biologists, I initially thought this was another species of Cephalotes," says Kaspari. "Robert didn’t think so and we made a bet over beers. Then Steve opened one up under the scope and–Wow! I lost the bet," Kaspari admits.
This is the first report of parasite-mediated fruit mimicry in an arthropod, and provides an amazing example of the complexity of host-parasite interactions. It also shows how finely-tuned such interactions may become. In this case, the reddening of the ant gaster is very closely linked to both the development of the parasite and to normal changes in the ant's behavior over time: the infected ant most closely resembles a ripe berry only when the parasites are fully developed, which corresponds to the period in the ant's life when it is working as a forager, and therefore spending large amounts of time outside the nest.
