在秘魯雨林的深處，一種蜣螂將自己的身份從清道夫變成了殺手,。與成千上萬的同胞兄弟不一樣,，這種小蟲子竟然不愛吃臭烘烘的糞便，而是會將千足蟲撕成兩段,，并以它們的內(nèi)臟為食,。在動物王國中，這種食性上的戲劇性變化極為罕見,，從而使其成為生物進化的一個完美例證,。
當蜣螂對動物的糞便大快朵頤時，它們實際上是在尋找構成這些排泄物的大量細菌,。不管你相不相信,，這是一種競爭激烈的生活方式，在某些地方,，80種蜣螂會為了同樣的糞便而大打出手,。美國普林斯頓大學的生態(tài)學家Trond Larsen認為，這或許就是迫使某一種蜣螂（Deltochilum valgum）與過去的最愛說再見的真正原因。
出于對生活在秘魯雨林中的許多種蜣螂的食性的興趣,，Larsen和他的同事用糞便,、腐肉、水果和菌類做誘餌,。研究人員同時還用活的千足蟲吸引蜣螂,，這是因為Larsen之前曾經(jīng)看到過一些蜣螂以千足蟲的尸體為食。經(jīng)過11個月,，研究小組記錄了132種蜣螂以及超過10萬只個體的食性,。他們發(fā)現(xiàn)，Deltochilum valgum是唯一以千足蟲為食的蜣螂,。研究人員在最近的《生物學快報》網(wǎng)絡版上報告了這一研究成果,。
更讓研究人員吃驚的是Deltochilum valgum攻擊千足蟲的方式。利用紅外攝像機,，Larsen觀察到一只8毫米長的Deltochilum valgum會將自己生有鋸齒的頭部楔入千足蟲的體節(jié)中,，直至最終將獵物的身體撕裂為兩段。隨后,，這種蜣螂便會肢解千足蟲的剩余部分并分而食之,。Larsen解釋說，Deltochilum valgum之所以能夠殺死體長是自身13倍的千足蟲,，完全是因為體型微妙變化的結果,，包括其楔形的頭部以及適于抓住千足蟲并將其撕碎的后腿。
Larsen指出,，這些改變?yōu)椴妒承则掾胄路N的迅速暴發(fā)創(chuàng)造了可能性,。事實上，在他的發(fā)現(xiàn)公布之后,，Larsen又觀察到幾個以千足蟲為食的Deltochilum亞種,。
美國布盧明頓市印第安納大學的生物學家Armin Moczek認為，這真是一個“相當引人入勝的發(fā)現(xiàn)”,。但是Moczek指出,，千足蟲體內(nèi)具有很高比例的糞便，這是因為它們以腐爛的植物為食,。因此他推測,，如果這種蜣螂以千足蟲的內(nèi)臟為食，那么它們實際上還是在吃糞便,。（生物谷Bioon.com）
生物谷推薦原始出處：
Biology Letters DOI：10.1098/rsbl.2008.0654
From coprophagy to predation: a dung beetle that kills millipedes
Trond H. Larsen1, Alejandro Lopera2, Adrian Forsyth3, Fran?ois Génier4
1Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
2Department of Biology, University of New Orleans, New Orleans, LA 70148, USA
3 Blue Moon Fund, Charlottesville, VA 22902, USA
4 401-60 Rue du Minervois, Gatineau, Québec, Canada J9H 7M1
The dung beetle subfamily Scarabaeinae is a cosmopolitan group of insects that feed primarily on dung. We describe the first case of an obligate predatory dung beetle and contrast its behaviour and morphology with those of its coprophagous sympatric congeners. Deltochilum valgum Burmeister killed and consumed millipedes in lowland rainforest in Peru. Ancestral ball-rolling behaviour shared by other canthonine species is abandoned, and the head, hind tibiae and pygidium of D. valgum are modified for novel functions during millipede predation. Millipedes were killed by disarticulation, often through decapitation, using the clypeus as a lever. Beetles killed millipedes much larger than themselves. In pitfall traps, D. valgum was attracted exclusively to millipedes, and preferred injured over uninjured millipedes. Morphological similarities placing D. valgum in the same subgenus with non-predatory dung-feeding species suggest a major and potentially rapid behavioural shift from coprophagy to predation. Ecological transitions enabling the exploitation of dramatically atypical niches, which may be more likely to occur when competition is intense, may help explain the evolution of novel ecological guilds and the diversification of exceptionally species-rich groups such as insects.
