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原文
The nature of thisrelationship is puzzling. It isdifficult to discern how carrying anotherorganism around can be advantageous.We speculated that in fact, amphipods mustbe considerably slowed down. Bycarefully measuring the swimming speeds ofamphipods with and without seabutterflies, we found that amphipods carrying seabutterflies moved only halfas quickly as similarly sized solitary amphipods.The situation simply made nosense. In reducing their mobility, the amphipodsbecame more vulnerable topredators and less adept at capturing prey. Why, then,would amphipods go outof their way to abduct and carry sea butterflies?
Our experimentsclearly demonstrated that something aboutthe sea butterflies was repelling thefish, and we suspected that thisdeterrence was chemical. To find out, weconducted a second set of feedingexperiments. We homogenized the seabutterflies and mixed the homogenate withfish-meal powder to make foodpellets. As a control, we also made food pelletscontaining just the fish-mealpowder. We offered both the experimental and thecontrol pellets to fish, whichalways ate the control pellets and alwaysrejected the pellets containing thehomogenate. This provided compellingevidence that compounds might beresponsible for the feeding chemicaldeterrence.
中间删去一段~没什么用
Our experimentsdemonstrated to us that the sea butterflyC. antarctica synthesizes a deterrentsubstance that the amphipod H. dilatataexploits for its own protection. Thisunique association - the abduction of onespecies by another - is unprecedentedin the annals of behavioral and chemicalecology. Some decorator crabs arechemical ecology known to cover their uppercarapace with a variety of objects,including the occasional sponge that mightharbor defensive chemistry. But thisappears to be a nonselective behavior.Crabs haphazardly decorate themselveswith whatever is at hand.
The associationbetween the sea butterfly and the amphipodfalls within the definition ofsymbiosis共生, where twodissimilar species livetogether in an intimate association. However, none ofthe relationships definedwithin the broad context of symbiosis - parasitism,comensalism or mutualism -appear to suitably describe the seabutterfly-amphipod relationship.
Parasitism寄生 implies that one speciesassociateswith another to the detriment伤害of one of them. Often, the parasite feeds off the tissues or bodyfluids of itshost. Mutualism共生describes a relationship where both species benefit from theassociation.Commensalism describes organisms that live in benign and neutral中立or良性association with one another. Neither of the latter twointeractionsappropriately describes what we have observed, and parasitismprovides only avery weak analogy to it. We feel that a new term might be neededto describethe "antagonistic symbiosis" that seems to describe mostaccuratelythis unique interaction.
寄生:一个伤害另一个，吃对方组织和体液。共生:双方都获利。commensalism共栖:中立，互相不干扰。实际(如果加上下一段的文章):一个获利，另一个间接受害,若没有下面这段,得看选项怎么说了.网上的定义是theassociation isdisadvantageous or destructive to one of the organisms, butordinarily it isused of cases where the association is advantageous, or oftennecessary, to oneor both, and not harmful to either.
In thisassociation the antagonist benefits greatly fromthe relationship. Remember thatthe amphipod must sacrifice its mobility andspeed. Clearly the defense itacquires offsets these drawbacks. The seabutterfly, on the other hand, is atthe mercy of the amphipod. While it isbeing carried around, it cannot feed tosustain its energy |
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发表于 2012-4-5 21:27:25
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