Symbiotic relationships are widespread in nature, but the mechanisms maintaining these relationships remain to be elucidated because symbiosis incurs a maintenance cost to each participant, which lowers its reproductive rate. In host-parasite relationships, parasites are known to manipulate the host's behavior selfishly, and there is an arms race between them. Selfish manipulations also occur in symbiosis, but the effects of selfish manipulations on symbiosis are not fully understood. Here, we show that an ant-associated aphid manipulates attending ants to receive stronger protection. Aphid honeydew regurgitated by ants contains dopamine (DA). The ants showed low aggressiveness before contact with the aphids, but it rose after contact. Administration of DA to the ants increased ant aggressiveness as the concentration increased, while an antagonist of DA inhibited this effect. The other 3 amines showed no effect on aggressiveness. A previous study showed that attending ants selfishly manipulate aphids by increasing the reproductive rate of green morph to obtain high-quality honeydew. These results suggest that mutual selfish manipulation benefits both participants and is likely to strengthen symbiosis. The selfishness of each participant may contribute to sustaining this symbiosis because their selfishness increases their long-term fitness.

共生关系在自然界中很普遍，但维持这些关系的机制仍有待阐明，因为共生会给每个参与者带来维护成本，从而降低其繁殖率。在宿主与寄生虫的关系中，众所周知，寄生虫会自私地操纵宿主的行为，并且它们之间存在军备竞赛。自私的操纵也发生在共生中，但自私的操纵对共生的影响尚不完全清楚。在这里，我们展示了与蚂蚁相关的蚜虫操纵参与的蚂蚁以获得更强的保护。蚂蚁反刍的蚜虫蜜露含有多巴胺（DA）。蚂蚁在与蚜虫接触前表现出较低的攻击性，但在接触后上升。随着浓度的增加，向蚂蚁施用 DA 会增加蚂蚁的攻击性，而DA的拮抗剂抑制了这种作用。其他 3 种胺对侵袭性没有影响。之前的一项研究表明，主食蚂蚁通过提高绿色变种的繁殖率来自私地操纵蚜虫，以获得优质的蜜露。这些结果表明，相互自私的操纵对参与者都有好处，并且可能会加强共生。每个参与者的自私可能有助于维持这种共生关系，因为他们的自私会增加他们的长期健康。这些结果表明，相互自私的操纵对参与者都有好处，并且可能会加强共生。每个参与者的自私可能有助于维持这种共生关系，因为他们的自私会增加他们的长期健康。这些结果表明，相互自私的操纵对参与者都有好处，并且可能会加强共生。每个参与者的自私可能有助于维持这种共生关系，因为他们的自私会增加他们的长期健康。