Andersson Johan, Borg-Karlson Anna-Karin, Wiklund Christer
Department of Chemistry, Organic Chemistry, Group of Ecological Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
Proc Biol Sci. 2004 Sep 7;271(1550):1765-70. doi: 10.1098/rspb.2003.2671.
Males of the green-veined butterfly Pieris napi synthesize and transfer the volatile methyl salicylate (MeS) to females at mating, a substance that is emitted by non-virgin females when courted by males, curtailing courtship and decreasing the likelihood of female re-mating. The volatile is released when females display the 'mate-refusal' posture with spread wings and elevated abdomen, when courted by conspecific males. Here, we assess how the amount of MeS released by courted females changes over time since mating, and whether it is influenced by the frequency with which females display the mate-refusal posture. We also assess whether males tailor the anti-aphrodisiac content of ejaculates with respect to the expected degree of sperm competition, by comparing how males allocate MeS proportionately to first and second ejaculates in relation to ejaculate mass. The results show that females housed for 5 days in individual cages where they were able to fly and oviposit normally, released similar amounts of MeS. However, females housed together for the same period of time, causing them to frequently display the mate-refusal posture, released significantly lower levels of MeS than the individually housed females. This indicates that female display of the mate-refusal posture depletes their anti-aphrodisiac stores, and suggests that females are unable to voluntarily control their release of the anti-aphrodisiac. A comparison of relative proportion of MeS transferred by males in their first and second ejaculates showed that proportionately more MeS was allocated to the first ejaculate, in accordance with the idea that these are tailored to delay female re-mating.
绿脉粉蝶（Pieris napi）的雄性在交配时会合成挥发性物质水杨酸甲酯（MeS）并传递给雌性。当未交配过的雌性被雄性求偶时，会释放这种物质，从而减少求偶行为，并降低雌性再次交配的可能性。当雌性在同种雄性求偶时展开翅膀并抬高腹部呈现“拒绝交配”姿势时，就会释放这种挥发性物质。在这里，我们评估了被求偶雌性释放的MeS量自交配后随时间如何变化，以及它是否受到雌性展示拒绝交配姿势频率的影响。我们还通过比较雄性如何根据射精量将MeS按比例分配到第一次和第二次射精中，来评估雄性是否会根据预期的精子竞争程度来调整射精中抗催情物质的含量。结果表明，在能够正常飞行和产卵的单独笼子里饲养5天的雌性释放的MeS量相似。然而，同期一起饲养的雌性，由于经常展示拒绝交配姿势，释放的MeS水平明显低于单独饲养的雌性。这表明雌性展示拒绝交配姿势会耗尽它们的抗催情物质储备，并表明雌性无法自主控制抗催情物质的释放。对雄性在第一次和第二次射精中传递的MeS相对比例的比较表明，按照旨在延迟雌性再次交配的想法，相对更多的MeS被分配到第一次射精中。
