No evidence for behavioural adaptations to nematode parasitism by the fly Drosophila putrida

Behavioural adaptations of hosts to their parasites form an important component of the evolutionary dynamics of host–parasite interactions. As mushroom-feeding Drosophila can tolerate deadly mycotoxins, but their Howardula nematode parasites cannot, we asked how consuming the potent mycotoxin α-amanitin has affected this host–parasite interaction. We used the fly D. putrida and its parasite H. aoronymphium, which is both highly virulent and at high prevalence in some populations, and investigated whether adult flies utilize food with toxin to prevent infection in the next generation or consume the toxin to reduce the virulence of an already established infection. First, we found that uninfected females did not prefer to eat or lay their eggs on toxic food, indicating that selection has not acted on the flies to alter their behaviour towards α-amanitin to prevent their offspring from becoming infected by Howardula. However, we cannot rule out that flies use an alternate cue that is assoc...宿主对寄生虫的行为适应性，是宿主-寄生虫相互作用进化动力学的重要组成部分。食菇果蝇（mushroom-feeding Drosophila）能够耐受致命的真菌毒素，但其体内的霍华德线虫（Howardula nematode）寄生虫却无法耐受此类毒素。据此我们提出研究问题：摄入强效真菌毒素α-鹅膏蕈碱（α-amanitin）会如何影响这一宿主-寄生虫互作关系。我们选用了臭果蝇（D. putrida）及其寄生虫异形霍华德线虫（H. aoronymphium）——该寄生虫在部分种群中致病力极强且感染率颇高——并探究了成年果蝇是否会利用含毒素的食物以阻止下一代子代遭受感染，或是通过摄入毒素来降低已建立感染的致病力。首先，我们发现未感染的雌蝇并不会优先选择在有毒食物上进食或产卵，这表明自然选择并未作用于果蝇，使其改变对α-鹅膏蕈碱的行为偏好，以避免子代被霍华德线虫感染。然而，我们无法排除果蝇会利用其他关联线索的可能性……