Rizki T M, Rizki R M, Carton Y
Department of Biology, University of Michigan, Ann Arbor 48109.
Exp Parasitol. 1990 May;70(4):466-75. doi: 10.1016/0014-4894(90)90131-u.
Eggs of three strains of the cynipid parasitoid Leptopilina heterotoma and a Tunisian strain (G317) of L. boulardi are not encapsulated by hemocytes of Drosophila melanogaster hosts, but the eggs of a Congolese strain (L104) of L. boulardi are encapsulated. To determine the reason for the difference in host response against the parasitoid eggs, lamellocytes (hemocytes that encapsulate foreign objects and form capsules around endogenous tissues in melanotic tumor mutants) were examined in host larvae parasitized by the five Leptopilina strains. Parasitization by the three L. heterotoma strains affected the morphology of host lamellocytes and suppressed endogenous melanotic capsule formation in melanotic tumor hosts. L104 did not alter the morphology of host lamellocytes nor block tumor formation in melanotic tumor mutant hosts. The morphology of some lamellocytes was affected by G317 parasitization but host lamellocytes were still capable of forming melanotic tumors and encapsulating dead supernumerary parasitoid larvae. Therefore, the eggs of strains affecting lamellocyte morphology are protected from encapsulation by the host's blood cells. L. heterotoma eggs float freely in the host hemocoel but L. boulardi eggs are attached to host tissue surfaces. Lamellocytes cannot infiltrate the attachment site so the capsule around the L104 egg remains incomplete. The wasp larva uses this gap in the capsule as an escape hatch for emergence.
三种瘿蜂科寄生蜂异角细蜂的卵以及突尼斯品系（G317）的布拉迪细蜂的卵不会被黑腹果蝇宿主的血细胞包囊，但刚果品系（L104）的布拉迪细蜂的卵会被包囊。为了确定宿主对寄生蜂卵反应存在差异的原因，对被这五个细蜂品系寄生的宿主幼虫中的片层细胞（在黑化肿瘤突变体中能包囊异物并在内源组织周围形成包囊的血细胞）进行了检查。三种异角细蜂品系的寄生影响了宿主片层细胞的形态，并抑制了黑化肿瘤宿主中内源性黑化包囊的形成。L104既没有改变宿主片层细胞的形态，也没有阻止黑化肿瘤突变体宿主中的肿瘤形成。一些片层细胞的形态受到G317寄生的影响，但宿主片层细胞仍能够形成黑化肿瘤并包囊死亡的多余寄生蜂幼虫。因此，影响片层细胞形态的品系的卵受到宿主血细胞包囊的保护。异角细蜂的卵在宿主血腔中自由漂浮，但布拉迪细蜂的卵附着在宿主组织表面。片层细胞无法渗入附着部位，因此L104卵周围的包囊仍然不完整。黄蜂幼虫利用包囊中的这个间隙作为羽化的逃生口。
