Department of Entomology, Cornell University, 129 Garden Avenue, Ithaca, NY 14853, USA
Université Toulouse 3 Paul Sabatier, CNRS, ENSFEA; UMR5174 EDB (Laboratoire Évolution & Diversité Biologique), 31068 Toulouse, France.
Biol Lett. 2018 Feb;14(2). doi: 10.1098/rsbl.2017.0771.
Organisms with complex life cycles can differ markedly in their biology across developmental life stages. Consequently, distinct life stages can represent drastically different environments for parasites. This difference is especially striking with holometabolous insects, which have dramatically different larval and adult life stages, bridged by a complete metamorphosis. There is no guarantee that a parasite infecting the larval stage would be able to persist into the adult stage. In fact, to our knowledge, transstadial transmission of extracellular pathogens has never been documented in a host that undergoes complete metamorphosis. We tested the hypothesis that a bacterial parasite originally sampled from an adult host could infect a larva, then survive through metamorphosis and persist into the adult stage. As a model, we infected the host with a horizontally transmitted, extracellular bacterial pathogen, We found that this natural pathogen survived systemic infection of larvae (L3) and successfully persisted into the adult host. We then discuss how it may be adaptive for bacteria to transverse life stages and even minimize virulence at the larval stage in order to benefit from adult dispersal.
具有复杂生命周期的生物在发育生命阶段的生物学特征上可能有明显差异。因此，不同的生命阶段对寄生虫来说可能是截然不同的环境。对于完全变态的昆虫来说，这种差异尤为明显，它们的幼虫期和成虫期有很大的不同，中间有一个完全变态的过程。不能保证感染幼虫期的寄生虫能够存活到成虫期。事实上，据我们所知，在经历完全变态的宿主中，还没有记录过细胞外病原体的跨龄传播。我们检验了这样一个假设，即最初从成年宿主中分离出来的一种细菌寄生虫能够感染幼虫，然后在变态过程中存活下来，并在成虫阶段继续存在。我们以一种水平传播的细胞外细菌病原体为模型，发现这种天然病原体能够在幼虫（L3）的全身感染中存活下来，并成功地在成年宿主中存活下来。然后我们讨论了细菌跨越生命阶段，甚至在幼虫期降低毒性以从成虫传播中获益，这可能是如何适应的。
