Dipteran larvae and microbes facilitate nutrient sequestration in the Nepenthes gracilis pitcher plant host

The fluid-containing traps of Nepenthes carnivorous pitcher plants (Nepenthaceae) are often inhabited by organisms known as inquilines. Dipteran larvae are key components of such communities and are thought to facilitate pitcher nitrogen sequestration by converting prey protein into inorganic nitrogen, although this has never been demonstrated in Nepenthes. Pitcher fluids are also inhabited by microbes, although the relationship(s) between these and the plant is still unclear. In this study, we examined the hypothesis of digestive mutualism between N. gracilis pitchers and both dipteran larvae and fluid microbes. Using dipteran larvae, prey and fluid volumes mimicking in situ pitcher conditions, we conducted in vitro experiments and measured changes in available fluid nitrogen in response to dipteran larvae and microbe presence. We showed that the presence of dipteran larvae resulted in significantly higher and faster releases of ammonium and soluble protein into fluids in artificial pi...猪笼草科（Nepenthaceae）猪笼草属（Nepenthes）食肉捕虫植物的储液捕虫笼，通常栖居着被称为栖居生物（inquilines）的类群。双翅目幼虫（Dipteran larvae）是这类群落的核心组成部分，学界普遍认为它们可通过将猎物蛋白转化为无机氮，助力捕虫笼实现氮固存，但这一假说从未在猪笼草属植物中得到验证。捕虫笼体液中也定殖有微生物，但其与猪笼草之间的互作关系目前仍不明确。本研究旨在验证细毛猪笼草（N. gracilis）的捕虫笼与双翅目幼虫、体液微生物之间存在消化共生关系这一假说。研究采用模拟原位（in situ）捕虫笼环境的双翅目幼虫、猎物及体液体积体系，开展体外（in vitro）实验，检测了双翅目幼虫与微生物存在与否对体液中有效氮含量的影响。实验结果表明，双翅目幼虫的存在可使人工捕虫笼体系中的体液更快、更显著地释放铵与可溶性蛋白。