State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.
University of Chinese Academy of Sciences, Beijing, China.
Elife. 2023 Jul 14;12:e86283. doi: 10.7554/eLife.86283.
Mermithid nematodes are obligate invertebrate parasites dating back to the Early Cretaceous. Their fossil record is sparse, especially before the Cenozoic, thus little is known about their early host associations. This study reports 16 new mermithids associated with their insect hosts from mid-Cretaceous Kachin amber, 12 of which include previously unknown hosts. These fossils indicate that mermithid parasitism of invertebrates was already widespread and played an important role in the mid-Cretaceous terrestrial ecosystem. Remarkably, three hosts (bristletails, barklice, and perforissid planthoppers) were previously unknown to be parasitized by mermithids both past and present. Furthermore, our study shows that in contrast to their Cenozoic counterparts, Cretaceous nematodes including mermithids are more abundant in non-holometabolous insects. This result suggests that nematodes had not completely exploited the dominant Holometabola as their hosts until the Cenozoic. This study reveals what appears to be a vanished history of nematodes that parasitized Cretaceous insects.
蛭形目线虫是专性的无脊椎寄生虫，可追溯到早白垩世。它们的化石记录很少，尤其是在新生代之前，因此人们对它们早期的宿主关系知之甚少。本研究报道了从中生代白垩纪缅甸琥珀中发现的 16 种与昆虫宿主相关的新蛭形目线虫，其中 12 种包括以前未知的宿主。这些化石表明，蛭形目线虫对无脊椎动物的寄生在白垩纪已经非常普遍，并在中生代陆地生态系统中发挥了重要作用。值得注意的是，有三种宿主（缨尾目昆虫、树皮虱和穿孔叶蝉目昆虫）以前无论是过去还是现在都未曾被蛭形目线虫寄生过。此外，我们的研究表明，与新生代相比，包括蛭形目线虫在内的白垩纪线虫在非全变态昆虫中更为丰富。这一结果表明，直到新生代，线虫才完全利用占主导地位的全变态类昆虫作为宿主。本研究揭示了寄生在白垩纪昆虫身上的线虫似乎已经消失的历史。
