State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Centre for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China.
Department of Biology II, Ludwig-Maximilians-Universität München, Biocenter, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany.
Proc Biol Sci. 2024 Apr 10;291(2020):20232546. doi: 10.1098/rspb.2023.2546. Epub 2024 Apr 3.
Fossilized mating insects are irreplaceable material for comprehending the evolution of the mating behaviours and life-history traits in the deep-time record of insects as well as the potential sexual conflict. However, cases of mating pairs are particularly rare in fossil insects, especially aquatic or semi-aquatic species. Here, we report the first fossil record of a group of water striders in copulation (including three pairs and a single adult male) based on fossils from the mid-Cretaceous of northern Myanmar. The new taxon, gen. nov., likely represents one of the oldest cases of insects related to the marine environment, such as billabongs formed by the tides. It exhibits conspicuous dimorphism associated with sexual conflict: the male is equipped with a specialized protibial comb as a grasping apparatus, likely representing an adaptation to overcome female resistance during struggles. The paired show smaller males riding on the backs of the females, seemingly recording a scene of copulatory struggles between the sexes. Our discovery reveals a mating system dominated by males and sheds light on the potential sexual conflicts of in the Cretaceous. It indicates the mating behaviour remained stable over long-term geological time in these water-walking insects.
化石化的交配昆虫是理解昆虫在深远时间记录中的交配行为和生活史特征以及潜在性冲突进化的不可替代的材料。然而，交配对在化石昆虫中特别罕见，尤其是水生或半水生物种。在这里，我们报告了一组水黾在交配（包括三对和一只单独的成年雄性）中的第一个化石记录，这些化石来自缅甸北部的白垩纪中期。新的分类单元，gen。nov。，可能代表了与海洋环境有关的昆虫中最古老的案例之一，例如潮汐形成的死水潭。它表现出与性冲突相关的明显二态性：雄性装备有特殊的胫节梳作为抓握器官，可能代表了一种适应，以克服雌性在斗争中的抵抗力。成对的 显示出较小的雄性骑在雌性的背上，似乎记录了两性之间交配斗争的场景。我们的发现揭示了一种以雄性为主导的交配系统，并阐明了白垩纪 中潜在的性冲突。这表明在这些水上行走的昆虫中，交配行为在长期的地质时间内保持稳定。
