Antennal Development in the Praying Mantis (<i>Tenodera aridifolia</i>) Highlights Multitudinous Processes in Hemimetabolous Insect Species

Insects possess antennae equipped with a large number of segments (flagellomeres) on which sensory organs (sensilla) are located. Hemimetabolous insects grow by molting until they reach adulthood. In these species, the sensory structures develop and mature during each stage of development; new flagellomeres are generated at each molt elongating the antennae, and new sensilla appear. The praying mantis (Tenodera aridifolia) is a hemimetabolous insect with 7 different instars before it reaches adulthood. Because their antennae are provided with an atypical sensillar distribution, we previously suggested that their antennae develop with a different mechanism to other hemimetaboulous insect species. In the present study, we measured the number, length and width of flagellomeres along the antennae in nymph and adult mantis Tenodera aridifolia. For this study, we developed a new and innovative methodology to reconstruct the antennal development based on the length of flagellomeres. We observed and confirmed that the antennae of mantises develop with the addition of new segments at two distinct sites. In addition, we constructed a complete database of the features of the flagellum for each stage of development. From our data, we found that sexual dimorphism appears from the 6 instar (larger number and wider flagellomeres in males) in accordance with the appearance of their genital apparatus. The antennal sexual dimorphism completes at adulthood with longer flagellomeres and the emergence of a huge number of grooved peg sensilla in males during the last molting, which suggests once again their function as sex-pheromone receptive sensilla.昆虫的触角上生有大量鞭节（flagellomeres），感觉器官感器（sensilla）即分布于这些鞭节之上。半变态昆虫（hemimetabolous insects）通过蜕皮完成生长直至成虫阶段。在此类物种中，感觉结构会在每个发育阶段逐步发育成熟；每次蜕皮时均会生成新的鞭节以延长触角，同时亦会产生新的感器。螳螂（Tenodera aridifolia）属于半变态昆虫，其在达到成虫前共经历7个龄期（instar）。由于该物种的触角感器分布具有非典型特征，我们此前曾提出，其触角的发育机制与其他半变态昆虫存在差异。本研究中，我们对若虫与成虫状态下的螳螂（Tenodera aridifolia）的触角各鞭节的数量、长度及宽度进行了测量。为完成此项研究，我们开发了一种全新的创新性方法，可基于鞭节长度数据重构触角发育过程。我们观察并证实，螳螂的触角发育过程中，会在两个不同的位点新增鞭节。此外，我们还构建了覆盖各发育阶段的触角鞭节特征完整数据库。基于实验数据，我们发现，螳螂的雌雄二态性（sexual dimorphism）从第6龄期开始显现——雄性的鞭节数量更多、宽度更宽，这与其生殖器官的发育时间相契合。至成虫阶段，螳螂触角的雌雄二态性最终定型：雄性个体的鞭节更长，且在最后一次蜕皮过程中会出现大量沟槽状柄感器（grooved peg sensilla），这进一步佐证了此类感器可作为性信息素接收感器的功能。