Institute for Functional Cell Morphology, Heinrich Heine University Düsseldorf, Building 26-12-00, Universitätsstrasse 1, 40225, Düsseldorf, Germany.
Sci Rep. 2022 May 6;12(1):7457. doi: 10.1038/s41598-022-11369-4.
Larvae of holometabolic insects evolved different crawling strategies depending on the presence or absence of larval legs or life style. A rather unusual mode of locomotion has independently evolved in legless larvae of several dipteran species. Maggots of the Mediterranean fruit fly Ceratitis capitata developed an effective jumping mechanism to increase locomotion speed or to deter predators during the search for suitable pupation sites. Here, we use high-speed videography to visualize even the fastest movements during jump preparation and take-off. Quantification of kinetic and biometric parameters reveal that maggots jump up to 15-fold of their body length from a standing position and gain speed with 27 times the acceleration of gravity. Videos at high spatial resolution show the mechanism of latch formation and release in unprecedented detail. Mouth hooks insert in the caudal segment and raise a cuticular fold that serves as a handle to pressurize the body prior to launch. Since locomotion behaviour should be intrinsically linked to neuromuscular systems, we dissected third instar larvae and determined the precise pattern of abdominal muscles fibres. Compared to non-jumping dipteran larvae, such as Drosophila melanogaster, the overall arrangement is highly similar, but a few muscle fibres show characteristic re-arrangements in orientation and strength that are consistent with a role in bending and jumping. These results suggest that body wall muscles show adaptations to jumping behaviour in Ceratitis larvae, and possibly also in other species with different jumping techniques.
完全变态昆虫的幼虫根据是否具有幼虫腿或生活方式而进化出不同的爬行策略。在一些双翅目物种的无腿幼虫中，独立进化出了一种相当不寻常的运动方式。地中海实蝇 Ceratitis capitata 的幼虫发展出了一种有效的跳跃机制，以提高运动速度或在寻找合适的化蛹场所时吓退捕食者。在这里，我们使用高速录像技术来可视化跳跃准备和起飞过程中甚至是最快的运动。运动学和生物计量参数的定量分析表明，幼虫可以从站立位置跳起 15 倍体长，并以 27 倍重力加速度获得速度。高空间分辨率的视频显示了闩锁形成和释放的机制，这是前所未有的详细程度。口钩插入尾部并抬起一个表皮褶皱，作为在发射前对身体加压的把手。由于运动行为应该与神经肌肉系统内在相关，我们解剖了三龄幼虫，并确定了腹部肌肉纤维的精确模式。与非跳跃双翅目幼虫（如黑腹果蝇）相比，整体排列高度相似，但一些肌肉纤维在方向和强度上表现出特征性的重新排列，这与弯曲和跳跃的作用一致。这些结果表明，体壁肌肉在 Ceratitis 幼虫中表现出对跳跃行为的适应性，在其他具有不同跳跃技术的物种中也可能如此。
