Yanoviak Stephen P, Dudley Robert
Department of Biology, University of Louisville, 139 Life Sciences Building, Louisville, KY 40292, USA; Smithsonian Tropical Research Institute, Balboa, Panama.
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA; Smithsonian Tropical Research Institute, Balboa, Panama.
Arthropod Struct Dev. 2018 Jul;47(4):370-374. doi: 10.1016/j.asd.2017.06.005. Epub 2017 Jul 13.
Mayfly larvae generally are aquatic, but some madicolous taxa (i.e., living in thin water films) crawl over rocks within streams and waterfalls. When startled, these larvae can break the water film, jump, and enter an aerial phase of locomotion. Because mayfly larvae have been suggested as potential exemplars for the origin of insect wings as tracheal gills, and furthermore represent the most basal extant lineage of pterygotes, we analyzed jumping behavior and free-fall trajectories for one such species of mayfly (Myobaetis ellenae, Baetidae) in Costa Rica. Jumping was commonplace in this taxon, but was undirected and was characterized by body spinning at high angular velocities. No aerodynamic role for the tracheal gills was evident. By contrast, jumping by a sympatric species of bristletail (Meinertellus sp., Archaeognatha) consistently resulted in head-first and stable body postures during aerial translation. Although capable of intermittently jumping into the air, the mayfly larvae could neither control nor target their aerial behavior. By contrast, a stable body posture during jumps in adult bristletails, together with the demonstrated capacity for directed aerial descent in arboreal representatives of this order, support ancestrally terrestrial origins for insect flight within the behavioral context of either jumping or falling from heights.
蜉蝣幼虫一般生活在水中，但一些栖息于潮湿环境（即生活在薄薄的水膜中）的类群会在溪流和瀑布中的岩石上爬行。受到惊吓时，这些幼虫会冲破水膜，跳跃并进入空中移动阶段。由于有人提出蜉蝣幼虫可能是昆虫翅膀起源于气管鳃的潜在例证，而且它们代表了有翅昆虫现存最原始的谱系，因此我们分析了哥斯达黎加一种蜉蝣（Myobaetis ellenae，短丝蜉科）的跳跃行为和自由落体轨迹。在这个分类群中，跳跃很常见，但没有方向性，其特点是身体以高角速度旋转。气管鳃没有明显的空气动力学作用。相比之下，同域分布的一种缨尾目昆虫（Meinertellus sp.，石蛃目）跳跃时，在空中移动过程中始终能保持头先着地且身体姿态稳定。虽然蜉蝣幼虫能够间歇性地跳到空中，但它们既无法控制也不能瞄准自己的空中行为。相比之下，成年缨尾目昆虫跳跃时身体姿态稳定，而且该目树栖类群已证明有定向空中下降的能力，这支持了昆虫飞行起源于祖先在行为上从高处跳跃或坠落的陆地环境。
