两种飞行方式的甲虫胸部结构比较形态学研究

Comparative morphological study on the thorax structure of beetles in two flight modes

【目的】大部分甲虫飞行时张开鞘翅,伸出后翅飞行;多数花金龟和部分蜣螂类群在飞行时采取鞘翅闭合,同时抬起侧缘,伸出后翅的方式飞行。然而关于这种高效飞行方式受哪些影响因素的研究较少,胸部结构对飞行方式的影响有待探究。【方法】本文选取不同飞行方式的2科共9种甲虫的前胸背板、中胸背板、后胸背板、中胸腹板、后胸腹板、中胸侧板、后胸侧板结合传统形态学和三维模型重建技术进行比较分析,探究胸部结构与飞行方式的关联。【结果】近缘类群的甲虫胸部结构相似。闭合鞘翅飞行的甲虫,前胸、鞘翅隆拱程度低,鞘翅具有缺刻且肩部外凸,中胸背板骨化程度高,中胸后侧片发达,侧翅突较短,鞘翅基部腋片具有融为一体的趋势;相应的张开鞘翅飞行的甲虫,前胸、鞘翅隆拱程度高,鞘翅卵圆形,中胸背板骨化程度低,中胸后侧片不发达,侧翅突较长,鞘翅基部腋片结构分明。【结论】闭合鞘翅飞行的甲虫前胸和鞘翅隆拱程度低,可能更符合空气动力学;骨化程度高的中胸背板、外凸的鞘翅肩部和发达的中胸后侧片在物理层面上限制了鞘翅的张开;侧翅突短小可能使后翅运动更高效。总言之两种飞行方式的甲虫具有胸部形态上的差异,这些形态上的差异既受飞行选择压力的影响,也受演化过程中亲缘关系远近的影响。

[Aim]Most beetles fly with their elytra open and their hind wings spread.However,most rose chafer and some dung beetle species fly by closing their elytra,elevating their side edges,and spreading their hind wings.From an aerodynamic perspective,flying with a closed elytra reduces air drag and is more efficient.Recent studies have established that the well-developed muscles and wings of the thorax are crucial for improving the flight ability of beetles,and the axillary joints of the hind wings play a key role in the flight of scarab beetles.However,research into the factors influencing this efficient flight mode and how the thoracic structure impacts flight modes remain limited.[Methods]To explore the relationship between thoracic structure and flight mode,a comparative analysis was carried out on the morphology of the pronotum,mesonotum,metanotum,mesopleuron,metapleuron,elytra,mesosternum,and metasternum of nine beetle species from two families that utilize different flight modes.[Results]In beetle species that fly with closed elytra,several distinct features were observed.The pronotum and elytra have lower arches,while the elytra are characterized by concaved edges and convex shoulders.The mesonotum is strongly sclerotized and the epimeron well-developed.The pleural wing process of the metapleuron is short,and the axillary segments of the base of the elytra tend to be integrated.In contrast,beetles that fly with open elytra,have strongly arched pronotum and elytra.The elytra are oval and the mesonotum is less sclerotized.The epimeron is undeveloped,the pleural wing process is longer,and the base axillary segments of the elytra are clearly structured.The thorax structure of beetles in related groups is similar.[Conclusion]Beetles that fly with closed elytra have lower pronotum and elytra arches that may be have better aerodynamic effect compared to beetles that fly with open elytra.The significant sclerotization of the mesonotum,along with the protruding elytra shoulder,and developed epimeron all limit the expansion of the elytra from structural side.In summary,the two flight modes of beetles have distinct differences in the thoracic morphology and may influenced by both flight selection pressures and phylogenetic status.