小贯小绿叶蝉(Empoasca onukii)的生长发育对自身视觉能力的影响

Effects of Growth and Development on the Visual Ability of Empoasca onukii

异速生长普遍存在于昆虫的生长发育过程中,是昆虫适应外界环境的重要策略。视觉线索是小贯小绿叶蝉(Empoasca onukii)寄主选择和飞行运动的关键信息,随着叶蝉龄期的增长,叶蝉的体型和活动能力逐渐增强,同时复眼的形态也发生显著变化。通过组织学和行为学技术,测定叶蝉不同龄期复眼形态结构和视觉能力的变化特征,明确了叶蝉的视觉能力在生长发育过程中逐渐增强,从1龄至5龄,若虫的光学灵敏度从0.04μm^(2)·sr提升至0.11μm^(2)·sr,视觉敏锐度从0.086 cpd(Cycles per degree,周/度)提升至0.112 cpd,均符合异速生长规律,但增速慢于若虫体型的增长速度。若虫羽化后复眼中部区域的光学灵敏度下降且雌雄虫存在显著差异,虽然成虫的视觉敏锐度有所提升,但依旧属于低分辨率视觉,有效视距非常有限。本研究证实了叶蝉为了优先体型及其运动相关器官的发育,视觉能力增长速度选择放缓且主要注重复眼视野的增加,以便于叶蝉感知大范围的视觉线索。

Allometry is an important strategy for insects to adapt to the surrounding environment.Visual cues are the key information for host selection and flight movement of Empoasca onukii.With the growth and development of E.onukii,the size and mobility of the leafhopper gradually increase,and the morphology of the compound eye also changes significantly.In this study,histological and behavioral methods were used to determine the morphological structure and visual ability of the compound eye of E.onukii at different ages.The results show that the visual ability gradually increased during the growth and development process of E.onukii.From 1^(st) instar to 5^(th) instar,the optical sensitivity of the nymph increased from 0.04μm^(2)·sr to 0.11μm^(2)·sr,and the visual acuity increased from 0.086 cycles per degree (cpd) to 0.112 cpd.Both of optical sensitivity and visual acuity were consistent with the allometric growth,but their growth rates were slower than that of the size of nymphs.After the emergence of nymphs,the optical sensitivity of the center region of the compound eye decreased and there was a significant difference between the male and the female.Although the visual acuity kept increasing,the compound eye of E.onukii was still a low-resolution organ with limited effective visual distance.This study confirms that E.onukii slows down the growth rate of visual ability to prioritize the development of body size and motion-related organs,and focuses on the increase of visual field to facilitate to perceive visual cues in a wide range.