异色瓢虫显现变种复眼的形态、显微结构及其光暗条件下的适应性变化

External morphology,microstructure and light/dark adaptational changes of the compound eyes of Harmonia axyridis ab.conspicua(Coleoptera:Coccinellidae)

复眼是昆虫的主要视觉器官,对于其寻找食物、配偶、栖息场所以及学习记忆等活动具有重要作用。本研究采用扫描电镜和石蜡切片技术对异色瓢虫显现变种Harmonia axyridisab.conspicua复眼的外部形态和内部显微结构进行了观察。结果发现:(1)复眼近椭圆形,位于头部两侧,触角窝处有缺刻,小眼表面光滑平坦,无角膜乳突结构。其雌、雄成虫复眼的小眼数分别约为705和691;(2)复眼中心区域小眼呈六边形,排列紧密,边缘区域的小眼为不规则的四边形或五边形;(3)每个小眼由角膜、晶锥、8个小网膜细胞、视杆、基膜以及色素细胞组成。晶锥由4个晶锥细胞构成,8个小网膜细胞中6个位于边缘、2个位于中央;(4)暗条件下复眼显微结构存在明显差异:光适应条件下,色素颗粒主要分布在晶锥和视杆交界处的周围,周围视杆呈环形,内、外两侧均被色素颗粒包围;暗适应条件下,色素颗粒发生纵向移动,均匀地分布在晶锥和视杆的周围,周围视杆发生扭曲呈不规则的多角形,仅外侧有色素颗粒分布。结果表明,异色瓢虫显现变种的复眼属于并列复眼,可通过色素颗粒的纵向移动以及周围视杆扭曲变形等机制来适应外界明暗环境的变化。

Compound eye is the main vision organ of insect,which plays a significant role in their foraging,finding mate and habitat,learning,memory and so on.In this study,the external morphology and internal microstructure of the compound eyes of Harmonia axyridis ab.conspicua were observed by using scanning electron microscope and paraffin section.The results indicated that：（1） the compound eye is oval,and located on the lateral upside of the head.There is a nick on the compound eye,which is near to antennal socket.The surface of the ommatidia is smooth and not covered with corneal nipples.The compound eye of the female and male consists of 705 and 691 ommatidia,respectively.（2） The ommatidia located in the central region of the compound eye are typically hexagonal,while those located in the periphery of the compound eye are often of irregular,pentagonal,and even squarish shapes.（3） The ommatidium consists of corneal lens,crystalline cone,8 retinula cells,rhabdom,basement membrane and pigment granules.The crystalline cone is composed of 4 cells.Among the 8 retinula cells,6 cells are in the periphery and the other 2 are in the centre.（4） The microstructure of compound eye of H.axyridis ab.conspicua is significant different between dark and light adaptation.In light adaptation,most of the pigment granules are distributed between the crystalline cone and rhabdoms;the peripheral rhabdom is in ring form,and its inner and outer sides are covered with the pigment granules.In dark adaptation,the pigment granules move longitudinally and are distributed on the lateral upsides of the crystalline cone and rhabdoms;the peripheral rhabdoms twist appearing as irregular polygons,and only its outer sides are covered with the pigment granules.This study reveals that the compound eyes of H.axyridis ab.conspicua are of the type of apposition eye,and they adapt to the change of light and dark by the mechanism of pigment granules moving longitudinally and rhabdoms twisting.