白蜡虫若虫口器超微结构特征与生态适应性

Ultrastructure of Ericerus pela(Chavannes) nymph mouthparts and ecological adaptations

超微结构表明,白蜡虫雌、雄若虫口器结构相同,均由外部的口针、下唇和唇基板,以及内部的口针囊和幕骨组成,且具有以下显著特点:(1)口器具口针囊,幕骨发达;(2)上唇退化,下唇短小、不分节;(3)下颚针具T型锁紧密相扣;(4)口器刚毛稀疏,感器单一。其中,口器上、下唇退化,幕骨发达,口针束伸缩可能主要受幕骨和口针囊控制,而口器感器退化则可能与其取食行为的高度特化有关。白蜡虫雌、雄虫口针长度和直径差异不显著(P>0.05),而1龄、2龄若虫口针长度和直径差异显著(P<0.05)。1龄若虫由于口针较短,口针束较柔软,适宜穿刺较薄的叶片,故生活在叶片上,而2龄若虫由于口针较长,口针束较为坚硬,适宜穿刺比叶片厚的树皮,故返回枝条生活,且若虫从叶片转移到枝条上生活,可能是基于寻求安全栖息地和稳定食物来源。

The ultrastructure of nymph mouthparts of the Chinese white wax scale （CWWS）, Ericerus pela, consists internally of the crumena, tentorium, the styler bundle, comprised of two mandibular stylets and two maxillary stylets, and the external clypeolabral shield, labium and sensilla. The mouthpart morphology and structures of the female nymphs are similar to the male. The mouthparts of CWWS have significantly different features in comparison to aphids and other coccids. First, the mouthparts of CWWS have a erumena and a developed tentorium. Second, the labrum is highly degraded and the labium is short and one-segmented. Third, the maxillary stylets have two ＇T＇ type locks. Lastly, the hairs of the mouthpart are sparse and the sensilla are simple. As the labrum and labium of CWWS displayed a high degree of degradation and the tentorium was found to be highly developed, the stretching of the stylet bundle was considered to be controlled by the tentoriurn and crumena together. Furthermore, the degraded sensilla may be related to a specialization of feeding behavior. There were no significant differences in the length and diameter of the stylet bundles between the female and male. However, the length and diameter of the stylet bundles were significantly different between the first instar nymphs and the second instar nymphs. The first instar nymphs had stylet fascicles that were shorter and soft and initially lived on the leaves of the host trees, presumably because the leaves were thinner and they were able to pierce the leaves while the styler bundle was relatively soft. However, the second instar nymphs had stylet bundles that were relatively hard. After the numphs molted, the degree of ossification of the stylet bundles was enhanced （increased） and the nymphs returned to the branches for living, where the strengthened stylet bundles may provide a better adaption for the thicker bark. [0]All told, the first and second stage instar CWWS nymphs switched from leaves to the branches in order to find a safe habitat and stable food source.