Patel M N, Wright D J
Department of Biology, Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, Berkshire, SL5 7PY, UK.
J Helminthol. 1998 Sep;72(3):257-66. doi: 10.1017/s0022149x00016539.
The ultrastructure of the cuticle of infective juveniles (IJs) of Steinernema carpocapsae (newly emerged and 80-day-old) and newly emerged IJs of S. riobravis, S. feltiae and S. glaseri was examined using transmission electron microscopy. The thickness of four distinctive layers of the cuticle was measured: epicuticle, cortical and median layer, striated layer and fibrous mat. The thickness of the cuticle was correlated with the size of the IJ. In the case of newly emerged IJs, the smallest species, S. carpocapsae, had a cuticle thickness of c. 270 nm compared with c. 460 nm for S. glaseri, the largest of the four species. The overall thickness of the cuticle or the thickness of the cuticle layers was not correlated with the ability of the IJs of the four species to survive desiccation per se. The major difference between newly emerged IJs of the four species was that S. carpocapsae had a proportionately thicker striated layer compared with the other three species. The significance of this is not known but it may be an adaptation involving the nictation behaviour of this species. A substantial change was observed in the cuticle of aged (80-day-old) IJs of S. carpocapsae, whereby the thickness of the cortical and median layer increased by more than 100% and the overall thickness of the cuticle increased by about 50%. Two possible explanations for this increase are: (i) new material was synthesized; or (ii) the fluid content of this layer increased due to an increase in the permeability of the outer layers of the cuticle. The ultrastructure of the sheaths of S. feltiae and S. glaseri was also examined and, apart from S. glaseri having a thicker sheath, the structure of the sheath in both species was similar, with the epicuticle and striated layer still visible.
利用透射电子显微镜对新羽化及80日龄的小卷蛾斯氏线虫感染性幼虫（IJ）以及新羽化的里奥布拉沃斯斯氏线虫、费氏斯氏线虫和格氏斯氏线虫的角质层超微结构进行了研究。测量了角质层四个不同层的厚度：表皮层、皮质层和中层、横纹层和纤维垫。角质层厚度与感染性幼虫的大小相关。对于新羽化的感染性幼虫，最小的物种小卷蛾斯氏线虫的角质层厚度约为270纳米，而四种线虫中最大的格氏斯氏线虫的角质层厚度约为460纳米。角质层的总厚度或角质层各层的厚度与这四种线虫感染性幼虫本身的耐干燥能力无关。这四种线虫新羽化的感染性幼虫之间的主要差异在于，与其他三个物种相比，小卷蛾斯氏线虫的横纹层相对较厚。其意义尚不清楚，但可能是该物种涉及点头行为的一种适应性变化。在小卷蛾斯氏线虫老龄（80日龄）感染性幼虫的角质层中观察到了显著变化，皮质层和中层的厚度增加了100%以上且角质层总厚度增加了约50%。这种增加可能有两种解释：（i）合成了新物质；或（ii）由于角质层外层通透性增加，该层的液体含量增加。还研究了费氏斯氏线虫和格氏斯氏线虫鞘的超微结构，除了格氏斯氏线虫的鞘较厚外，两个物种鞘的结构相似，表皮层和横纹层仍然可见。
