Wharton D A
Z Parasitenkd. 1986;72(6):779-87. doi: 10.1007/BF00925098.
The infective third-stage juvenile of Trichostrongylus colubriformis is surrounded by its own cuticle as well as the incompletely moulted cuticle of the second-stage juvenile, which is referred to as the sheath. The sheath comprises an outer epicuticle, an amorphous cortical zone, a fibrous basal zone and an inner electron-dense layer. The basal zone of the sheath consists of three layers of fibres; the fibres are parallel within each layer, but the fibre direction of the middle layer is at an angle to that of the inner and outer layers. The cuticle comprises a complex outer epicuticle, an amorphous cortical zone and a striated basal zone. The lateral alae of the cuticle and the sheath are aligned and overlie the lateral hypodermal cords. The lateral alae of the sheath consist of two wing-like expansions of the cortical zone with associated specializations of the inner electron-dense layer which form a groove. The cuticular lateral alae consist of two tube-like expansions of the cortical zone. The lateral alar complex of the cuticle and the sheath may maximise locomotory efficiency and prevent rotation of the juvenile within the sheath.
蛇形毛圆线虫感染性第三期幼虫被其自身的角质层以及第二期幼虫未完全蜕去的角质层所包围，后者称为鞘。鞘由外层表皮、无定形皮质区、纤维状基部区和内层电子致密层组成。鞘的基部区由三层纤维组成；每层内的纤维相互平行，但中间层的纤维方向与内层和外层的纤维方向成一定角度。角质层由复杂的外层表皮、无定形皮质区和横纹基部区组成。角质层和鞘的侧叶对齐并覆盖侧皮下索。鞘的侧叶由皮质区的两个翼状扩展以及内层电子致密层的相关特化组成，形成一个凹槽。角质层侧叶由皮质区的两个管状扩展组成。角质层和鞘的侧叶复合体可使运动效率最大化，并防止幼虫在鞘内旋转。
