Root-knot nematode perineal pattern development: a reconsideration

The perineal pattern, a unique and complex structure located at the female posterior body region, comprises the vulva-anus area, tail terminus, phasmi ds, lateral lines and surrounding cuticular striae. Little is known about t he development of this: important but variable character complex, published information together with scanning electron and light microscopical observ ations on female development and perineal patterns were used to explain in detail the perineal pattern. The basic pattern, with fine striae, is formed just after the last moult when the vulva is induced above the anus at the posterior ventral body side. This process is likely to be influenced by the previous feeding stage. The vulva-anus region moves posteriorly, while the female is still enclosed by the old cuticle layers. After resuming feeding , the female diameter increases rapidly and pattern striae become folded an d coarser. The role of the expanding rectal glands and perineal pattern str uctures as lateral lines, anus, tail terminus and punctations are discussed in detail. Major origins for pattern variation are developmental and aging factors in both feeding stages, a vulva-anus shift and the observation of patterns of different age, in combination with variable interpretation and description.