Meloidogyne arenaria所引起之落花生根瘤線蟲病已成為雲林地區落花生之一重要病害。採集M. arenaria同一族群之二齡幼蟲及成熟雄蟲，以掃描電子顯微鏡（SEM）觀察其頭部外部形態（包括口唇圓盤Labial disc和唇部lips之形態）以及其位置之比例，同時也分別觀察M. incognita及M. hapla同族群之二齡幼蟲及成熟雄蟲以比較其間之差異。觀察結果證明不同種（Species）間呈現不同之外部形狀。二齡幼蟲頭部環節之有無可作為種區別之特徵；M. arenaria及M. hapla無環節，而M. incognita則具有環節。M. arenaria口唇圓盤與中唇部（medial lips）形成啞鈴型而成三等分之比，而其側唇部（laterial lips）較長，頭部無環節。M. incognita二齡幼蟲口唇圓盤與中唇部連結也呈啞鈴狀，但其口唇圓盤呈顯著之圓形，頭部通常具有2∼3不規則無連續之環節。M. hapla之口唇圓盤、中唇部及側唇部均較小型，頭部無環節。成熟雄蟲掃描電子顯微鏡觀察結果顯示M. arenaria具有較隆起之口唇圓盤和弦月形之中唇部，M. incognita雖與M. arenaria頗相類似，惟其口唇圓盤特別顯著而頭部則有2∼3不完整之環節。M. hapla具有較小之長型口唇盤和中唇部。
Observation of Second-stage Juveniles and Males of Meloidogyne arenaria with Scanning Electron Microscopy
Y. H. Cheng and C. C. Tu
Peanut root-knot caused by Meloidogyne arenaria is one of the important diseases in Taiwan. The second-stage juveniles and males from one population of M. arenaria was examined by using scanning electron microscopy for observation head region, shape and proportion of labial disc and lips. Second-stage juveniles and males of one population each of M. incognita and M. hapla were also examinated for comparing species differences. The results showed that the presence or absence of annulations in the head region of juveniles is a useful differentiating character. Annulations are present in M. incognita but absent in M. arenaria and M. hapla. The labial disc of juveniles in M. arenaria is often slightly raised above the medial lips. In face view, the labial disc and the medial lips are dumbbell-shaped, and three times as long as the width of the labial disc. Laterial lips are very long. The head region is not annulated. In M. incognita, the labial disc is also prominent in the round shape. The labial disc and the medial lips are also dumbbell-shaped. The head region usually possesses tow or three irregular incomplete annulations. M. hapla secondary juveniles are characterized by the smaller labial disc, medial, and laterial lips. On male’s observation, M. arenaria possesses a raised labial disc and crescent-shaped medial lips. M. incognita is similar to M. arenaria but is characterized by a very prominent labial disc, and the head region has 2~3 incomplete annulations. M. hapla can be distinguished from other species by the small rectangular labial disc and medial lips.