LIFE-CYCLE OF LEISHMANIA-MAJOR (KINETOPLASTIDA, TRYPANOSOMATIDAE) IN THE NEOTROPICAL SAND FLY LUTZOMYIA-LONGIPALPIS (DIPTERA, PSYCHODIDAE)

The development of Leishmania major Yakimoff & Schokhor in the New Wor ld sand fly Lutzomyia longipalpis (Lutz & Neiva) was examined by light and electron microscopy. In this unnatural host, parasites differenti ated into 10 typical morphological forms, multiplied at three sites, m igrated anteriorly and established in the foregut, and attached to gut surfaces. In the blood meal, amastigotes divided and transformed into two successive dividing, stumpy promastigote stages. Elongate nectomo nad promastigotes developed from stumpy forms and subsequently rounded up in some flies into paramastigotes and opisthomastigotes. Different iation into round opisthomastigotes and the apparent fusion of paramas tigotes in the blood meal were novel observations in this study. Three nectomonad promastigotes-elongate, short, and metacyclic-were free-sw imming in the midgut lumen. Elongate nectomonad promastigotes were hig hly oriented in the midgut, with their flagella embedded between the e pithelial microvilli. Short haptomonad promastigotes were the predomin ant form attached to the intima of the stomodeal valve, whereas pear-s haped haptomonad promastigotes and paramastigotes colonized surfaces o f the esophagus and pharynx. Peripylarian attachment of promastigotes and paramastigotes in the pylorus, ileum, and colon was noted in 21% o f flies, suggesting that suprapylarian leishmanias have not lost the a bility to colonize the hindgut. L. longipalpis was a successful biolog ical host for L. major, allowing complete development of the parasite.