Development of Leishmania mexicana in Lutzomyia diabolica and Lutzomyia shannoni (Diptera: Psychodidae)1

Abstract

Extrinsic development of Leishmania mexicana was observed in two anthropophilic sand flies, Lutzomyia diabolica (Hall) and Lu. shannoni (Dyar). First indication of development of ingested amastigotes appeared between 18 and 24 h postfeeding, when light to moderate infections of short, ovoid, slightly motile forms with short flagella were seen undergoing binary fission within the intraperitrophic space of the abdominal midgut. Later the parasites elongated and migrated forward, establishing a massive infection in the cardia, where broad, dividing forms were packed behind the stomodeal valve; many were attached to its cuticular surface by flagellar modifications called hemidesmosomes. Once this point in the life cycle of the parasite was reached, most promastigotes ceased dividing and became shorter and highly active. These metacyclic forms appeared first in the region of the cardia and stomodeal valve, then spread anteriorly to the pharynx, cibarium, and proboscis, as well as posteriorly to the midgut and hindgut.