Lankesteria barretti n. sp. (Eugregarinida,Diplocystidae), a Parasite of the Mosquito Aedes triseriatus (Say) and a Review of the Genus Lankesteria Mingazzini*

SYNOPSIS. Lankesteria barretti n. sp. (Eugregarinida, Diplocystidae) is named from the mosquito Aedes triseriatus in Texas. The young cephalins occur within the midgut epithelial cells. When they reach a length of about 150–200 μ they rupture the host cell and are released into the space between the epithelium and the peritrophic membrane, becoming gamonts. These grow to about 140–310 by 40 μ at the anterior end and 12 μ at the posterior end. When the host pupates they enter the lumen of the Malpighian tubules; pairs join in syzygy by their anterior ends and later more laterally. Each pair forms a spherical gametocyst about 60–100 μ (exceptionally 250 μ) in diameter. A large number of oocysts develop in each gametocyst. The mature oocysts are spindle-shaped, 11 by 5.4–5.7 μ, and contain 8 elongate sporozoites and a refractile residuum. The gametocyst wall breaks down, releasing oocysts in the Malpighian tubules of the host when it is adult. The oocysts pass out in the feces and presumably infect new larvae by ingestion. The cephalins and gamonts of L. barretti differ from those of L. culicis (of Aedes aegypti) in having a relatively anterior instead of a central nucleus and in lacking a noticeable mucron; its longitudinal folds are not as well-developed as in L. culicis, and its paraglycogen granules are larger. The fine structure of L. culicis and L. barretti is described in detail. Their gamonts have a polar ring but no definite conoid. The taxonomy of the genus is reviewed, but its species have been so poorly described that it is impossible to be sure whether they are all really Lankesteria. About 19 species have been described (5 from turbellaria, 8 from tunicates, perhaps 1 from Amphioxus, 1 from the chaetognath Sagitta sp., 1 from Phlebotomus and 3 from mosquitoes).