An ultrastructural study of the invasion of Culex quinquefasciatus larvae by Leptolegnia chapmanii (Oomycetes: Saprolegniales).

Transmission electron microscopy of the invasion of Culex quinquefasciatus by Leptolegnia chapmanii confirmed that it is a primary pathogen and revealed several differences between penetration via the gut and penetration via the integument. The latter often involved aggregations of zoospores, appressoria-like swellings of the invasive hyphae, and lateral growth of hyphae between the epicutical and endocuticle. These features were not detected in the case of gut invasion, but hyphal septa at the point of entry were apparently peculiar to this route. There was no evident tissue specificity, and death presumably resulted from generalized destruction of tissues.