When fifth instar larvae of the tobacco hornworm, Manduca sexta, were infected in vivo with pathogenic bacteria (Photorhabdus luminescens) or fungi (Beauveria bassiana), after a delay, hemolymph cell monolayers contained a new type of hemocyte not seen in uninfected insects. The cells were characterised by their huge size (up to 150 micrometers across) when spread on a glass coverslip. These cells are recognisable by their distinctive appearance even before spreading, but the cells spread extremely rapidly (reaching full size in less than 30 min)when allowed to settle, even after washing free of plasma. The same cell type was induced, again after a delay, by injecting microbial cell wall components into healthy larvae, indicating that this is an active response of the insect. Wounding, on the other hand, does not induce the appearance of these cells. In infected larvae, the novel hemocytes completely disappear once there is visible evidence that the microbial pathogen is proliferating in the host.
Species 1: Lepidoptera Sphingidae Manduca sexta (tobacco hornworm)
Keywords: immune response
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA