Parasitism by Cotesia plutellae inhibits imaginal wing disc development of diamondback moth, Plutella xylostella

Cotesia plutellae is an endoparasitoid that parasitizes the diamondback moth Plutella xylostella. Parasitized P. xylostella exhibits immunosuppression and developmental retardation, resulting in death before pupation after parasitoid emergence. Except digestive organ, most host internal organs of parasitized P. xylostella show poor development, suggesting nutrient deprivation by the parasitoid. Here we report another significant morphological aberration in the development of parasitized P. xylostella. Imaginal wing disc development was markedly inhibited, while nonparasitized larvae developed two pairs of wing discs (approximately 0.5 mm diameter) in the thorax at their final instar. Since P. xylostella wing disk development can begin at the late larval stage depending on their nutritional status, C. plutellae parasitism may prevent wing disc development indirectly by disrupting host nutrient usage. Also, the hypotrophied wing disc of parasitized P. xylostella may be associated with immunosuppression due to its structural association with the hematopoietic organ in most lepidopteran wing discs. This study showed a high correlation between wing disc development and total hemocyte population in P. xylostella.