Histopathology of Aedes aegypti (Diptera: Culicidae) larvae parasitized by Reesimermis nielseni (Nematoda: Mermithidae)

Histological observations were made on larvae of Aedes aegypti (L.) parasitised for 2, 4 or 6 days by Reesimermis nielseni. Little difference was detected between the tissues of uninfected and parasitised larvae 4 days after infection, at which time most hosts were in the early fourth instar and their fat-bodies were well developed. The nematodes grew most rapidly between day 4 and day 6 following infection, depleting host metabolites, reducing the size of the fat-body and other host storage tissues while accumulating storage material in their trophosomes. The development of host imaginal discs was inhibited during this period. The severity of the effect on the host tissues depended on the intensity of infection. Dry-weight measurements of nematode and host supported the histological observations showing that the nematode developed most rapidly 4-6 days post-infection, thus causing the most serious effects upon the host at that time.ADDITIONAL ABSTRACT:Histological observations were made of Aedes aegypti larvae parasitized for 2, 4, and 6 days by Reesimermis nielseni. Little difference was detected between the tissues of uninfected and nematode-parasitized larvae 4 days after infection, at which time most hosts were in the early fourth instar and their fat bodies were well developed containing abundant storage materials. Nematodes grew most rapidly between days 4 and 6 of parasitism, depleting host metabolites, reducing the fat body and other host storage tissues while accumulating storage material in their trophosomes. Development of host imaginal discs was inhibited during this period. The severity of the nematodes effect on host tissues depended upon intensity of infection..