Meeting Abstract

P3.132  Sunday, Jan. 6  Hormonal Control of Developmental Effects on Immunity in the Caterpillar, Manduca sexta BOOTH, KK*; GREENLEE, KJ; North Dakota State University ; North Dakota State University kimberly.booth@my.ndsu.edu

Insect immunity is innate immunity and can be classified as humoral, such as the production of anti-microbial peptides (AMPs) and phenoloxidase (PO), or cell-mediated. Cell-mediated immunity includes encapsulation, nodulation, and phagocytosis. Previous research has shown that insect immune responses change within an instar, or developmental stage. Manduca sexta larvae (tobacco hornworm) early in the 5th and final instar have more robust cell-mediated and humoral immune responses to bacterial infections when compared to animals later within that instar. However, it is unclear how immunity varies within other instars. Before we can compare the immune response in 3rd and 4th instars, we validated the effect of development on immunity in 5th instar M. sexta. AMP and PO activity of hemolymph from M. sexta did not vary within the first four days of the 5th instar. However, hemolymph from M. sexta injected with vehicle had statistically higher levels of PO activity compared to caterpillars injected with Micrococcus lysodeikticus regardless of age, indicating that bacterial injection depletes PO stores. Other research has shown that juvenile hormone (JH), which regulates development and peaks at the beginning of an instar, may be immunostimulatory. To test the hypothesis that JH drives developmental-dependent changes in immunity, we will apply JH inhibitor to caterpillars early in the 5th instar and JH analog in late 5th instar caterpillars, and measure AMP and PO activity as an index of immune function. These data highlight the need for accounting for within-instar age in experimental design.