Immune Defense Varies within an Instar in the Tobacco Hornworm, Manduca sexta.
Research on how insect immunity changes with age as insects develop within an instar, or larval developmental stage, is limited and contradictory. Insects within an instar are preparing for the next developmental stage, which may involve changes in morphology or habitat. Immunity may also vary accordingly. To determine how immunity varies in the fifth instar, we tested humoral immune responses, antimicrobial peptide activity, and phenoloxidase activity using the tobacco hornworm, Manduca sexta. We determined that while M. sexta have more robust antimicrobial peptide and phenoloxidase responses at the beginning of their fifth instar, this did not translate into better survival of bacterial infection or lower bacterial load in the hemolymph. We also determined that M. sexta injected with bacteria early in the fifth instar experience lower growth rates and longer development times than caterpillars of the same age injected with sham. This could indicate a shift in energy allocation from growth and development to metabolically costly immune responses. Because of the importance of insects as pests and pollinators, understanding how immunity varies throughout development is critical.
Department of Biological Sciences, North Dakota State University, Fargo, North Dakota 58102; 2Department of Arts and Sciences, Aurora University, Aurora, Illinois 60506; 3Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, North Dakota 58102.
Kimberly
K
Booth
Lizzette
L
Cambron
Nathan
N
Fisher
Kendra J
KJ
Greenlee
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000276:immunology; D004926:Escherichia coli / Q000502:physiology; D006458:Hemolymph / Q000276:immunology / Q000382:microbiology; D007814:Larva / Q000276:immunology / Q000382:microbiology; D018402:Manduca / Q000276:immunology* / Q000382:microbiology; D014442:Monophenol Monooxygenase / Q000276:immunology; D020615:Stenotrophomonas maltophilia / Q000472:pathogenicity
D023181:Antimicrobial Cationic Peptides; D014442:Monophenol Monooxygenase