Effects of high dietary lipid on larval growth and mortality rates of Manduca sexta, the tobacco hornworm


Meeting Abstract

P3.65  Thursday, Jan. 6  Effects of high dietary lipid on larval growth and mortality rates of Manduca sexta, the tobacco hornworm VERWORN, N.R.*; GREENLEE, K.J.; North Dakota State University Natalie.Verworn@ndsu.edu

Excess fat storage has fitness costs for many organisms. Plutella xylostella caterpillars fed high carbohydrate diets over generations avoided excess fat storage, suggesting metabolic adaptations. However, dragonflies infected with gut parasites can exhibit increased fat storage and a suite of traits that resemble those found in metabolic syndrome. Thus, insects may be useful models for understanding aspects of fat storage and metabolism. However, the effects of increased dietary lipid have not been as thoroughly investigated. Manduca sexta caterpillars fed high-fat diets during the 4th instar had slower growth and increased fat storage. Yet, it is unclear whether this resulted in adverse health consequences. To test this hypothesis, we first developed high and moderate-fat diets. We compared caterpillar growth on these diets to that on the standard diet for M. sexta. Caterpillars reared on moderate-fat diet (3.4% lipid) showed a 34% increase in total mass at day 21, compared to those on standard diet (0.4% lipid). In contrast, M. sexta reared on a high-fat diet (5.6% lipid) were 43% smaller at day 21 and had an 80% mortality rate after 28 days of growth. Moderate-fat and control diets resulted in no mortality. Lipid analysis of caterpillars will be used to determine the basis for the increase in body size. Changes in gene expression are likely to occur when we observe changes in growth rates. Likely candidates include lipid transport genes and genes involved in growth and tissue remodeling. This work was supported by NSF EPSCOR EPS-0447679, NIH NCRR- 2P20 RR015566, and NSF IOS-0953297 to KJG.

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