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First published online February 4, 2005
Journal of Experimental Biology 208, 611-623 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01404

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Nutrition interacts with parasitism to influence growth and physiology of the insect Manduca sexta L.

S. N. Thompson^*, R. A. Redak and L.-W. Wang

Department of Entomology, University of California, Riverside, California 92521, USA

View larger version (23K): [in a new window]   Fig. 1. Two-dimensional representation of nutrient intake by normal unparasitized M. sexta larvae (filled circles), and larvae parasitized by C. congregata (open circles), maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose. Dotted lines are nutrient rails representing the trajectory of nutrient intake expected for larvae feeding on the individual diets. Nutrient intake points indicate actual nutrient intake (± S.E.M.). Significant differences (P<0.05) in nutrient intake between normal and parasitized larvae on the same diet are indicated by an asterisk. The lines through individual intake points for normal and parasitized larvae are the intake arrays. Development times for each dietary nutrient ratio are shown in parentheses. Dietary nutrient ratios are shown relative to the level of each nutrient (C, casein; S, sucrose) in the basal chemically defined formulation where 1.0=90 g l-1.

View larger version (18K): [in a new window]   Fig. 2. Effects of dietary nutrient ratio and parasitism by C. congregata on growth (mass gain) of M. sexta larvae maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose. Bars show means ± S.E.M. Significant differences (P<0.05) among normal larvae are indicated by different lowercase letters and among parasitized larvae (including parasite biomass) by different upper case letters. Significant differences between normal and parasitized (including parasite biomass) larvae on the same diet are indicated by an asterisk. Dietary nutrient ratios are shown relative to the level of each nutrient (C, casein; S, sucrose) in the basal chemically defined formulation where 1.0=90 g l-1.

View larger version (19K): [in a new window]   Fig. 3. Effects of dietary nutrient ratio and parasitism by C. congregata on growth (mass gain) of M. sexta larvae maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose, after accounting for differences in protein and carbohydrate intake between diets. Bars show least-square means ± S.E.M. Differences between diets and between normal and parasitized larvae are due to differences in utilization efficiency. Significant differences (P<0.05) among normal larvae are indicated by different lowercase letters and among parasitized larvae (including parasite biomass) by different upper case letters. Significant differences between normal and parasitized (including parasite biomass) larvae on the same diet are indicated by an asterisk. Dietary nutrient ratios are shown relative to the level of each nutrient (C, casein; S, sucrose) in the basal chemically defined formulation where 1.0=90 g l-1.

View larger version (51K): [in a new window]   Fig. 4. Multi-dimensional profiles illustrating the effects of nutrient consumption on growth (mass gain) by normal unparasitized M. sexta larvae and larvae parasitized by C. congregata, maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose. (A,C) Three-dimensional models for normal and parasitized larvae. (A) Normal: F=49.04, P<0.0001, r2=0.9491; (B) parasitized: F=148.38, P<0.0001, r2=0.9624. (B,D). Contour maps for normal and parasitized larvae, respectively. Nutrient rails shown for the individual diets. Actual mass gain by individual larvae indicated by filled circles.

View larger version (15K): [in a new window]   Fig. 5. Effects of dietary nutrient ratio and parasitism by C. congregata on blood concentration (mg ml-1) of (A) protein, (B) free amino acids and (C) trehalose in fifth instar M. sexta larvae maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose. Bars show means ± S.E.M. Significant differences (P<0.05) among diets between normal larvae are indicated by different lowercase letters, and between parasitized larvae (including parasite biomass) by different uppercase letters. Significant differences between normal and parasitized (including parasite biomass) larvae on the same diet are indicated by an asterisk. Dietary nutrient ratios are shown relative to the level of each nutrient (C, casein; S, sucrose) in the basal chemically defined formulation, where 1.0=90 g l-1.

View larger version (17K): [in a new window]

View larger version (52K): [in a new window]   Fig. 6. Contour maps illustrating the effects of nutrient consumption on blood protein, free amino acids and trehalose concentrations (mg ml-1) during the fifth stadium of normal unparasitized fifth instar M. sexta larvae and larvae parasitized by C. congregata, maintained over the fourth and fifth stadia on a chemically defined artificial diet having varying ratios of casein and sucrose. (A,D) Protein, (B,E) free amino acid and (C,F) trehalose concentrations of (A-C) normal unparasitized larvae and (D-F) parasitized larvae.