Nutrition & Dietary Needs Flashcards

Which carbohydrate is the structural component of the insect cuticle and is therefore a dietary requirement for growth and molting?

Answer: Chitin

Chitin, a polymer of N-acetylglucosamine, is the primary structural polysaccharide in the insect cuticle and must be synthesized from dietary nitrogen and glucose.

The primary circulating sugar in insect hemolymph, used for rapid energy mobilization, is:

Answer: Trehalose

Trehalose, a disaccharide, is the predominant blood sugar in most insects and is synthesized in the fat body from glycogen for rapid energy delivery.

Which of the following plant secondary metabolites can serve as a feeding stimulant (phagostimulant) for specialist herbivores adapted to that host?

Answer: Glucosinolates for cabbage loopers

Glucosinolates, which deter generalist herbivores, act as phagostimulants for specialist crucifer feeders like some caterpillar species adapted to Brassica plants.

Mycetocyte-harbored endosymbionts in aphids primarily supply which nutritional resource lacking in phloem sap?

Answer: Essential amino acids

Buchnera aphidicola, housed in specialized mycetocytes, synthesizes essential amino acids that are deficient in the aphid's phloem sap diet.

Insects that exhibit 'protein leverage' will increase overall food intake primarily when diet:

Answer: Is low in protein relative to carbohydrates

Protein leverage hypothesis states that insects (and other animals) overeat carbohydrates and total calories to reach their protein intake target when dietary protein concentration is low.

Which type of mouthpart is best suited for extracting liquid nutrition from plant or animal hosts without causing extensive tissue damage?

Answer: Piercing-sucking mouthparts

Piercing-sucking mouthparts, found in aphids, mosquitoes, and true bugs, allow penetration of host tissue to extract phloem sap, blood, or cell contents with minimal disruption.

Why is dietary cholesterol or plant sterols (e.g., sitosterol) essential for insects?

Answer: Insects use sterols for cell membrane synthesis and as ecdysteroid precursors since they cannot synthesize sterols de novo

Insects lack the enzymes to synthesize sterols from acetate, so dietary sterols are essential for membrane integrity and as precursors to the molting hormone ecdysone.