How well do specialist feeders regulate nutrient intake? Evidence from a gregarious tree-feeding caterpillar

Abstract

SUMMARY Nutritional regulation is a powerful mechanism used by generalist feeders to obtain the balance of nutrients they require from nutritionally diverse,perhaps unbalanced, foods. We examined nutritional regulation in a species with a narrow individual diet breadth: the forest tent caterpillar, Malacosoma disstria. Fourth instar caterpillars were provided with artificial foods consisting of different ratios of protein to digestible carbohydrate in no-choice, choice and compensatory feeding experiments. In the no-choice test, caterpillars were confined to a single food source of varying protein/carbohydrate ratio for the duration of the fourth larval stadium. Caterpillars performed best on equal-ratio and slightly protein-biased diets. Significant reductions in performance were only observed on extremely protein-or carbohydrate-biased diets. Daily consumption of the three acceptable intermediate diets was consistent with volumetric regulation, but the timing of the moult to the next instar appeared linked instead to protein intake. In the choice test, caterpillars were provided with two complementary foods, one biased toward protein and the other toward carbohydrate, for the duration of the stadium. The caterpillars fed randomly from the two food sources presented to them, except for the extremely protein-biased diet (P:C ratio of 35:7),which they avoided. The compensatory feeding experiment tested whether forest tent caterpillars deprived of either protein or digestible carbohydrate would select a food containing the deficient nutrient. Insects were conditioned on either protein-only, carbohydrate-only, protein-and-carbohydrate or no-nutrient foods, then offered a choice between protein-only and carbohydrate-only foods. Unlike previously studied generalist feeders, our caterpillars did not compensate for protein deficiency and showed only very weak evidence of compensation for carbohydrate deficiency. Forest tent caterpillars are colonial trail-laying forest folivores that are generally confined to a single host plant and hence do not experience much diversity in food nutrient ratios. We show that forest tent caterpillars do not independently regulate protein and carbohydrate intake. These findings are consistent with predictions that nutritional regulation abilities should be less important in animals with narrower diet breadths.

Anthropogenic changes in sodium affect neural and muscle development in butterflies

“…Thus, it is possible that more extreme road salt runoff (e.g., along interstates) could result in more negative impacts on herbivores feeding alongside the road. Although caterpillars may sometimes be able to move away from host plants with toxic sodium levels and choose more nutritious host plants (57), their ability to disperse and make adaptive diet choices is likely quite limited (44,45,58,59). Studies on the movement and food preferences of caterpillars will be necessary to determine the extent to which corridors of roadside plants with very high sodium levels may negatively affect caterpillar survival.…”

Functional Analysis of the Kunitz Trypsin Inhibitor Family in Poplar Reveals Biochemical Diversity and Multiplicity in Defense against Herbivores

“…BAW (Mamestra configurata) extracts were obtained from Dr. Dwayne Hegedus (Agriculture and Agri-Food Canada). Dr. Emma Despland (Concordia University) provided FTC (Malacosoma disstria) midguts dissected from fourth and fifth instar larvae that were reared on artificial diets (Despland and Noseworthy, 2006). FTC midguts were extracted into insect Ringer's solution and clarified by centrifugation, as described previously (Hegedus et al, 2003).…”

Larval nutrition affects life history traits in a capital breeding moth

“…Nonetheless, these mechanisms are not perfect and caterpillars on unbalanced diets generally exhibit lower survival (Despland and Noseworthy, 2006;Merkx-Jacques et al, 2008) (Lee et al, 2002) and altered biochemical composition of the pupa (Lee et al, 2002;Lee et al, 2003;Lee et al, 2004). However, it is not clear how variations in nutrient intake influence allocation to various fitness functions (Boggs, 2003).…”

“…Previous work has established that forest tent caterpillars are not efficient at pre-ingestively regulating nutrient intake (Despland and Noseworthy, 2006). Food protein-to-carbohydrate ratio affects larval performance, which is best on an equal protein-tocarbohydrate ratio or on slightly protein-biased diets.…”