A correlation between macronutrient balancing and insect host-plant range: evidence from the specialist caterpillar Spodoptera exempta (Walker).
In an earlier study, we showed that the ingestive responses of the generalist caterpillar Spodoptera littoralis to foods imbalanced in their protein:carbohydrate content is similar to generalist locusts, but differs from that of specialist-feeding locusts. Here we further pursued the comparison by repeating the experiments using a closely related specialist caterpillar, Spodoptera exempta. First, caterpillars were allowed to self-compose a diet of preferred protein:carbohydrate balance by mixing between nutritionally complementary foods. Then, they were confined to one of five imbalanced foods, in which we measured the trade-off between over- and under-ingesting the two nutrients. On complementary foods, the caterpillars actively regulated their protein and carbohydrate intake. In the no-choice experiment, those fed excess-protein foods ingested small surpluses of protein compared with generalist feeders, thus showing a pattern of nutrient balancing similar to that observed in specialist locusts. Utilisation data indicated that ingested excesses and deficits were to some extent offset by differential utilisation. Evidence also showed that post-ingestive responses of the specialist S. exempta were less flexible than those observed in the generalist S. littoralis, a pattern which is again in accordance with comparisons of acridids differing in their host-plant range.
Lee
Kwang Pum
KP
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK. kwang.lee@zoo.ox.ac.uk
Raubenheimer
David
D
Behmer
Spencer T
ST
Simpson
Stephen J
SJ
D000818:Animals; D001823:Body Composition; D001835:Body Weight; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005247:Feeding Behavior / Q000502:physiology; D005518:Food Preferences / Q000502:physiology; D006790:Host-Parasite Interactions; D008055:Lipids / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010944:Plants / Q000469:parasitology*; D011679:Pupa / Q000378:metabolism; D013045:Species Specificity; D018411:Spodoptera / Q000378:metabolism / Q000502:physiology*; D013223:Statistics as Topic / Q000379:methods
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D008055:Lipids; D009584:Nitrogen