The effect of diet quality on δ13C and δ15N in the tissues of locusts, Locusta migratoria L.

Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C-3) or maize (C-4), to determine whether relative enrichments/depletions of N-15 and C-13 within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat. The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1 parts per thousand enrichment in delta(15)N compared to + 2.8 parts per thousand for wheat, possibly due to increased fractionation due to protein recycling. The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both delta(15)N and delta(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in delta(15)N and delta(13)C within organisms.