The effect of diet quality on delta C-13 and delta N-15 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/depl etions of N-15 and C-13 within body tissues are influenced by diet. The mai ze contained less hexose sugars and protein per gram than wheat. The isotopic spacing between the food and the whole insect was found to dif fer 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 d epletion in chitin relative to diet. The results for both delta(15)N and de lta(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in d elta(15)N and delta(13)C within organisms.