Foraging by Drosophila melanogaster Larvae in a Patchy Environment
The food resources of Drosophila comprise decaying vegetable matter distributed in patches, yet foraging behavior has not been examined in larvae reared continuously in a patchy environment. Here, the extent and rate of inter-patch movement was studied in larvae of four wild strains of D. melanogaster inhabiting an experimental arena from the egg stage to the third larval instar. The hypotheses were that larvae would forage primarily in the third instar, that larvae would move from low-protein patches at higher rates than from high-protein patches, and that foraging rates would be higher on an agar substrate than on sand. Larvae hatching on a nutrient-poor food patch switched to a nutrient-rich patch during the first instar. The rate of interpatch switching increased with larval age, as did the number of larvae roving on the substrate between food patches. Inter-patch distance affected switching speed---the closer the patches, the faster the switching. High protein patches were preferred over low-protein patches, but there was a bias towards staying on the natal patch. Significant variation among strains in latency to forage, in proportion of larvae that switched patches, and in the rate of roving between patches suggests that there is natural genetic variation for these traits. Larvae switched food patches on a substrate of moist sand as quickly as on an agar substrate.
KeywordsLarval foraging patchy resources roving larvae Drosophila
Thanks to Prof. Danny Segal for chemicals and for receiving fly shipments, and to Prof. Charlambylos Kyriacou for many wild strains, two of which were chosen for this study. The Canton-S strain was obtained from the Bloomington Drosophila Stock Center (NIH P40OD018537). Tzviel Frostig helped with the preparation of figures and gave me much valuable instruction in r programming.
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