Body size and cell size in Drosophila: the developmental response to temperature

In Drosophila, like most ectotherms, development at low temperature reduces growth rate but increases final adult size. Cultures were shifted from 25 degrees C to low (16.5 degrees C) or to high (29 degrees C) temperature at regular intervals through larval and pupal stages, and the flies of both se xes showed an increase or decrease, respectively, in the size of thorax, wi ng and abdominal tergite. Size changes in the wing blade resulted from chan ges in the size of the epidermal cells (with only a small increase in cell number in males reared at low temperature). The temperature-shifts became l ess effective as they were made at successively later developmental stages, demonstrating a cumulative effect of temperature on adult size. The thorax and wing develop From the same imaginal disc, with most cell division occu rring in larval stages, but they differ in timing of temperature sensitivit y, which extends only to pupariation or into the late pupal stage, respecti vely. Growth of the adult abdomen occurs largely after pupariation but its size is temperature-sensitive through both larval and pupal stages. We disc uss growth control in Drosophila and the likely effects of temperature on f ood assimilation, growth efficiency and allocation of nutrients to the prod uction of different tissues. (C) 1998 Elsevier Science Ltd. All rights rese rved.