Meeting Abstract

71.4  Jan. 7  The developmental mechanism and evolution of allometry in Drosophila SHINGLETON, A.W.; Michigan State University shingle9@msu.edu

The developmental mechanisms that control the relationship between final body size and organ size in animals are virtually unknown. This relationship, called static allometry, arises because variation in adult body size is accompanied by corresponding variation in organ size. Here we examine the static allometries created by rearing Drosophila under different environmental conditions. The male genitals show a hypoallometric relationship with body size when size variation is a consequence of variation in developmental nutrition, but a different allometric relationship when size variation is a consequence of variation in rearing temperature. Different sources of variation may therefore create different allometric relationship using different developmental mechanisms. We show that one such mechanism is likely to involve the insulin-signaling pathway, which is known to regulate growth with respect to nutrition in Drosophila, and most animals. Suppression of the insulin receptor has less of an effect on the size of the male genitals than it does on other organs. This and additional genetic data suggest that the �nutritional hypoallometry� of the male genitals is explained by differential activity of insulin-pathway genes in the genitals relative to other body parts. Organ-specific regulation of the insulin-signaling pathway may therefore be a general method by which animals regulate nutritional static allometries, and suggests a potential mechanism by which allometries can evolve.