ORGAN AND CELL ALLOMETRY IN HAWAIIAN DROSOPHILA - HOW TO MAKE A BIG FLY

The importance of body size in predicting many aspects of an animal's biology has become well established in recent years. However, little i s known about how body size evolves at the cellular level. Some publis hed data suggest that it is cell number and not cell size that accompa nies changes in organ and body size across taxa. We examined organ and cell allometry in the wing, eye and basitarsus of adult Hawaiian Dros ophila, ranging in body length from 0.2 mm to 0.8 mm. Linear measureme nts of all three structures exhibit a positive allometry with body len gth. Exponents of the allometric equation were 0.96, 0.55 and 1.50 for wing, eye and basitarsus, respectively. Surface markers were used to quantify cell size of each organ. The allometric exponents for cell si ze as a function of organ size were 0.53, 0.68 and 0.33 for wing, eye and basitarsus, respectively. In contrast to reports in the literature on other systems, our results for Hawaiian Drosophila indicate that c ell size may contribute between one third and two thirds to evolutiona ry changes in organ and body size.