Fig. 3. Mitochondrial luminosity of anal papillae (AP) of animals reared in acidic (pH 4), neutral or alkaline (pH 11) media. All measurements were made with an exposure time of 1/8 s and at the same magnification. Luminosity was determined for the base, midsection and tip of one AP from each animal. Luminosity was always greatest in proximal and distal regions, and lowest in the central region. Larvae reared in acidic media (RS 4) showed reduced mitochondrial densities in the midsection and tip, and mitochondrial densities averaged across regions were also reduced in RS 4 (P<0.05).