DOES AGE MATTER IN STUDYING THE CRUSTACEAN EYE

Fifty randomly selected publications dealing with aspects of crustacea n vision had their Materials and methods sections examined. In half of the articles gleaned, only the name of the animal under study was giv en; the other half mentioned ''adult'' or ''mature'' animals; twelve p apers provided information on size or age of the experimental animal a nd six gave the sex. In Petrolisthes elongatus, rhabdom microvilli not only become more regular in outline as the animal grows, but also dec rease in diameter from 90.4 +/- 21.2 nm in crabs of 5.0-8.9 mm carapac e length via 86.6 +/- 13 nm in crabs of 9.0-12.9 mm carapace length to 79.7 +/- 7 nm in crabs of 13.0-16.9 mm carapace length. Approximately 400 cross sectional diameters of microvilli from identical regions in four eyes of each size class were measured and provided the basis for Anova-, Levene-, and t-tests. The three size classes possess microvil li of significantly different diameters and standard deviations. Our o bservations show that investigators of the crustacean photoreceptor ha ve frequently neglected to consider the size of their experimental ani mals, but that this practice should not be continued as the now docume nted changes in microvillus diameters may influence the amount of visu al pigment present and, thus, the photoreceptor's sensitivity to light .