Transition of the retinal area centralis in bluegill Lepomis macrochirus as an implication of changes in feeding ecology with age

Abstract

In teleosts, the area of peak ganglion cell density in the retina (area centralis, AC) is thought to reflect the primary visual axis for feeding. The bluegill Lepomis macrochirus are known to undergo ontogenetic shifts in diet preference, but because their diet is affected by population density, interspecific competition, and seasonal changes in prey availability, they are considered generalist predators. We investigated whether the diet shifts of the bluegill were associated with a change in the location of the AC (total length of fish specimens, range 44–243 mm). The AC was located temporally in the retina of smaller fish (40–100 mm), and the area of increased density included the ventral and central regions of the retina. Conversely, the AC was located in the dorso-temporal region of the retina in larger (100–200 mm) fish. Lastly, in the largest bluegill (> 200 mm), the AC was located in the temporal region of the retina. In all cases, the orientation of the visual axis was consistent with the known diet preferences of the different size classes.