Frequency response characteristics of isolated retinas from hatchling leatherback (Dermochelys coriacea L.) and loggerhead (Caretta caretta L.) sea turtles.

Electroretinographic recordings were made from hatchling loggerhead and leatherback sea turtle eyecup preparations during presentation of sinusoidally modulated lights of different frequencies, mean intensities and colors. Cross-correlation analysis was performed to determine the extent to which the responses followed the intensity modulated light sources. For both species mean light intensity had no significant effect on the frequency modulated responses over a 1.5 log unit range of intensities. Both species showed the best following to blue light and the poorest tracking to red light. Leatherback retinas did not follow frequencies above 10 Hz, while loggerhead responses extended out to 15 Hz. These visual low pass filter characteristics are consistent with attributes of the visual ecology of each species, as well as with the latencies and slow rise times exhibited by these retinas to brief flashes of light.