European Mole - Vision

Vision

Due to the subterranean nature of this mole, there is an anatomical regression of its eyes at several organizational levels. Its eye has a diameter of only 1mm and is buried beneath fur and has a cellular lens. The organization of the retina is quite similar to that of a typical mammal. It has been determined that there are about 2000 ganglion cells and the optic nerve is roughly 50 μm with 3000 axons. Roughly 15% of these axons are mylinated. The photoreceptors are not the normal rod-like or cone-like shape that you would expect to see. Instead they all have one uniform shape with three distinct features:

1) The receptors are short along the radial axis

2)The inner and outer segments are similar in length

3)The outer segments appear to be significantly degenerated

Studies have shown that T.europaea does have photopic vision, contrary to popular belief that all moles are blind. Two cone opsins have been found in the eyes of T. europaea but their function is still under investigation. In a study of the mole eyes it was found that Talpa withdraws when exposed to a flashlight and can also perform light/dark discrimination tasks. The cone cells in the eye are unlikely to provide high-resolution vision but they could allow a detection of movement and some hue discrimination. It is suggested that in subterranean mammals vision is used to detect predators that have broken into the tunnels.