Ocular surface reflex in pseudocelli.
Light, when striking the ocular surface of terrestrial animals, is partially reflected by the lacrimal film, which can be seen as a bright spot on the cornea. This reflection, termed "the corneal reflex," should actually be called the "lacrimal film reflex," as it is reflected mainly by the lacrimal film. An isolated corneal reflex exists only in aquatic animals, which have no lacrimal film, and in abnormal conditions in terrestrial animals, e.g., when their corneas become dry. Some animals are able to mimic and reproduce the external appearance of the eyes of other species for defensive display purposes. In these eye-spots or pseudocelli, the ocular surface reflex is present as an important physiognomic feature in terrestrial animals. However, we have observed that it is absent in aquatic animals. We hypothesize that the corneal reflex of aquatic animals is very weak and inconspicuous due to the small difference of refractive index between water and cornea, and for this reason is not a physiognomic characteristic of their eyes. Thus, pseudocelli present on sub-aquatic animals do not display an ocular surface reflex.
Murube
Juan
J
University of Alcala-Madrid, Spain.