Dawn of vision – And why blue light might be so special
Virtually all mammalian species exhibit some kind of circadian rhythm that affects their activities. These rhythms parallel the cycle of day and night and are, thus, in most cases linked to the perception of light. However, major surprises were in store for scientists, when they investigated whether mutant mice, lacking the well known image-forming rod and cone cells in their retinas, still possessed a circadian rhythm. —>—>
We see them, but do animals see united colours of Benham’s disc too?
I heard of a man who worked as a magician after World War II and in his performances used a disc with a strange pattern of black and white lines. However, when turned around and spun at high speed, the disc’s black and white pattern created the impression of faint reddish or orange, even greenish or yellowish colours in human observers. —>—>
Fish without eyes
It is sometimes quite shocking what some people think the work of an animal biologist consists of. One day, when visitors to our house took a look at my aquarium and admired the fish in it, my ears had to hear the following comment: “Very interesting, but doesn’t it hurt them when you remove their eyes?” “What do you think?”, came my reply, “they are blind fish. They never have any eyes! They are Mexican cave fish, Astyanax mexicanus.” Stupid visitors (I did not say that), but they obviously did not know that some species of fish are naturally eyeless.