science

VISION

Human vision

In the human retina, there are two types of photoreceptor cells, rods and cones, responsible for brightness and color visions, respectively.
Rhodopsin is the visual pigment in rhod cells and exists as a complex of retinal and opsin (polypeptide chain). The optical absorption spectrum of rhodopsin is about 500 nm (green visible light) so that it efficiently detect sun light on the Earth’s surface.
There are three types of cone cells, (blue, green, and red). They also use retinal proteins to detect light, but the amino acid sequences of blue, green, and red opsin proteins are different to each other, leading to different optical absorption peaks of them.

Fish vision

In contrast to terrestrial animals, fish experience different photic environment depending on the depth of the ocean where they live. For instance, red light does not reach deep ocean where the distribution of light exhibits narrow peak around 480 nm, and deep sea fish that are red are not visible from predators.
Japanese eel spawns in the deep sea, the young adults migrate into freshwater, and the mature fish return to the deep sea for reproduction. For their dim-light vision, young and adult eels use EEL-A and ELL-B, respectively. The optical absorption maximum (lambda_max) of EEL-A (500nm) reflects the shallow freshwater environment, whereas those of EEL-B (480-485 nm) match with their photic envirionments in the deap sea.

Snake vision

It is wellknown that the pit organs of rattlesnakes are infrared pinhole cameras of very poor optical quality. However, this sounds paradoxical because these snakes demonstrate outstnding skills as night hunters. van Hemmem and colleagues used neural network model to explain the surprisingly good infrared vision of snakes [4-6].

science

VISION

Human vision

Fish vision

Snake vision

References