A receptor cell can respond to a single molecule of the pheromone called bombykol and 200 molecules can cause a behavioral response. Octopus Retina contains 20 million photoreceptors. The pupil of the eye is rectangular. By tasting this way, an octopus does not have to leave the safety of its home. Penguin Has a flat cornea that allows for clear vision underwater.
Penguins can also see into the ultraviolet range of the electromagnetic spectrum.
Pig Tongue contains 15,000 taste buds. For comparison, the human tongue has 9,000 taste buds. Can detect sounds as low as 0.1 Hz. Platypus Has electric sensors in its bill that can detect 0.05 microvolts. Other receptors in the bill are for touch and temperature detection.