* Japanese name: Hario
* Scientific name: Gasterosteus aculeatus leiurus
* Description: Small, perky fish, as adults sticklebacks are typically between 6- and 10-cm long. They have 30 to 40 lateral armor plates along their sides, and also three long dorsal spines that can be raised.
* Where to find them: In cool, clear freshwater lakes, ponds and streams, from Hokkaido to Honshu.
* Food: Plankton and insect larvae, also water fleas, worms, snails, sometimes fish eggs and occasionally algae. Despite the three protective spines, many other fish eat sticklebacks, as do many water birds.
* Special features: The stickleback has a special place in the hearts of both school children and zoologists. The archetypal fish kept in a jar by generations of children, the stickleback is also a model organism in the study of animal behavior. Males build nests on the riverbed or bottom of a pond, and defend them. During the courtship season, the males develop a red chin and belly, a signal which acts as both a challenge to other males, and a mating beacon to females full of eggs and ready to mate. The fish produce the red pigment from carotenoids in their food, so a male that is brighter red that others is probably one that has been successful in foraging. Hence the signal informs rival males on the likely strength of their opponent, and to females of the quality of their potential mates. The strength of the male is important not just for their genes: Once the female has laid her eggs in the nest, the stickleback male defends them, and fans water across the eggs, ensuring they receive a good supply of oxygen. Sticklebacks have four color photoreceptors in their eyes, one more than we have. This means they can see the three colors we can see, plus light in ultraviolet wavelengths. As if all that weren’t enough, the stickleback has also had its genome sequenced.



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