Learning Smart

in video above, some creatures eat the fish carcasses wildly in a few second. The remain is just a fish bone. It makes many natives scary. After reaserch, the reasercher have proved that creatures are not dangerous for human. evidently, that creatures is cirolana (latin name). In the reaserch, about 500 cirolanas are placed in an aquarium. then, someone sink his finger to that place. but, the result is cirolanas become scared, even they feigned death.
Cirolanas have a big role in food chain. They are eated by bigger fish in the sea. after the reaserch put a fish in the same aquarium, they are eaten by that fish.

Coastal hermit crabs live in snail shells. As snail shells are not part of the hermit crab's body, they do not grow following the growth of the hermit crab inside. Hermit crabs should obtain appropriate-size shells as they grow. The optimal shell size decreases as the size of the hermit crab decreases. For example, the optimal-size shell for a crab of 5 mm in carapace length is 14 mm in shell width. Shells deviating from this size are unsuitable for this crab. Larger shells are heavy and difficult to carry, and in smaller shells crabs cannot completely conceal the body.

A hermit crab sometimes attacks another crab to obtain a new shell. In this attempt, an attacker crab that succeeds in evicting the other should discard its original shell and move into the newly obtained shell. As a result, the attacked crab moves into the shell discarded by the attacker crab. Thus, fights by hermit crabs for shells assume a form of exchange. When a crab obtains a new shell whose size is nearer to the optimal value than the original, the crab can be regarded as gaining, but when the new one further deviates from the optimal than the original, it can be regarded as losing.