A creature known as "the scavenger of the deep" has surprised its keepers at an aquarium by "fasting" for more than four years.

The giant male isopod, called No. 1 to distinguish it from the two other giant isopods kept at Toba Aquarium in Mie Prefecture, last ate in January 2009, when it was fed a whole horse mackerel.

The isopod devoured the fish, bones and all, in just five minutes. But it has not eaten anything since, with Feb. 10 marking 1,500 days without food.