Deep sea creature at Japan aquarium has not eaten for 4 years

Tokyo, Feb 21 (Kyodo) A giant sea creature weighing over 1 kg and measuring 29 centimeters has surprised its keepers at an aquarium in western Japan 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 Japanese 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.
The crustacean also known as "a scavenger of the deep" was brought to the aquarium from the Gulf of Mexico in September 2007, measuring 29 centimeters and weighing 1 kilogram, and despite its lack of food still looks perfectly healthy, the keepers say.

"We have done all we possibly can," said Takeya Moritaki, who is responsible for the creature.
Moritaki said he has tried an assortment of feeds, including squid legs and saury, but the isopod has ignored them all.

Little is known about the biology of the creature, which lives in deep waters of the Gulf of Mexico and the Caribbean and which lives off dead animals and fish, and it remains a mystery why the isopod suddenly stopped eating and why it has remained healthy.
"Giant isopods are always in a state of semi-hibernation because they don't know when they can eat so they limit spending energy on breathing and other activities," said Taeko Kimura, a marine ecologist at Mie University.

"For that purpose they sometimes keep a large amount of fat in their livers, so maybe 'No 1' still has a source of energy in its body, and that's why it still has no appetite.
"The isopods are kept in a tank that uses artificial seawater so it is highly unlikely to generate organic substances such as plankton and sea alga that 'No 1', which is about the same size as its peers in the tank, could feed on."
The aquarium was previously home to a giant isopod that died of natural causes, despite having a healthy appetite, making 'No 1's good health even more mysterious.