Giant Isopod No. 1


Odd Creatures is a recurring column about the world’s weirdest species written by award-winning science writer and author Bec Crew, and illustrated by the super-talented Aiyana Udesen


On 9 September 2007, a giant isopod was scooped from the waters of Baja California and transported to Toba Aquarium on Japan’s east coast. Home to some 25,000 sea creatures from 1,000 species, Toba Aquarium has a pretty extensive collection, but their new isopod made an instant impression. Named “No. 1”, this huge, pill bug-looking crustacean stretched almost a foot long, weighed over 2 pounds, and was the first of the aquarium’s eight giant isopods.

In the wild, giant isopods are enthusiastic and voracious scavengers, feeding off whale, fish and squid carcasses, and sometimes even slow-moving live prey, such as sponges and sea cucumbers, and even a sluggish fish or two, if they’re really lucky. Sometimes they’ll even have a go at an underwater cable, because when you’re a giant isopod, almost anything could potentially be a meal. In captivity, they’ve got things even easier, receiving hand-fed meals of horse mackerel.

No. 1 got pretty used to his cushy lifestyle at Toba Aquarium, and became a real hit with the public. But then, on 2 January 2009, something strange occurred. No. 1 nibbled on a hearty 50-gram chunk of mackerel before pushing the rest away and embarking on the world’s most bizarre hunger strike.

“No. 1’s caretaker, Takeya Moritaki, couldn’t figure out what was wrong,” says Robert Krulwich at NPR. “He tried pushing the food closer. No. 1 didn’t care. He tried different foods. No. 1 wasn’t interested. It would either push the food away, or walk away. He tried sticking No. 1’s face into the food. Nothing. He even tried changing the temperature to make No. 1 hungrier, or more comfortable. Still nothing.”

The years passed – 2010, 2011, 2012, 2013 – and still nothing. “I just want it to eat something somehow. It’s weakened in this state,” Moritaki told Rocket News, his head in his hands. Of course, No. 1’s mysterious statement captured the imagination of everyone who heard about it, and a handful of photographers and journalists would turn up for every feeding session – which became fewer and further between as the years crept on – in the hopes of witnessing the end of what was quickly becoming a record-breaking fast.

According to Rocket News, No. 1 even tried to trick everyone into thinking it was eating, by rubbing its mouthparts on its food and moving it around with its front legs – so basically the giant isopod equivalent of stubbornly shoving its meal around on its plate – without ever taking a bite.

Then on February 14th, 2014 – which happens to be some kind of strange underwear commemoration in Japan called Fundoshi Day – Moritaki noticed something was seriously wrong with No. 1. After five years and 43 days of zero food – not one tiny morsel – No. 1 had finally passed away. Said to be one of the longest known fasts of any animal ever, the aquarium staff dissected the carcass to see what could have caused it. Maybe there was some kind of blockage, some weird physical defect that was preventing No. 1 from eating? Nope, everything looked as it should.

Whether it was sickness, sadness, or some strange form of isopod ennui, something prompted No. 1 to reject his food, and he took his secret with him to the grave. He has now been frozen for preservation.

Here he is in all his mysterious glory:


—Bec Crew / @BecCrew

2 Comments, Comment or Ping

  1. David Brown

    Looking at the relative size of the tank, Isopod No.1 was stuck into the equivalent of a small, glass walk-in closet. I’m surprised he lasted 7 years. Maybe even isopods understand the futility of confined living and isolation. He was used to scavenging for food in the wild then he was stuck in a small glass cube to be ogled while going about a very un-stimulating and unnatural existence.

  2. Howard Vickridge

    I’d love to know if there’s a chance No.1 derived nutrition from food that wasn’t obvious – like filtering through scraps in the water or photosynthesising or breaking down mud/soil/rock. The chemistry of this organism expending energy for 7 years with nothing more than water and light (implied by the story) doesn’t appear to pass the ‘common-sense’ test. 7 years of respiration and movement – no mention of hibernation but just a progressively weakened state. Maybe a physicist could do the energy calculations of weight loss vs. energy consumed? A mystery it is indeed.

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