Giant Isopod

Bathynomus giganteus — the giant isopod — is the LARGEST KNOWN ISOPOD on Earth and one of about 20 species in genus Bathynomus (the deep-sea giant isopods). The species is widespread in the abyssal depths of the Atlantic, Pacific, and Indian Oceans at depths of 170-2,140 meters. Adults reach 50 cm body length (the largest individuals exceed 50 cm) and 1.7 kg body weight, with a body plan that exactly resembles a giant deep-sea version of the familiar terrestrial pillbug (Armadillidium vulgare — already in the Wild Files): segmented dorsal armor that allows the animal to roll into a defensive ball, seven pairs of walking legs, two pairs of antennae, and the diagnostic isopod 'wood-louse' body shape but at 100x the size of typical pillbugs. The body coloration is grayish-pink-to-pale-violet — typical deep-sea coloration that provides camouflage in the dim abyssal environment. The species' major biological feature is EXTREME METABOLIC CONSERVATION. Giant isopods live in the cold, food-limited deep ocean where prey items (sinking carcasses of larger marine animals — whales, sharks, large fish) arrive at the seafloor irregularly and unpredictably. The species has evolved one of the slowest metabolic rates of any marine arthropod and the ability to SURVIVE MULTI-YEAR PERIODS BETWEEN MEALS without feeding. Captive giant isopods at the Toba Aquarium in Japan have been documented to FAST FOR FIVE YEARS AT A TIME without consuming any food — an individual named 'No. 1' survived from January 2007 to February 2014 (over 5 years) without eating before dying in 2014. The fasting capability is achieved through extreme metabolic conservation: the isopod barely moves, maintains low body temperature in the cold abyssal water (4-10°C), and gradually consumes stored body lipids accumulated during previous feeding events. The species is a SCAVENGER on sinking marine carcasses (whale falls, shark carcasses, large fish carcasses) and an OPPORTUNISTIC PREDATOR on slow-moving deep-sea invertebrates. When food is encountered, giant isopods feed VORACIOUSLY — feeding events documented in baited camera traps show dozens of giant isopods converging on a sinking whale carcass and consuming the entire animal over weeks. The species is the deep-sea representative of order Isopoda — the same group that includes terrestrial pillbugs (Armadillidium), beach hoppers (sand fleas), and many marine isopods. The species is one of the most-Googled deep-sea creatures and a flagship subject of deep-sea biology outreach. The species is harmless to humans (not encountered in normal recreational diving — the species lives below recreational dive depths).