The Giant Isopod
The Giant Isopod. Scientists call it Bathynomus Giganteus. Thought to be abundant in the cold murky depths of the Atlantic Ocean, it is the largest known Isopod in the world. Let’s take a closer look at the giant isopod
French zoologist Alphonse Milne-Edwards was the first to describe the genus in 1879 after fishing a juvenile male B. giganteus from the Gulf of Mexico.
The Giant Isopod matures to a length between 19 and 37 centimeters (7.5 and 15 inches), and reaches a maximum weight of approximately 1.7 kilograms (3.7 lb). It bears a striking resemblance to the wood lice or potato bug.
Giant Isopods have large eyes that are compound with nearly 4,000 facets. They are also sessile (permanently attached, do not move) and spaced far apart on the head. They also have two pairs of antennae.
The Giant Isopod’s thoracic legs or pereiopods are arranged in seven pairs, the first of which are modified into maxillipeds to manipulate and bring food to the four sets of jaws.
Giant Isopods are important scavengers in the deep-sea environment; they are found at a depth of 170 meters (560 ft) to the pitch darkness of 2,140 meters (7,020 ft), where pressures are high and temperatures are very low – down to about 4 °C (39 °F). Over 80% are found at a depth between 365 and 730 meters (1,198 and 2,395 ft). They are thought to prefer a muddy or clay substrate and lead solitary lives.
Although generalist scavengers, these Giant Isopods are mostly carnivorous and feed on dead whales, fish, and squid; they may also be active predators of slow-moving prey such as sea cucumbers, sponges, radiolarians, nematodes, and other zoobenthos, and perhaps even live fish. They are also known to attack trawl catches. As food is scarce in the deep ocean, giant isopods must make do with what fortune brings; they are adapted to long periods of famine and have been known to survive over eight weeks without food in the aquariums of irresponsible owners
Eggs of the Giant Isopod are also giant, up to 13mm diameter (0.5 inches) and are brooded in a brood pouch above the stomach and internal organs. Females do not feed when brooding and seem to bury themselves in the sediment to reduce energy expenditure during brooding, which would insulate them and protect the brood and adults from predators.
This unfortunately appears to make them more susceptible to trawls since brooding females have only been caught in trawls and not baited traps. Juveniles of Bathynomus giganteus are called mancas and reach length up to 6cm (2.36 in). Mancas are characterized by the lack of the seventh pair of pereopods.
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