Giant+Isopod


 * Basic Information **

A **giant isopod** is in the nine species of large isopods in the group //**Bathynomus**//. They are thought to be abundant in cold, deep waters of the Atlantic Ocean. //Bathynomus giganteus//, is the largest known isopod and is called the giant isopod.French zoologist Alphonse Milne-Edwards was the first to discover the giant isopod in 1879. Females were not recovered until 1891.Giant isopods are not hunted a lot and have very little commercial value to fishers. They usually get caught in the fishers' nets. The giant isopod has great resemblance to the pillbug, it can even curl up in a ball like the pillbug does. ** Physical Description ** Growing to an average length between 8 and 14 inches and reaching a weight of 3.7 pounds. Giant isopods are a good example of deep sea-gigantism, most other isopods range in size from 1 to 5 centimetres. Their body resembles that of their cousin, the woodlouse: their bodies are compressed, protected by a rigid, hard exoskeleton made of of overlapping segments. Like the woodlouse, they also possess the ability to curl up into a "ball", where only the shell is exposed. This provides protection. The first shell segment is connected to the head; the other segments ar connected to that one. The large eyes are compound and are spaced far apart on the head. There are two pairs of antennae. The legs are arranged in seven pairs, the first pair are made to bring food to the four sets of jaws. The abdomen has five segments called //pleonites// each with a pair of flipper like legs; these are made into flat structures acting as gills. The isopods are a pale in colour.

** Feeding Habits ** Giant isopods are important scavengers in the deep-sea environment; they are found from the gloomy sublittoral zone at a depth of 560 ft to the pitch darkness of the bathypelagic(deep sea) zone at 7,020 ft, where pressures are high and temperatures are around about 39 °F. Over 80 percent are found at a depth between 1,198 and 2,400 ft. They prefer a muddy or clay area and lead solitary lives. Although scavengers, these isopods are mostly carnivorous and feed on dead whales, fish, and squid; they may also be predators of slow-moving prey such as sea cucumbers, sponges, radiolarians, nematodes, and other zoobenthos, and even live fish. Food is scarce in the deep sea, giant isopods must make do with what they get; they are adapted to long periods of starvation and can survive over eight weeks without food in captivity. When a source of food is found, giant isopods stuff themselves to the point of almost not being able to walk. In 1990, the Scavengers of East Australian Seas expedition (SEAS) started to document giant isopods along the east coast of Australia by setting traps. The deeper the water, the fewer number of species they found and the larger the species tended to be. The giant isopods found in very deep waters off Australia were compared to those found off Mexico and India. From the fossil record it is thought that the giant isopod existed more than 160 million years ago, before the break-up of the supercontinent Pangaea, so it did not evolve in all three locations.

Home Page