A giant isopod may be one of approximately nine species of large isopods (crustaceans related to the shrimps and crabs) in the genus Bathynomus. They are thought to be abundant in cold, deep waters of the Atlantic. Bathynomus giganteus, the species upon which the generitype is based, is the largest known isopod and is the one most often referred to by the common name "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; this was an exciting discovery for both scientists and the public, as at the time the idea of a lifeless or "azoic" deep ocean had only recently been refuted by the work of Sir Charles Wyville Thomson and others. Females were not recovered until 1891.

 

Giant isopods are of little interest to most commercial fisheries owing to the typical paucity of catches and because ensnared isopods are usually scavenged beyond marketability before they are recovered. However, in Northern Taiwan and other areas, they are not uncommon at seaside restaurants, served boiled and bisected with a clean lateral slice. The white meat, similar to crab or lobster in texture, is then easily removed. The few specimens caught in the West with baited traps are sometimes seen in public aquaria.

Maturing to a length between 19 and 37 cm (7.5 to 14.5 in), and maximally reaching a weight of approximately 1.7 kg (3 lb) in B. giganteus,giant isopods are a good example of deep-sea gigantism; most other isopods range in size from 1–5 cm. Their morphology is nonetheless familiar to most people as giant isopods closely resemble their terrestrial cousins, the woodlice: their bodies are dorso-ventrally compressed, protected by a rigid, calcareous exoskeleton composed of imbricate segments. The first of these segments is fused to the head; the most posterior segments are often fused as well, forming a "caudal shield" over the shortened abdomen (pleon). The large eyes are compound with nearly 4,000 facets, sessile and spaced far apart on the head . There are two pairs of antennae.

The uniramous 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. The abdomen has five segments called pleonites each with a pair of biramous pleopods; these are modified into natatory legs and rami, flat respiratory structures acting as gills. The isopods are a pale lilac in colour.

Submitted by : Martin G.

Giant isopods are important scavengers in the deep-sea benthic environment; they are found from the gloomy sublittoral zone at a depth of 170 m (550 ft) to the pitch darkness of the bathypelagic zone at 2,140 m (7,020 ft), where pressures are high and temperatures are very low (down to about 4°C). Over 80% are found at a depth between 365 m and 730 m . They are thought to prefer a muddy or clay substrate and lead solitary lives.

 

Although generalist scavengers, these 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 known to attack trawl catches. As food is scarce in the deep ocean biome, 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 aquarium.

When a significant source of food is encountered, giant isopods gorge themselves to the point of compromising their locomotive ability.

One study examining the contents of 1651 giganteus' guts found that fish were most common there, followed by cephalopods and decapods, particularly carideans and galatheids.

 

You don't see the video above?