A
Giant Isopod may be one of approximately nine species of large isopods (crustaceans related to the shrimp 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 Americas with baited traps are sometimes seen in public aquaria.
Maturing to a length between 19 and 37 centimetres (7.5 and 15 in), and maximally reaching a weight of approximately 1.7 kilograms (3.7 lb) in B. giganteus, giant isopods are a good example of deep-sea gigantism (cf. giant squid); most other isopods range in size from 1 to 5 centimetres (0.39 to 2.0 in). Their morphology is nonetheless familiar to most people as giant isopods closely resemble their terrestrial cousin, the woodlouse: 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.