The giant Isopod, Bathynomus giganteus (1879)
Phylum : Arthropoda
Subphylum : Crustacea
Class : Malacostraca
Order : Isopoda
Suborder : Cymothoida
Family : Cirolanidae
Genus : Bathynomus (- about 16 other species)
Species : B. giganteus
- Least concern
- 50 cm long and 1,4 kg (size)
- Gulf of Mexico (map)
B. giganteus reaches an average length between 19 and 36 centimetres, with a maximum weight and length of approximately 1.7 kilograms and 76 centimetres respectively. Giant isopods are a good example of deep-sea gigantism. Though most other species of Bathynomus apparently are smaller, they are nevertheless far larger than the “typical” isopods that range in size from 1 to 5 centimetres.
Their morphology resembles that of their terrestrial cousin, the woodlouse: their bodies are dorso-ventrally compressed, protected by a rigid, calcareous exoskeleton composed of overlapping segments. Like the woodlouse, they also possess the ability to curl up into a “ball”, where only the tough shell is exposed. This provides protection from predators trying to strike at the more vulnerable underside. The first shell segment 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.