Antennules

Pereiopods

Carapace

Pleopods

Uropods

Telson

The decapod crustacean, such as a crab, lobster, shrimp or prawn, is made up of nineteen body segments grouped into two main body parts, the cephalothorax and the abdomen. The decapods or Decapoda ( literally means "ten footed") are an order of Crustaceans within the class Malacostraca, including many Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting Segmentation in biology refers to the division of some Metazoan bodies and Plant body plans into a series of semi-repetitive segments and the question of The cephalothorax (call prosoma in some groups is an anatomical term used in Arachnids and Malacostracan Crustaceans for the In Vertebrates such as Mammals the abdomen (belly constitutes the part of the body between the Thorax (chest and Pelvis. Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. An appendage in the broadest sense is an additional or subsidiary part existing on or added to something which can generally still function if the appendage has never existed or They are, from head to tail:

Cephalothorax

Head

1. antennules
2. antennae
3. mandibles
4. first maxillae
5. second maxillae

The head also bears the (usually stalked) compound eyes. Antennae (singular antenna) are paired Appendages connected to the front-most segments of Arthropods In Crustaceans they are In arthropods the mandible is either of a pair of Arthropod Mouthparts used for biting cutting and holding food In certain Arthropods the maxillae are paired Mouthparts located behind the mandibles. In certain Arthropods the maxillae are paired Mouthparts located behind the mandibles.

Thorax / Pereon

1. first maxillipeds
2. second maxillipeds
3. third maxillipeds
4. first pereiopods
5. second pereiopods
6. third pereiopods
7. fourth pereiopods
8. fifth pereiopods

Maxillipeds are appendages modified to function as mouthparts. Particularly in the less advanced decapods, these can be very similar to the pereiopods. Pereiopods are primarily walking legs and are also used for gathering food. The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. Those pereiopods which are armed with a claw (chela) are sometimes referred to as chelipeds. The pereiopods bear the sexual organs, which are the third pereiopod in the female and the fifth pereiopod in the male. Each appendage from the second maxilla to the fifth pereiopod also bears a gill. A gill is an anatomical structure found in many aquatic organisms In the Anomura (hermit crabs and related animals), the fifth pair of pereiopods is often hidden inside the branchial chamber, where they are used to clean the gills. Anomura (sometimes Anomala) is a group of decapod Crustaceans including Hermit crabs and others Hermit crabs are decapod Crustaceans of the superfamily Paguroidea. The cephalothorax is covered by a carapace which protects the internal organs and the gills; the section of the carapace that projects in front of the eyes is called the rostrum. A carapace is a dorsal section of an Exoskeleton or shell in a number of animal groups A gill is an anatomical structure found in many aquatic organisms

Abdomen / Pleon

1. first pleopods
2. second pleopods
3. third pleopods
4. fourth pleopods
5. fifth pleopods
6. uropods

Pleopods (also called swimmerets) are primarily swimming legs, and are also used for brooding the eggs (except in prawns), catching food (then swept to the mouth), and can sometimes bear their own gills. Prawns are Crustaceans belonging to the sub-order Dendrobranchiata   In some taxa, the first one or two pairs of pleopods are specialised in the males for fertilisation, and are referred to as the gonopods. At the end of the pleon is the tail fan, comprising a pair of biramous uropods and the telson, which bears the anus. The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. The telson is the last division of the body of a Crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas Together, they are used for steering while swimming, and in the caridoid escape reaction. The Caridoid Escape Reaction, also known as lobstering or tail-flipping, refers to an innate escape mechanism in marine and freshwater Crustaceans

In crabs and some other carcinised decapods, the abdomen is folded under the cephalothorax. Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Carcinisation (or carcinization) is a hypothesised process whereby a Crustacean evolves into a Crab -like form from a non-crab-like form

The anatomy of krill, using Euphausia superba as a model. Antarctic krill ( Euphausia superba) is a Species of Krill found in the Antarctic waters of the Southern Ocean.

The pleopods of Euphausia superba. Antarctic krill ( Euphausia superba) is a Species of Krill found in the Antarctic waters of the Southern Ocean.