The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen).[1][2] Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. They are, from head to tail:
The head also bears the (usually stalked) compound eyes. The distal portion of a mandible or maxilla which has a sensory function is known as a palp.
Thorax / pereonedit
first maxillipeds
second maxillipeds
third maxillipeds
first pereiopods
second pereiopods
third pereiopods
fourth pereiopods
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. They are also the ten legs from which decapods take their name.[2] Those pereiopods which are armed with a claw (chela) may be referred to as chelipeds. The moveable fingers of a claw are known as dactyls. 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. 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. 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.
Abdomen / pleonedit
Folded abdomen of a cooked crab severed from its body, showing its pleopods hiding beneath.
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. 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.
Telsonedit
At the end of the pleon is the tail fan, comprising a pair of biramousuropods and the telson, which bears the anus. Together, they are used for steering while swimming, and in the caridoid escape reaction.
In crabs and some other carcinised decapods, the abdomen is folded under the cephalothorax.
^ abRobert P. D. Crean (November 14, 2004). . Order Decapoda. University of Bristol. Archived from the original on November 10, 2013. Retrieved April 23, 2012.
January 01, 1970
decapod, anatomy, decapod, crustaceans, such, crab, lobster, shrimp, prawn, made, body, segments, grouped, into, main, body, parts, cephalothorax, pleon, abdomen, each, segment, possess, pair, appendages, although, various, groups, these, reduced, missing, the. The decapod crustaceans such as a crab lobster shrimp or prawn is made up of 20 body segments grouped into two main body parts the cephalothorax and the pleon abdomen 1 2 Each segment may possess one pair of appendages although in various groups these may be reduced or missing They are from head to tail AntennulesPereiopodsCarapacePleopodsTelson Contents 1 Cephalothorax 1 1 Head 1 2 Thorax pereon 2 Abdomen pleon 3 Telson 4 See also 5 ReferencesCephalothorax editHead edit antennules antennae mandibles first maxillae second maxillae The head also bears the usually stalked compound eyes The distal portion of a mandible or maxilla which has a sensory function is known as a palp Thorax pereon edit first maxillipeds second maxillipeds third maxillipeds first pereiopods second pereiopods third pereiopods fourth pereiopods 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 They are also the ten legs from which decapods take their name 2 Those pereiopods which are armed with a claw chela may be referred to as chelipeds The moveable fingers of a claw are known as dactyls 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 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 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 Abdomen pleon edit nbsp Folded abdomen of a cooked crab severed from its body showing its pleopods hiding beneath first pleopods second pleopods third pleopods fourth pleopods fifth pleopods 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 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 Telson editAt the end of the pleon is the tail fan comprising a pair of biramous uropods and the telson which bears the anus Together they are used for steering while swimming and in the caridoid escape reaction In crabs and some other carcinised decapods the abdomen is folded under the cephalothorax nbsp The anatomy of krill using Euphausia superba as a model nbsp The pleopods of Euphausia superba nbsp Crab moult with carapace lifted exposing gills See also editArthropod legReferences edit Gary C B Poore 2004 Glossary Marine Decapod Crustacea of Southern Australia a Guide to Identification CSIRO Publishing pp 549 556 https books google co uk books id ZZWnuGc0xlMC amp pg PA549 ISBN 9780643069060 a b Robert P D Crean November 14 2004 Characters and Anatomy Order Decapoda University of Bristol Archived from the original on November 10 2013 Retrieved April 23 2012 Retrieved from https en wikipedia org w index php title Decapod anatomy amp oldid 1195040009 Thorax 2F Pereon, wikipedia, wiki, book, books, library,
