Taxonomy of Shellfish

Unit 3 - General characters of Order Decapoda

3.1.Order 2. Decapoda

• The Decapoda contains the biggest crustaceans like prawns, lobsters and crabs.
• The head and thorax fused to form a cephalothorax.
• The carapace fused to all the thoracic somites and also extends to the sides covering the gills and forming a branchial chamber.
• The expodite of the second maxillae has a well developed scale.
• The first three thoracic appendages modified as maxillipeds, and the rest as pereopods, some of which may be chelate.
• The pleopods biramous.
• Three series of branchiae are usually present, the podobranchiae on the coxae of legs, the arthrobranchiae on the arthroidal membranes and pleurobranchiae on the sides of thoracic wall.
• A statocyst usually present on the proximal segment of the antennae.

The order Decapoda is the largest and most highly organised crustacea. It includes about 8,500 species, representing almost one-third known species of crustacea.

Decapoda is divided into two sub-orders. They are,

• Natantia and
• Reptantia