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The Decapod Leg

The leg in arthropods is, like the rest of the animal, composed of a number of jointed segments. The limbs of different decapods vary hugely, but it is possible to identify a general, shared structure.

Explanation of abbreviations

pC: Precoxa
C: Coxa
B: Basis
I: Ischium

One of the most important features of the decapod limb is the nature of the dactylus. If pincers are present, it is known as chelate (achelate if they are absent). The number of limbs and the position of the limbs with chelae are used in the classification of lower levels, but the gill structure has greater implications for higher taxa.

There are three main types of gill structure in decapods. Phyllobranchiate decapods (as shown in the diagram above) have the gill filaments arranged into two rows, similar to an open book, trichobranchiate (as the name suggests) have three rows of gills filaments branching from a main axis and finally, dendrobranchiate have numerous branching gill fillaments, giving the impression of a bush or tree. To find out more about the classification of decapods, click here