Crayfish Diagram Labeled – External Anatomy

All 12 parts on the diagram

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Start here: 7 main parts 7

Cephalothorax The front of the two main body parts. Head and thorax joined, carrying the eyes, antennae, mouthparts and legs.
Carapace The shell covering the cephalothorax, protecting the internal organs and the gills.
Antennae The long feelers on the head, the second pair of head appendages.
Chelipeds Legs armed with a claw, called a chela. On this crayfish they are the big front pair.
Walking legs The legs behind the claws, used mainly for walking and gathering food. With the chelipeds they make the ten legs of a decapod.
Abdomen The back of the two main body parts, made of segments.
Telson The central plate at the end of the abdomen. Part of the tail fan.

The front: 6 3

Rostrum Part of the carapace that sticks out in front of the eyes.
Compound eyes The eyes, usually on stalks, on the head.
Antennules The short first pair of head appendages, each forked in two.

The tail: 4 2

Swimmerets Small legs under the abdomen. Used mainly for swimming and, in females, for carrying eggs.
Uropods The paired side plates of the tail fan. With the telson they steer while swimming and power the quick backward escape.

How this list was compiled: Read 2026-09-26. Wikipedia, Decapod anatomy, https://en.wikipedia.org/wiki/Decapod_anatomy : the body in two main parts, the cephalothorax and the pleon (abdomen), of segments with paired appendages; the head's antennules, antennae, mouthparts and usually stalked compound eyes; the pereiopods as walking legs used also to gather food, the ten legs of a decapod, those with a claw (chela) called chelipeds; the carapace covering the cephalothorax and protecting the organs and gills, its part projecting in front of the eyes called the rostrum; the pleopods (swimmerets) as swimming legs also used to brood eggs; the tail fan of paired uropods and the telson, used for steering and the escape reaction. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

A crayfish diagram labeled from above, the way a lab specimen lies in the tray: the shell-covered front, the claws and legs, and the segmented tail ending in its fan. Start with the 7 main parts.

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The front half

The cephalothorax is the head and thorax together, covered by the carapace. The rostrum points forward between the stalked compound eyes. The short forked antennules and long antennae are feelers.

Legs and tail

A crayfish is a decapod, with ten legs: the clawed chelipeds and four pairs of walking legs. Behind them the abdomen carries swimmerets underneath and ends in the tail fan, the telson with a uropod on each side.

Count the legs: two chelipeds plus eight walking legs make the ten that give decapods their name.

Questions and answers

What are the two main body parts of a crayfish?

The cephalothorax, the head and thorax joined under the carapace, and the abdomen, the segmented tail.

What are swimmerets used for?

They are small legs under the abdomen, used mainly for swimming. Females also use them to carry their eggs.

What is the difference between the telson and the uropods?

The telson is the middle plate at the end of the tail; the uropods are the paired plates beside it. Together they form the tail fan used for steering and quick escapes.