pereiopod , auch: pereopod

They may be easily recognised by their third pereiopod (walking leg), which is greatly enlarged.

Adults have no eyes, and are missing the last segment of the first pereiopod, which is therefore unable to form a claw.

Each appendage from the second maxilla to the fifth pereiopod also bears a gill.

Mature females have a small claw on the fifth pereiopod, and enlarged pleopods.

The chelipeds are usually robust, and in some the last pereiopod pair has ovate dactyls.

A single pereiopod (walking leg) is visible, and it ends without a chela (claw).

The most distinctive characteristics of Engystenopus are characters of the third pereiopod, which was lacking from all the early specimens.

The ground colour is transparent, but the carapace, abdomen and the large third pereiopod are all banded red and white.

The two species are found in different oceans, and can be distinguished by the pattern of setation on the claw of the first pereiopod.

The last two pairs of pereiopods are simple (without claws), except in Thaumastocheles, where the fifth pereiopod may have "a minute pincer".

The claw-bearing legs (chelipeds, the first pereiopod pair) are much longer and somewhat elongated in males than they are in females.

The first pereiopod is modified into a strong cheliped (claw-bearing leg): the claw's fingers, the dactylus and propodus, are black at the tips.

The pereiopods bear the sexual organs, which are the third pereiopod in the female and the fifth pereiopod in the male.

They are characterised by the subdivided carpus of the second pereiopod and, mainly, by the lack of the chelae (claws) on the first pereiopod.

It may be distinguished from other species by the form of the first pereiopod; the carpus (last segment before the claw) of that leg bears a lobe which projects forwards.

These larvae can be distinguished from other palinurid larvae by their pereiopods 4 and 5 being already present as small buds and by the long, non-setose exopod on pereiopod 3.

However, P. texana only occurs in the Gulf of Mexico, and can be distinguished from P. sayi by the form of the fifth pereiopod (last walking leg) and that of the male gonopod.

It differs from Atya by various characters, including the form of the telson (which is longest at the corners in Atyopsis, but not in Atya) and the presence of a "massive spur" on the male third pereiopod.

Fenner A. Chace considered it to be the sister group to the much larger superfamily Palaemonoidea, with which it shares the absence of endopods on the pereiopods, and the fact that the first pereiopod is thinner than the second.

Any organs which are absent from the adults do not generally appear in the larvae, although there are a few exceptions, such as the vestige of the fourth pereiopod in the larvae of Lucifer, and some pleopods in certain Anomura and crabs.