Hermit Crab Abdominal Appendages – Coenobita species

Hermit crabs in the Coenobita family are Decapods which means they have 10 legs, limbs or appendages.

The abdominal appendages of the land hermit crab include the thoracic appendages, pleopods, uropods and telson [1].
The thoracic appendages are used for cleaning the gills, gripping the shell, gripping a mate during copulation.

The pleopods are used for brooding eggs.

At 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.

The two smaller legs are used for gripping the shell. The uropod on the tip of the abdomen contains the anus and also grips the shells. Photo credit: Moa Lundberg
Female hermit crabs have pleopods to hold their eggs. Photo credit: Moa Lundberg
Coenobita violascens have a very long abdomen compared to other Coenobita species. Photo credit: Moa Lundberg

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Overview of the anatomy of a land hermit crab (Coenobita)

References:
1. Dardanus megistos by Storm Martin 2012

2. Robert P. D. Crean (November 14, 2004). “Characters and Anatomy”. Order Decapoda. University of Bristol. Retrieved April 23, 2012.