---
title: Reef Box Crab (Calappa hepatica)
scientific_name: Calappa hepatica
common_name: Reef Box Crab
taxon: Crabs
published: 2024-06-02T15:23:12.231Z
updated: 2026-08-20T17:09:45.115Z
tags: Reef Box Crab, Calappa hepatica, Crabs, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/reef-box-crab
---

# Reef Box Crab (*Calappa hepatica*)

## Quick facts

- **Group:** Crabs (*Brachyura*)
- **Size:** up to 8 cm
- **Depth:** 1-50 m
- **Diet:** Carnivore
- **Activity:** Nocturnal
- **Rarity:** Uncommon
- **Habitat:** Sand and rubble, buried by day
- **Reproduction:** Brooder, Gonochoric

## How to recognise it

- domed sandy shell with rough ridges, wider than it is long
- claws folded flat against the front, closing the body into a smooth box
- usually buried with only the top of the shell and the eyes showing
- shell up to 8 cm across

A domed sandy crab that folds its claws flat across the front until the whole animal is a smooth box with no gaps - which is where the name comes from, and why a box crab in defense looks like a stone with a seam.

The right claw is a tool. It carries a hooked tooth at the base that works exactly like a can opener: the crab grips a snail shell, hooks the lip, and peels the spiral open turn by turn to reach the animal inside. The left claw holds the shell while the right one works, and the two are visibly different shapes because of it.

It spends the day buried in sand with only the eye slits exposed, and hunts at night for snails, hermit crabs and whatever else it can open.

Because both claws are asymmetrical and specialized, a box crab that loses the right one is in trouble until it molts - which is a hazard of building your living around a single tool.

## Also known as

- **English:** smooth box crab, Common Box Crab, Reef Box Crab
- **French:** Calappe aux longs yeux, Crabe honteux de récif
- **Italian:** calappa del reef
- **Portuguese:** Caranguejo-cofre-de-recife
- **Japanese:** ソデカラッパ
- **Chinese:** 肝葉饅頭蟹
- **TH:** ปูฤๅษีปม

## Scientific synonyms

- *Calappa spinocissima* H. Milne Edwards, 1837
- *Calappa spinosissima* H. Milne Edwards, 1837
- *Calappa tuberculata var. sandwichien* Eydoux & Souleyet, 1842
- *Calappa tuberculosa* Guérin, 1832
- *Calappe spinosissima* H. Milne Edwards, 1837
- *Calappe tuberculata* (Herbst, 1785)
- *Cancer afata* Curtiss, 1938
- *Cancer hepatica* Linnaeus, 1758
- *Cancer tuberculatus* Herbst, 1785

## Range

East Africa, Indian Ocean, Indo-Pacific, Kenya, Madagascar, Mozambique, Mozambique Channel, New Caledonian Exclusive Economic Zone, North Pacific Ocean, Red Sea, Seychelles, South Africa, South Pacific Ocean

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/reef-box-crab)*
*Updated: August 20, 2026*