---
title: Harlequin Swimming Crab (Lissocarcinus orbicularis)
scientific_name: Lissocarcinus orbicularis
common_name: Harlequin Swimming Crab
taxon: Crabs
published: 2026-08-08T21:11:47.339Z
updated: 2026-08-09T05:38:09.741Z
tags: Harlequin Swimming Crab, Lissocarcinus orbicularis, Crabs, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/harlequin-swimming-crab
---

# Harlequin Swimming Crab (*Lissocarcinus orbicularis*)

## Quick facts

- **Group:** Crabs (*Brachyura*)
- **Size:** up to 1.5 cm
- **Depth:** 1-30 m
- **Diet:** Detritivore
- **Activity:** Nocturnal
- **Rarity:** Uncommon
- **Habitat:** On and inside sea cucumbers
- **Reproduction:** Brooder, Gonochoric

## How to recognise it

- bold chocolate-and-cream blotches, like a harlequin costume
- smooth rounded shell, flattened swimming legs
- found riding on a sea cucumber, rarely on open bottom
- width under 1.5 cm

A small crab in a chocolate-and-cream pattern so contrasty it looks painted, with a smooth rounded shell and the flattened rear legs of a swimming crab. Width stays under 1.5 cm (0.6 in).

It lives on sea cucumbers, and that is where to look for it - riding the flank of a large holothurian, or tucked into the folds around the mouth. Some individuals go further and live inside the host's gut, coming out to feed. The crab takes mucus and food particles from the sea cucumber's surface and gains a walking fortress that predators avoid because of the saponins in its skin; the holothurian appears to lose nothing. Colour varies with the host species, dark on a pale animal and pale on a dark one, which is the usual reason a diver misses one. Look on Bohadschia and the larger Holothuria after dark.

## Also known as

- **English:** sea cucumber crab, sea cucumber swimming crab
- **French:** Crabe arlequin des holothuries
- **German:** Seegurken-Schwimmkrabbe
- **Spanish:** Jaiba Payaso
- **Japanese:** ナマコマルガザミ
- **Russian:** Краб-арлекин

## Scientific synonyms

- *Lissocarcinus pulchellus* Müller, 1887

## Range

Comoros, Indian Ocean, Madagascar, Mozambique, Mozambique Channel, New Caledonian Exclusive Economic Zone, Northern and Central Red Sea, Republic of Mauritius, Seychelles, South Africa, South Pacific Ocean, Southern Red Sea, Tanzania

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/harlequin-swimming-crab)*
*Updated: August 9, 2026*