---
title: Gem Chiton (Acanthopleura gemmata)
scientific_name: Acanthopleura gemmata
common_name: Gem Chiton
taxon: Chitons
published: 2026-08-11T06:47:06.991Z
updated: 2026-08-11T06:53:05.398Z
tags: Gem Chiton, Acanthopleura gemmata, Chitons, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/chitons/gem-chiton
---

# Gem Chiton (*Acanthopleura gemmata*)

## Quick facts

- **Group:** Chitons (*Polyplacophora*)
- **Size:** up to 10 cm
- **Depth:** 0-2 m
- **Diet:** Herbivore
- **Activity:** Nocturnal
- **Rarity:** Common
- **Habitat:** Intertidal rock, clamped in place by day
- **Reproduction:** Broadcast spawner, Gonochoric

## How to recognise it

- oval body armored with eight overlapping plates
- thick girdle around the plates, bristly and dark
- clamped hard onto intertidal rock, usually in a shallow home scar
- length up to 10 cm

An oval slab of armor on the rocks at the waterline: eight overlapping plates surrounded by a tough bristly girdle, up to 10 cm (4 in) long, clamped down so hard that a finger cannot shift it. Chitons are molluscs built like nothing else, and the segmented shell lets the animal bend over an uneven surface where a limpet's single cone would leak.

It grazes algae at night and returns to the same spot before dawn, over generations wearing a shallow home scar into the rock that fits its outline exactly. The scraping is done with a radula tipped in magnetite - the animal grows iron oxide into its teeth, giving it one of the hardest biological materials known, and it needs it: this is a herbivore whose food grows as a film on stone.

The plates carry something stranger still. Chitons of this group have hundreds of tiny eyes embedded in the shell itself, each with a lens of aragonite, so the animal sees through its own armor. They resolve shapes well enough to trigger a clamp-down before a shadow becomes a predator.

## Also known as

- **English:** Jewelled Chiton
- **Italian:** Chitone gioiello
- **Japanese:** オニヒザラガイ
- **Chinese:** 鬼石鱉
- **Russian:** Хитон самоцветный

## Scientific synonyms

- *Acanthopleura balansae* Rochebrune, 1882
- *Acanthopleura bergenhayni* Leloup, 1937
- *Acanthopleura gemmata maudensis* Ashby, 1928
- *Acanthopleura gemmata queenslandica* Ashby, 1923
- *Acanthopleura glareosa* E. A. Smith, 1884
- *Acanthopleura rawakiana* Rochebrune, 1882
- *Acanthopleura spicifera* [sic]
- *Acanthopleura spiniger* (G. B. Sowerby II, 1839)
- *Acanthozostera virens* Ang, 1967
- *Chiton gemmatus* Blainville, 1825
- *Chiton macgillivrayi* A. Adams, 1855
- *Chiton spiniger* G. B. Sowerby II, 1839

## Range

Marquesas Islands, Mediterranean Sea - Eastern Basin, Mozambique Channel

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/chitons/gem-chiton)*
*Updated: August 11, 2026*