---
title: Spiny Sea Squirt (Halocynthia spinosa)
scientific_name: Halocynthia spinosa
common_name: Spiny Sea Squirt
taxon: Sea squirts
published: 2026-08-08T18:49:37.736Z
updated: 2026-08-08T21:20:59.890Z
tags: Spiny Sea Squirt, Halocynthia spinosa, Sea squirts, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/spiny-sea-squirt
---

# Spiny Sea Squirt (*Halocynthia spinosa*)

## Quick facts

- **Group:** Sea squirts (*Ascidiacea*)
- **Size:** up to 10 cm tall
- **Depth:** 5-40 m
- **Diet:** Filter feeder
- **Activity:** Cathemeral
- **Rarity:** Uncommon
- **Habitat:** Rock and dead coral on shaded slopes
- **Reproduction:** Broadcast spawner, Simultaneous hermaphrodite

## How to recognise it

- tough leathery body covered in short spines
- orange to reddish, siphons often ringed paler
- grows singly, firmly attached to rock
- height up to 10 cm

A solitary sea squirt with a tough leathery tunic covered in short spines, orange to reddish, its two siphons frequently ringed in a paler shade. It grows singly on rock and dead coral, up to about 10 cm (4 in) tall, and is stiff enough to keep its shape out of water.

The tunic is the feature that names the whole subphylum: it is built largely of cellulose, which no other animal produces, and it functions as armour, anchor and skeleton at once. The spines add grit to that defence, and the result is an animal almost nothing eats. Water is drawn through a pharyngeal basket pierced by thousands of slits, and everything edible in it is trapped on a moving sheet of mucus - a filtering method so effective that a colony of sea squirts can clear a measurable fraction of the water passing over a reef.

## Also known as

- **French:** Ascidie épineuse
- **Russian:** Асцидия колючая

## Scientific synonyms

- *Halocynthia arabica* Monniot C., 1965
- *Halocynthia defectiva* Millar, 1962

## Range

Djibouti, Federal Republic of Somalia, Indian Ocean, North Atlantic Ocean, Red Sea, South Africa

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/spiny-sea-squirt)*
*Updated: August 8, 2026*