---
title: Sea squirts (Ascidiacea)
scientific_name: Ascidiacea
common_name: Sea squirts
rank: Class
published: 2024-11-19T18:41:51.573Z
updated: 2026-08-03T21:15:42.474Z
tags: Sea squirts, Ascidiacea, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts
---

# Sea squirts (*Ascidiacea*)

## Quick facts

- **Rank:** Class
- **Scientific name:** Ascidiacea
- **Body shape:** Irregular - No standard fish outline - seahorses, frogfishes, ghost pipefishes.
- **Species listed here:** 12

## How to recognise this group

- sessile, firmly attached to rocks or other substrates
- sac-like, blob-shaped, or forming encrusting colonies
- two distinct openings (siphons) on the surface
- often brightly coloured in reds, yellows, blues, or purples
- contract rapidly and squirt jets of water when disturbed

Sea squirts are sessile marine invertebrate filter feeders, sac-like in form. They vary from individual sacs (solitary species) to clustered communities (social ascidians), or large encrusting colonies formed by numerous small individuals, called zooids, embedded in a common tunic (compound ascidians). Sizes range from a few millimetres to over 30 cm (1 ft) across. While many species are drab, others display vivid colours such as reds, yellows, blues, and purples.

Sea squirts firmly attach themselves to substrates like rocks, coral rubble, and artificial structures across all reef zones, from the intertidal to depths of at least 60 m (200 ft). They feed by drawing in seawater through an oral siphon and expelling filtered water through an atrial siphon, extracting phytoplankton and suspended particulate matter. When disturbed, many species rapidly contract, expelling jets of water from their siphons. They are commonly encountered by divers.


## Species (12)

- [Black Colonial Ascidian (Botrylloides niger)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/black-colonial-ascidian)
- [Black-mouth Ascidian (Ascidia melanostoma)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/black-mouth-ascidian)
- [Blue Club Tunicate (Rhopalaea idoneta)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/blue-club-tunicate)
- [Brick Ascidian (Eusynstyela latericius)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/brick-ascidian)
- [Eilat Star Ascidian (Botryllus eilatensis)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/eilat-star-ascidian)
- [Herdmania momus (Herdmania momus)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/herdmania-momus)
- [Manina's Ascidian (Metandrocarpa manina)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/maninas-ascidian)
- [Ridged Sea Squirt (Pyura gangelion)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/ridged-sea-squirt)
- [Rodrigues' Didemnum (Didemnum rodriguesi)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/rodrigues-didemnum)
- [Sheep's Foot Ascidian (Polycarpa mytiligera)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/sheeps-foot-ascidian)
- [Spiny Sea Squirt (Halocynthia spinosa)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/spiny-sea-squirt)
- [Turkish Ascidian (Rhodosoma turcicum)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/turkish-ascidian)

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts)*
*Updated: August 3, 2026*