---
title: Black Colonial Ascidian (Botrylloides niger)
scientific_name: Botrylloides niger
common_name: Black Colonial Ascidian
taxon: Sea squirts
published: 2026-08-08T18:49:37.767Z
updated: 2026-08-08T19:02:51.999Z
tags: Black Colonial Ascidian, Botrylloides niger, Sea squirts, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/black-colonial-ascidian
---

# Black Colonial Ascidian (*Botrylloides niger*)

## Quick facts

- **Group:** Sea squirts (*Ascidiacea*)
- **Size:** colonies to 20 cm across
- **Depth:** 0-20 m
- **Diet:** Filter feeder
- **Activity:** Cathemeral
- **Rarity:** Common
- **Habitat:** Encrusting harbour walls, wrecks and shaded rock
- **Reproduction:** Brooder, Budding, Simultaneous hermaphrodite

## How to recognise it

- dark encrusting sheet with animals in meandering double rows
- black to deep purple, sometimes with orange siphon rims
- surface smooth and slightly glossy when submerged
- colonies up to 20 cm across

A dark encrusting colony - black through deep purple, sometimes with orange around the siphons - in which the animals are laid out in meandering double rows rather than the neat stars of its relative. It covers shaded rock, wreck plating and harbour walls in sheets up to about 20 cm (8 in).

This is one of the world's more successful hitchhikers, carried between ports on hulls and now established well outside its original range, which is why identifying it anywhere involves the question of where it actually came from. Unlike most ascidians it broods its larvae inside the colony and releases them ready to settle within hours, so a fouled hull seeds a new harbour quickly. On natural reef here it takes shaded, sheltered surfaces, and a colony overgrowing dead coral will sometimes be found being eaten by a nudibranch specialised on exactly this prey.

## Also known as

- **English:** black synascidia
- **French:** synascidie noire
- **Russian:** Ботриллоидес чёрный

## Scientific synonyms

- *Botrylloides chazaliei* Sluiter, 1898
- *Botrylloides nigrum* Herdman, 1886
- *Botryllus niger* (Herdman, 1886)
- *Botryllus nigrum* (Herdman, 1886)
- *Metrocarpa nigrum* (Herdman, 1886)

## Range

South Atlantic Ocean

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