---
title: Blue Club Tunicate (Rhopalaea idoneta)
scientific_name: Rhopalaea idoneta
common_name: Blue Club Tunicate
taxon: Sea squirts
published: 2026-08-08T18:49:37.721Z
updated: 2026-08-08T19:17:57.017Z
tags: Blue Club Tunicate, Rhopalaea idoneta, Sea squirts, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts/blue-club-tunicate
---

# Blue Club Tunicate (*Rhopalaea idoneta*)

## Quick facts

- **Group:** Sea squirts (*Ascidiacea*)
- **Size:** up to 8 cm tall
- **Depth:** 3-40 m
- **Diet:** Filter feeder
- **Activity:** Cathemeral
- **Rarity:** Uncommon
- **Habitat:** Shaded reef walls and overhangs
- **Reproduction:** Broadcast spawner, Simultaneous hermaphrodite

## How to recognise it

- translucent blue vase-shaped body with two openings
- grows singly or in small clusters, not as a sheet
- internal structures visible through the tunic
- height up to 8 cm

A translucent blue vase standing from shaded rock, up to about 8 cm (3 in) tall, with two openings at the top - a larger one that draws water in and a smaller that sends it out. The body wall is clear enough that the internal basket shows through, which is what makes this species worth a close photograph.

A sea squirt is a far closer relative of a fish than of anything else on the reef. Its larva is a tadpole with a notochord, a nerve cord and a tail, and it swims until it finds a surface, cements itself head-down and then digests most of its own brain, since a sessile animal has little use for one. What remains is a pump: water in through the big siphon, food strained out on a mucus net, water out through the small one. The blue colour comes from pigment in the tunic rather than from anything living inside, unlike the corals surrounding it.

## Also known as

- **Hebrew:** אסציד שקוף
- **Russian:** Асцидия голубая

## Range

Red Sea

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