---
title: Tunicates (Tunicata)
scientific_name: Tunicata
common_name: Tunicates
rank: Subphylum
published: 2024-11-19T18:41:51.573Z
updated: 2026-08-23T21:14:21.446Z
tags: Tunicates, Tunicata, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/tunicates
---

# Tunicates (*Tunicata*)

## Quick facts

- **Rank:** Subphylum
- **Scientific name:** Tunicata
- **Body shape:** Invertebrate - Not a fish - coral, mollusc, crustacean, echinoderm and other invertebrate groups.
- **Subcategories:** 2

## How to recognise this group

- two distinct siphons for water intake and expulsion
- diverse forms: solitary, colonial mats, or amorphous masses
- sessile on hard substrates or free-drifting in water column

The bag of jelly stuck to the underside of that ledge is a closer relative of yours than anything else in this catalogue.

Tunicates are chordates, the same phylum as fish, frogs, birds and you. The adult hides it thoroughly, but the larva does not: a sea squirt hatches as something very like a tadpole, with a muscular swimming tail, a stiff rod running down its back called a notochord, and a nerve cord above it. Those are the defining features of the phylum you belong to, present for a few hours in an animal that will spend the rest of its life as a sac on a rock. Molecular work has since placed tunicates closer to the vertebrates than any other living group, which makes this the nearest branch of the tree to our own.

The name comes from the coat. Every one of them secretes a tunic around itself, leathery in some species and glass-clear in others, and the main structural material in it is cellulose, the stuff of paper and plant cell walls. Animals are not supposed to be able to make cellulose. This group is the exception, and it appears to have acquired the machinery early and kept it.

They live in two entirely different ways. Sea squirts cement themselves to hard bottom and never move again, either as single animals or as colonies of tiny individuals sharing one tunic. Salps and their relatives never touch the bottom at all, drifting through open water as transparent barrels that pump themselves along.

Both eat identically. Water enters through one siphon and leaves through the other, and in between it passes through a basket perforated with slits and coated in a sheet of mucus fine enough to catch bacteria. Those slits are the same structure as the gill slits of a fish, which is the other half of the family resemblance.


## Subcategories

- [Salps (Thaliacea)](https://redseacreatures.com/taxon/invertebrate/tunicates/salps)
- [Sea squirts (Ascidiacea)](https://redseacreatures.com/taxon/invertebrate/tunicates/sea-squirts)

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/tunicates)*
*Updated: August 23, 2026*