---
title: Starback Tentacled Dorid (Asteronotus cespitosus)
scientific_name: Asteronotus cespitosus
common_name: Starback Tentacled Dorid
taxon: Nudibranch
published: 2026-08-25T15:20:34.629Z
updated: 2026-08-25T15:48:40.664Z
tags: Starback Tentacled Dorid, Asteronotus cespitosus, Nudibranch, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/starback-tentacled-dorid
---

# Starback Tentacled Dorid (*Asteronotus cespitosus*)

## Quick facts

- **Group:** Nudibranch (*Nudibranchia*)
- **Size:** up to 40 cm
- **Diet:** Spongivore
- **Activity:** Nocturnal
- **Rarity:** Rare
- **Habitat:** Under large rocks by day, on open rock at night
- **Reproduction:** Simultaneous hermaphrodite, Egg layer
- **Hazard:** Poisonous

## How to recognise it

- enormous for a sea slug, recorded to 40 cm
- yellowish to brown, with large tubercles arranged in rings
- under big rocks in daylight, out after dark
- juveniles far more strongly patterned than adults

Forty centimeters. This is the largest sea slug in the catalogue and one of the largest anywhere, and almost nobody has seen one.

The reason is the schedule. It spends daylight wedged under a large rock or slab and comes out onto open surfaces after dark, so a reef can hold several without a single day diver ever meeting one. What you find at night is a heavy yellowish to brown animal with big tubercles arranged in rings across the back, moving slowly over sponge-covered rock.

Size on that scale changes what the animal is doing. A forty-centimeter slug is not hiding from anything small, it is simply too large to be worth attacking, and the chemistry it takes from sponges makes the point again. Very large sea slugs are almost always nocturnal sponge feeders for the same reasons: sponges are an unlimited food nobody competes for, and the size that comes with eating them is only affordable if you do not need to be quick.

Juveniles look like a different species, patterned far more strongly than the adults, which is worth knowing because a young one and a full-grown one on the same reef will not read as the same animal.

On a night dive over rubble and rock, this is the thing to hope for.

## Also known as

- **English:** Starback Tentacled Dorid, Clumpy Nudibranch
- **French:** Astéronotus verruqueux
- **Japanese:** コバンウミウシ
- **Chinese:** 草皮星背海蛞蝓
- **Russian:** Астеронотус дерновый
- **TH:** ทากเปลือยขรุขระ

## Scientific synonyms

- *Asteronotus brassica* J. K. Allan, 1932
- *Asteronotus fuscus* O'Donoghue, 1924
- *Asteronotus hemprichi* Ehrenberg, 1831
- *Asteronotus mabilla* (Abraham, 1877)
- *Asteronotus wardianus* J. K. Allan, 1932
- *Doris cespitosus* van Hasselt, 1824
- *Doris mabilla* Abraham, 1877
- *Jorunna marchadi* Risbec, 1956

## Range

Madagascar, Mozambique

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/starback-tentacled-dorid)*
*Updated: August 25, 2026*