---
title: Black-horned Egg-eater (Favorinus tsuruganus)
scientific_name: Favorinus tsuruganus
common_name: Black-horned Egg-eater
taxon: Nudibranch
published: 2026-08-27T11:01:03.219Z
updated: 2026-08-27T11:25:13.056Z
tags: Black-horned Egg-eater, Favorinus tsuruganus, Nudibranch, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/black-horned-egg-eater
---

# Black-horned Egg-eater (*Favorinus tsuruganus*)

## Quick facts

- **Group:** Nudibranch (*Nudibranchia*)
- **Size:** up to 3 cm
- **Diet:** Molluscivore
- **Activity:** Cathemeral
- **Rarity:** Uncommon
- **Habitat:** Reef and rubble, on the egg ribbons of other sea slugs
- **Reproduction:** Simultaneous hermaphrodite, Egg layer

## How to recognise it

- cerata tipped black, which the other egg-eater here does not have
- rhinophores carrying three swellings rather than two
- three centimeters, larger than most of the genus
- sitting on a coiled egg ribbon rather than on sponge or coral

Start with the horns, because they place the genus before anything else does. Every aeolid has a pair of rhinophores standing up at the front; on Favorinus they are strung with swellings along their length, like beads on a cord, and nothing else on this reef carries that shape.

What the genus does is eat eggs. Sea slugs lay their spawn as coiled ribbons stuck to rock or sponge, thousands of embryos in a rope of jelly, abandoned in the open with no parent anywhere near, and these animals specialize in exactly that. It is food that never has to be chased and never fights back, and it comes with a consequence: an egg ribbon contains no stinging cells, so unlike almost every other aeolid these come away from a meal completely unarmed.

That also gives you the search method. You do not look for the slug. You look for spawn, and then you look at the spawn closely.

This species is the black-tipped one. The cerata carry dark apices, and the rhinophores have three swellings rather than the two or three of its relative here, whose cerata instead change color to match whichever eggs it has been eating. At three centimeters (1.2 in) this is also the larger of the two.

It was described in 1964 by Kikutaro Baba, who spent six decades working through the sea slugs of Japan and whose name sits on a startling number of the animals in this section.

## Also known as

- **English:** Black-horned Egg-eater
- **Portuguese:** Lesma-do-mar-peluda-de-pontas-pretas
- **Japanese:** ツルガチゴミノウミウシ
- **Chinese:** 敦賀灰翼海蛞蝓
- **Russian:** Фаворинус цуруганский

## Range

Japanese part of the Japan Sea, Mozambique, New Zealand, South Africa

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/black-horned-egg-eater)*
*Updated: August 27, 2026*