---
title: Pikachu Nudibranch (Thecacera pacifica)
scientific_name: Thecacera pacifica
common_name: Pikachu Nudibranch
taxon: Nudibranch
published: 2024-05-06T15:22:24.526Z
updated: 2026-08-12T08:16:28.467Z
tags: Pikachu Nudibranch, Thecacera pacifica, Nudibranch, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/pikachu-nudibranch
---

# Pikachu Nudibranch (*Thecacera pacifica*)

## Quick facts

- **Group:** Nudibranch (*Nudibranchia*)
- **Size:** up to 5 cm
- **Depth:** 3-30 m
- **Diet:** Carnivore
- **Activity:** Cathemeral
- **Rarity:** Rare
- **Habitat:** Rubble and silty slopes where bryozoans grow
- **Reproduction:** Egg layer, Simultaneous hermaphrodite

## How to recognise it

- bright orange body with round black spots and blue at the base of each appendage
- two black-tipped rhinophores standing up like ears
- a pair of raised lobes flanking the gills at the rear
- length up to 5 cm

Bright orange, spotted black, with two black-tipped rhinophores standing up at the front and a pair of raised lobes at the back. The resemblance to a cartoon mouse is close enough that the nickname has effectively replaced the scientific name, and dive guides sell trips on it.

Underneath the marketing it is a bryozoan specialist. Those lobes flanking the gills are extensions of the mantle that protect the gill plume, and the animal grazes the fine encrusting colonies growing on rubble and dead coral - not corals, not sponges, but the thin lacy mats most divers never look at twice.

The color is a warning rather than a costume. A soft-bodied animal that crawls in the open in daylight is advertising, and chromodorid-style aposematism works even when the chemistry behind it has not been analyzed.

It is uncommon, small and easy to miss, and its distribution is genuinely patchy - a site can produce several in a week and then none for a year, which tracks the boom and bust of the bryozoan colonies it depends on.

## Also known as

- **English:** Pikachu Longhorn Dorid, Orange Sea Slug, Pikachu Sea Slug
- **German:** Pazifische Thecacera
- **Portuguese:** Lesma-do-mar-do-Pacífico
- **Japanese:** ウデフリツノザヤウミウシ
- **Chinese:** 太平洋多角海牛
- **Russian:** Пикачу

## Scientific synonyms

- *Ohola pacifica* Bergh, 1884
- *Thecacera inhacae* MacNae, 1958

## Range

Gulf of Mexico, Indian Ocean, Mozambique

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/pikachu-nudibranch)*
*Updated: August 12, 2026*