---
title: Katalexis Mexichromis (Mexichromis katalexis)
scientific_name: Mexichromis katalexis
common_name: Katalexis Mexichromis
taxon: Nudibranch
published: 2024-05-08T10:54:14.179Z
updated: 2026-08-14T13:48:26.002Z
tags: Katalexis Mexichromis, Mexichromis katalexis, Nudibranch, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/katalexis-mexichromis
---

# Katalexis Mexichromis (*Mexichromis katalexis*)

## Quick facts

- **Group:** Nudibranch (*Nudibranchia*)
- **Size:** up to 2 cm
- **Depth:** 3-30 m
- **Diet:** Spongivore
- **Activity:** Diurnal
- **Rarity:** Uncommon
- **Habitat:** Sponge-covered rock and rubble on reef slopes
- **Reproduction:** Egg layer, Simultaneous hermaphrodite
- **Hazard:** Poisonous

## How to recognise it

- small white slug with a purple-blue mantle margin and yellow spots
- low ridge running down the middle of the back
- purple rhinophores and gill tips
- length up to 2 cm

Two centimeters (0.8 in) of white slug edged in purple and spotted in yellow, small enough that most divers pass over it and macro photographers do not.

It was named in 2001, from material collected in this sea, by Nathalie Yonow - whose work on the sea slugs of the Red Sea is the reason a good part of this section of the catalogue can be identified at all. Naming a species is not a historical activity: a great many of the small animals on these reefs were described within living memory, and some of the ones a diver photographs this year still have no name.

Like the rest of the chromodorids it lives on sponges and keeps their chemistry for its own defense, concentrated around the mantle rim. The bright margin is the label.

Finding one is a matter of working slowly over sponge-covered rock with a torch. At this size the color is the only thing that carries, and in white torchlight the purple edge is what catches the eye first.

## Also known as

- **French:** Mexichromis à papilles violettes

## Range

Banda Sea

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/nudibranch/katalexis-mexichromis)*
*Updated: August 14, 2026*