Dusky Nembrotha

Overview

The Dusky Nembrotha (Nembrotha kubaryana) is a striking, large-bodied nudibranch known for its vivid and highly variable color patterns. Widely distributed across the tropical Indo-West Pacific, this sea slug is frequently observed on coral and rocky reefs where it associates closely with its primary food source.

Distribution & habitat

This species is found throughout the tropical Western Indo-Pacific, ranging from the Red Sea and East Africa through Southeast Asia to Oceania and Japanese waters. It typically inhabits coral and rocky reef environments, often found at depths between 3 and 55 meters.

Appearance

Reaching lengths of over 120 mm, the Dusky Nembrotha has an elongated, dark-colored body that is often black or dark violet. The surface is covered in pustules or ridges that are typically green, though some individuals may display orange or pinkish-orange markings. A key identifying feature is the vivid red-orange border often found along the margin of the foot, oral lappets, and rhinophore pockets. The rhinophores and gills can vary in color, appearing either green or red-orange depending on the specimen.

Feeding

This nudibranch is a specialized predator that feeds on colonial ascidians (tunicates), such as Sigillina and Atapozoa species. It is known to sequester chemical compounds from these prey, which it stores in its own tissues to use as a defensive mechanism.

Biology & behavior

When threatened, the Dusky Nembrotha can release a slimy mucus containing the toxins derived from its diet to deter predators. Like other dorid nudibranchs, it is a simultaneous hermaphrodite. During mating, individuals typically position themselves in a head-to-tail orientation to exchange gametes.