Purple-lined Nembrotha

Overview

The Purple-lined Nembrotha (Nembrotha purpureolineata) is a vibrant, large dorid nudibranch found throughout the tropical Indo-West Pacific. It is well-known for its striking, variable coloration and is often observed in reef environments where it feeds on ascidians.

Distribution & habitat

This species is widely distributed across the tropical Indo-West Pacific, ranging from Western and eastern Australia to southern Japan. It is typically found in reef habitats, including external reef zones and reef flats, often frequenting areas with sand and rubble.

Appearance

This nudibranch features a creamy white or yellowish body, though much of the base color is often obscured by large, dark brown or reddish-brown patches and longitudinal stripes. A defining characteristic is the blue-to-purple edging found on the foot, oral tentacles, and sometimes the rhinophore sheaths. It possesses vermilion-colored rhinophores and gills, which add to its vivid appearance. Individuals can grow up to 120 mm in length and are sometimes confused with similar species like N. lineolata or N. aurea.

Biology & behavior

Like other nudibranchs, this species is a hermaphrodite. It is known to be poisonous, utilizing defensive chemicals derived from its diet of sea squirts (ascidians) to deter predators. When disturbed, it can excrete a deep blue slime containing these defensive compounds. Mating often occurs in a head-to-tail position, and individuals have been observed continuing to feed on ascidians while mating.