Mauritius Neon Slug.

Tambja morosa, also known as Tambja kushimotoensis, is a species of sea slug, a dorid nudibranch, a shell-less marine opisthobranch gastropod mollusk in the subfamily Nembrothinae within the family Polyceridae, itself belonging to the clade Orthogastropoda within the clade Nudipleura.
It is also sometimes placed in the family Gymnodorididae.

Distribution

This species has a primarily Indo-Pacific distribution, and is found in Philippines, Indonesia, Thailand, Myanmar, Malaysia, New Zealand, Solomon Islands, Taiwan, Australia, French Polynesia and Fiji.

Description
This large species of Tambja grows to approximately 70-75 mm in length. Although dark green specimens are found in the cooler waters of New South Wales and northern New Zealand, this species is normally black with blue markings. The skin of this slug is wrinkled, and appears nearly black underwater. It has a approximately five round, blue spots on its back, a blue band around its head, and a bright blue margin.

Diet
Tambja morosa feeds on arborescent bryozoan colonies.