Gem Sea Slug

Goniobranchus geminus is a species of very colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.

Taxonomic history

Until 2012 this species was known as Chromodoris geminus but was moved to the genus Goniobranchus as a result of a molecular (DNA) study.

Description

It can reach a maximum size of 5 cm in length. It has four distinctive coloured lines around the mantle edge. Starting from a thin white outer line, then a light grayish line, followed by another white line and finally a bright golden yellow line. The background coloration from the back is light brown to yellowish speckled with mauve ocelli circled with a white margin. The foot, clearer and with a white margin, also has ocelli. The rhinophores are yellow or purple and laminated, gills are white outlined with beige.

Distribution & habitat

This sea slug lives in the Indian Ocean from Kenya to Sri Lanka and in the Red Sea and has a predilection for the external slopes of coral reefs.

Similar species

• Goniobranchus kuniei (Pruvot-Fol, 1930).
• Chromodoris leopardus (Rudman, 1987).
• Risbecia tryoni (Garrett, 1873).
• Chromodoris tritos (Yonow, 1994).