Elysia timida, also known as the Green Elysia, is a sacoglossan sea slug native to the Mediterranean Sea. This marine opisthobranch gastropod mollusk is also found in the eastern Atlantic Ocean and the Caribbean Sea. It belongs to the family Plakobranchidae and is sometimes referred to by its synonyms, Elysia viridis and Notarchus timidus.
Identifying Elysia timida is relatively easy due to its distinctive characteristics. This sea slug has a maximum length of 10 mm and a width of 1.3 to 1.4 mm. The parapodia are low with a few higher projections, giving it a hunch-backed appearance when viewed from the side. There is a tiny protuberance on the first projection of the left parapodium that fits into a small groove on the right parapodium’s first projection. The slug’s body is chalk white with a few vermilion dots, and the bright green branches of the liver are visible through the sides, inner parapodia, and back.
Elysia timida has several distinct characteristics. Its body is predominantly chalk white adorned with vermilion dots. The green liver branches are visible through its semi-transparent body parts. The foot is divided by a transverse furrow, and the rhinophores are thick and rolled up. The parapodia feature a few higher projections, contributing to its unique silhouette.
Elysia timida primarily inhabits shallow, sunlit waters, living epifaunally on algae and rocks. It is usually found on Acetabularia acetabulum during warmer months and Padina pavonia during cooler months. This species can consume only young, pre-calcified stalks of A. acetabulum. Remarkably, Elysia timida retains functional symbiotic chloroplasts from its food, allowing it to continue photosynthesis within its tissues. It has a short planktonic lecithotrophic larval phase when algae are scarce and a direct, non-planktonic developmental mode with intracapsular metamorphosis when food is abundant.
An intriguing fact about Elysia timida is its ability to produce a defensive secretion that deters predatory fish such as the ornate wrasse (Thalassoma pavo). This secretion makes it an unappealing target for predators, enhancing its survival in the wild.
Malta offers excellent diving spots for divers to observe Elysia timida in its natural habitat. Some of the best sites to spot these sea slugs include:
Reqqa Point – Located on Gozo’s north coast, this site provides a rich environment for Elysia timida, especially in shallow waters where algae grow abundantly.
Cirkewwa – On Malta’s northern tip, Cirkewwa is known for its clear waters and diverse marine life, making it an ideal spot to find Elysia timida.
Hondoq Bay – Situated on Gozo’s southeast coast, this area is popular for its rocky substrates and algae, attracting these unique sea slugs.
Diving at these locations, particularly during the warm months when algae are more prevalent, increases the chances of encountering the beautiful and fascinating Elysia timida.
