Seagrass Elysia

Elysia serca is a small, slender sea slug with a maximum length of 8 millimetres (0.31 in). The parapodia are less well developed than is the case in many other Elysia species and Elysia serca has a relatively large head. The characteristic radular teeth have the cusps bent at right angles to their bases. The base colour is some shade of brown or olive with many small patches of white and three larger white patches, two on the parapodia and one on the back near the heart.

Elysia serca is found in shallow waters in the western Atlantic from Florida south to Brazil. It was originally described from the southern end of its range, where it was found on brown algae and the green alga Ulva, on which it was presumably feeding. In Florida however it feeds on seagrasses including Halophila engelmannii, Halodule wrightii and Thalassia at depths of up to a few metres. Elysia catulus on the other hand, feeds on the seagrass Zostera and is found on the North American coast between South Carolina and Nova Scotia.