Umbrella Slug

Overview

The Umbrella Slug (Umbraculum umbraculum) is a distinctive marine gastropod recognized by its large, circular body and a relatively small, flattened shell perched on its back. Unlike many other sea slugs, it maintains a rigid, non-elongated shape while moving, with its head position marked by a pair of tubular, rolled rhinophores.

Appearance

This mollusc features a pustule-covered mantle that typically ranges in color from yellow and beige to vibrant orange. The dorsal shell is a flattish, cone-shaped structure that is often obscured by encrusting organisms like algae or small tube worms. Beneath the shell, the animal possesses bipinnate gills on its right side, which may be extended when the slug feels secure.

Distribution & habitat

Widely distributed across tropical and warm temperate waters, this species is found in the Indo-Pacific, Atlantic, and Mediterranean regions. It inhabits various environments, including rocky shores, sandy-muddy bottoms, and occasionally seagrass beds, ranging from the low intertidal zone to depths of over 200 meters.

Biology & behavior

Umbrella Slugs are specialized sponge feeders. They lack an eversible proboscis, so they feed by opening a mid-anterior cleft at the base of their head to press their mouth directly against a sponge, rasping the surface with a broad radula. They are often well-camouflaged, blending into the sponges they consume or the surrounding substrate.

Reproduction

During reproduction, these slugs produce a long, coiled ribbon containing millions of eggs, which eventually hatch into planktonic larvae.