Lightbulb Sea Squirt

Overview

The Lightbulb Sea Squirt (Clavelina lepadiformis) is a colonial tunicate known for its distinct, transparent appearance that reveals its internal anatomy. These organisms typically grow in dense, bouquet-like clusters, with individual zooids connected by a common base called a stolon.

Appearance

Each zooid is shaped like a small, gelatinous club or bell, usually reaching up to 4 cm in length. The common name originates from the bright white, yellow, or occasionally pinkish rings and longitudinal lines that highlight the pharynx and internal structures against the clear body. These markings create a glowing, lightbulb-like effect that makes the species easily recognizable.

Distribution & habitat

Native to the northeastern Atlantic and the Mediterranean, this species is commonly found in shallow, sublittoral rocky environments, often attached to vertical walls, stones, shells, or algae. It is also frequently observed in artificial habitats such as marinas, docks, and vessel hulls, where it can be introduced via ship fouling. It thrives in a variety of light conditions and is known for its ability to tolerate different environmental settings.

Biology & behavior

Clavelina lepadiformis is an active suspension feeder, using a simple branchial basket to filter plankton and organic detritus from the water. It can reproduce both sexually and asexually. Asexual reproduction occurs through the stolon, allowing the colony to expand or regenerate. The species often follows an annual cycle, with growth beginning in early spring and larval production peaking in late summer, though some populations may persist year-round in sheltered areas like harbors.