Oyster Thief, Colpomenia sinuosa

Oyster Thief, Colpomenia sinuosa. Algae photographed in it’s native environment within Bahía San Francisco, Guaymus, Sonora, January 2026. Photograph and identification  courtesy of Dr. Jake Turin,  Albuquerque, New Mexico.

Phylogeny:  The Oyster Thief, Colpomenia sinuoa (Mertens ex Roth) Derbès & Solier, 1851), is a member of the Scytosiphonaceae Family of Brown Algae. The Colpomenia Genus is one of twenty-nine genera in the Scytosiphonaceae Family, and there are eleven species in the Colpomenia Genus. They are also known as the Brown Slimy Glob, the Puffy Brown Seaweed and Sinuous Ballweed and in Mexico as Cerebro de Mar.

Morphology: Oyster Thieves have an odd lumpy beige to yellowish-brown body and form clumps that are up to 1.0 m (3 feet 3 inches) in diameter. They have a hollow body that is covered with fine hairs and can reach between 2.0 cm (0.8 inches) and 8.0 cm (3.1 inches) in diameter. They have a crisp outer membrane with a smooth somewhat shiny texture, encasing a hollow interior. They start growing as a single rounded blob and with maturity they form sheets with irregular wrinkled blobs or puffed up lobes.

Habitat and Distribution:  The Oyster Thief is found in protected marine environments attached to algae, coral rubble and rocks with water temperatures between 15°C (59°F) and 26°C (79°F ) at depths up to 37 m (120 feet).  They are most abundunt in the spring and summer but are also present year round. The Oyster Thief is found in all Mexican waters of the Pacific Ocean.

Diet: The Oyster Thief possesses zooxanthellae that use photosynthesis to create food (amino acids, fats, sugars) from sunlight, water and coral waste carbon dioxide.

Reproduction: The Oyster Thief is poorly studied and their method of reproduction has not been documented.

Conservation:  From a conservation perspective the Oyster Thief has not been formally evaluated. They are utilized as a human food and as animal feed. They are of interest to the scientific community due to their high genetic diversity found within the species cosmopolitan distribution in the world’s oceans. They are also a source of Colpol, that represents a new class of compounds that are currently being evaluated for their antibacterial and antitumor properties. The Oyster Thief is not suitable for use in aquarium environments.

Synonyms:  Colpomenia sinuosa f. typica, Stilophora sinuosa and Ulva sinuosa.