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 sinuosa (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. In Mexico they are called Cerebro de Mar. The genus name Colpomenia comes from the Greek word meaning “pouch” or “purse” and refers to the hollow, inflated, thallus. The species name sinuosa comes from Latin and means “full of bends”, “winding”, or “sinuous”. This refers to the wavy, wrinkled, surface of mature specimens.
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 (thallus) 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. Between the outer membrane and the interior are medullary cells. 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, shells, and rocks with water temperatures between 15°C (59°F) and 26°C (79°F ). They live in the intertidal zone and at depths up to 37 m (120 feet). They are most abundant in the spring and summer but are also present year round. The Oyster Thief is found worldwide in temperate to tropical seas. They are found in all Mexican waters of the Pacific and Atlantic Oceans.
Diet: The Oyster Thief use chlorophyll A and C to conduct photosynthesis to create food (amino acids, fats, sugars) from sunlight, water and coral waste carbon dioxide. Photosynthesis also provides the oxygen to fill the thallus.
Predation: The Oyster Thief is prey for generalist herbivores such as sea urchins, fish, and sea stars.
Reproduction: The Oyster Thief has a complex, heteromorphic life history alternating between visible erect bubble-like gametophytes and microscopic prostrate, filamentous sporophytes. Sexual reproduction occurs when anisogamous gametes fuse to form zygotes. The zygotes gave rise to new sporophytes. Asexually occurs through plurispores and parthenogenesis.
Ecosystem Interactions: The Oyster Thief provides shelter and structure for various species of crustaceans, fish, mollusks, and other invertebrates.
Human Interactions: The Oyster Thief can have a negative impact on bivalve fisheries in that if they attach to a small bivalve their buoyancy can sometimes float the shell and carry it away. 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. From a conservation perspective the Oyster Thief has not been formally evaluated.
Synonyms: Colpomenia sinuosa f. typica, Stilophora sinuosa and Ulva sinuosa.