Didemne Jaune

Overview

Polysyncraton bilobatum is a colonial tunicate, often referred to as the "Didemne jaune" in French. It forms thin, leathery, encrusting colonies that typically appear as small patches on various marine substrates.

Appearance

These colonies are generally thin, measuring only 1 to 3 mm in thickness, though they can spread over significant surface areas. While classically yellow-orange, their coloration is variable and may range from white and pale yellow to beige or bright orange. The surface of the colony is characterized by regularly spaced, star-shaped inhalant siphons, each featuring six small lobes or languets. The overall texture is smooth and leathery, and the colony is opaque, which helps distinguish it from more translucent species.

Distribution & habitat

This species is found in the Mediterranean Sea and the eastern Atlantic, with a range extending from the British Isles and Brittany down to the coasts of Morocco, Senegal, and South Africa. It inhabits a variety of environments, including rocky reefs, seagrass beds, and sedimentary zones. It is typically found attached to solid substrates or the base of seagrass, ranging from the low-tide level down to depths of approximately 100 meters.

Biology & behavior

As a filter-feeding organism, it captures microscopic planktonic particles from the water column by generating a constant internal water current. The colony is hermaphroditic and reproduces both sexually and asexually through budding. In sexual reproduction, fertilized eggs are often brooded within the colony's common cloacal cavity before being released as free-swimming larvae that eventually settle to form new colonies.