Ascidie Petit Monde

Overview

Pyura microcosmus is a solitary sea squirt characterized by a tough, leathery, and wrinkled outer tunic. Often appearing as a "dirty" or camouflaged mass due to attached debris and epibionts, this small tunicate is a common inhabitant of sheltered marine environments in warm temperate waters.

Appearance

This species typically reaches a size of 3 to 4 cm, though some populations may grow up to 5 cm. Its body is ovoid and covered in a thick, leathery tunic that remains wrinkled even when the animal is fully expanded. The tunic color ranges from yellowish-brown to reddish or purplish-brown. A key identifying feature is its two siphons, which are well-separated and marked with longitudinal red and white stripes, particularly visible on their inner surfaces. These siphons are sensitive to light and disturbance, causing them to contract quickly when the animal is inspected.

Distribution & habitat

Pyura microcosmus is found in the northeastern Atlantic, the Mediterranean Sea, and the Red Sea. It prefers shallow, sheltered areas where it attaches to hard substrates such as rocks, stones, shells, and occasionally man-made structures. It is frequently observed in the infralittoral zone and is known to be a component of certain benthic communities, such as horse mussel beds.

Biology & behavior

As a filter feeder, this tunicate draws in seawater through its oral siphon to capture plankton and other microorganisms, expelling filtered water through its atrial siphon. It is a sessile organism that lives attached to the seabed as an adult. While it can be found individually, it is often obscured by various plants and animals that grow on its surface, providing effective camouflage.