About Cratena peregrina (Gmelin, 1791)
Cratena peregrina, commonly called the pilgrim hervia, is an aeolid sea slug. It reaches an average size of 3 to 5 centimeters. Its body is thin and slender, ending in a long, sharply pointed tail. The base body color is milky white, and it has 8 to 10 clusters of dorsal cerata, which can be bright red, purple, brown or blue, with distinctly luminescent blue tips. These cerata function like gills, and each one holds a terminal outgrowth of the digestive gland called a diverticulum. Its head matches the milky white body color, and bears a pair of bright orange rhinophores, plus two long, whitish buccal tentacles that resemble horns. This species is found in the Mediterranean Sea and the eastern Atlantic Ocean, ranging from the English Channel south to Senegal. It inhabits rocky bottoms and slopes in clear, well-oxygenated water, at depths between 5 and 50 meters.
