Microcosmus polymorphus

Microcosmus polymorphus is a sessile tunicate that can reach a maximum length of 15.0 cm. It is typically found in subtropical regions, specifically in the Atlantic and Mediterranean waters of Europe and the Northwest Pacific around Japan. This species attaches itself to various substrates, often in shallow waters, making it accessible to divers. Its appearance can be distinguished from similar species by its unique shape and texture, which may vary in coloration depending on the environment it inhabits. The tunicate's body is covered in a tough outer layer, and it is often found in colonies, which can make identification easier for divers observing multiple individuals together. Microcosmus polymorphus is hermaphroditic, meaning it possesses both male and female reproductive organs. It reproduces through both cross-fertilization and self-fertilization, with fertilized eggs developing into lecithotrophic larvae before settling down and metamorphosing into benthic adults. This life cycle allows for a wide distribution of the species across its habitat. Encounters with Microcosmus polymorphus during dives can be quite common, as it has been recorded at various dive sites. Divers may observe it clinging to rocks or other hard surfaces, often in groups. While it does not pose any threat to humans, its presence contributes to the biodiversity of marine ecosystems. Currently, the conservation status of this species is not evaluated, and it is not listed under any specific protections.