Tough Didemnid

Didemnum coriaceum

Didemnum coriaceum is a sessile tunicate that typically forms dense colonies. It has a tough, leathery texture, which gives it its common name. The colonies can vary in color, often appearing in shades of brown or yellow, and can be distinguished from similar species by their robust consistency and the way they cluster together. This species is commonly found in temperate marine environments, thriving in shallow waters, particularly in depths shallower than 40 meters, with 90% of recorded occurrences at depths shallower than about 30 meters. This species primarily inhabits rocky substrates and can be found on various marine structures, including piers and jetties. As a filter feeder, it consumes plankton and organic matter from the water column. Didemnum coriaceum is hermaphroditic, allowing for both cross- and self-fertilization during reproduction. The life cycle begins with eggs developing into lecithotrophic larvae, which eventually settle and metamorphose into benthic adults. Encounters with Didemnum coriaceum during dives can be quite common, as it has been recorded at numerous dive sites. Divers may observe its colonies covering surfaces, providing a unique habitat for small marine organisms. While the conservation status of this species has not been evaluated, it is important for divers to be aware of their presence and the ecological role they play in their environments.