Sargassum muticum is a brown seaweed, it is an invasive species also known as Japanese Wireweed, from the northern Pacific Ocean and now distributed throughout Europe. It can produce sexually and asexually and normally it reaches the sexual maturity in the summer, by the time gamete production takes place in the receptacles. It is fixed by a basal disc, from which it develops. In its branches there are aerocysts that keep the algae upright in the water and allow them to float. The color depends on the time of year, varying from deep brown to yellowish brown.