SiboglinidaeTubeworms

Siboglinidae is a family of marine annelid worms. These unique invertebrates are commonly known as beard worms or, more scientifically, as siboglinid tubeworms. They are characterized by their sessile lifestyle, living within tubes they secrete. A defining feature of many siboglinid species is the absence of a digestive system, including a mouth and anus, in their adult form. Instead, they rely on a symbiotic relationship with chemosynthetic bacteria housed within a specialized organ called the trophosome. These bacteria metabolize chemicals, such as hydrogen sulfide, from their environment, providing the worm with nourishment.

Siboglinid tubeworms are found in a variety of marine habitats, often in extreme environments. They are particularly well-known for their presence around deep-sea hydrothermal vents and cold seeps, where they thrive in the chemically rich waters. Some species also inhabit shallow-water sediments. They possess a crown of tentacles, often described as a "beard," which are responsible for absorbing dissolved oxygen and nutrients from the surrounding water and for exchanging gases. Reproduction in siboglinids is typically sexual, with external fertilization being common. Their ecological role is significant, particularly in deep-sea ecosystems, where they form the base of food webs through their symbiotic relationships.