Spirorbis

Spirorbis is a genus of small, tube-dwelling, marine polychaete worms belonging to the family Serpulidae. These worms are characterized by their distinctive, coiled, calcareous tubes which they secrete and inhabit throughout their lives. These tubes are typically white or pale in color and range in size from a few millimeters to a centimeter in diameter, depending on the species and environmental conditions.

Spirorbis are commonly found attached to various hard substrates in intertidal and subtidal zones. These substrates can include rocks, seaweed, shells, pilings, and even the exoskeletons of marine invertebrates such as crustaceans. They are cosmopolitan in distribution, found in oceans worldwide, with different species exhibiting preferences for specific geographic locations and environmental conditions, such as salinity and water temperature.

These sessile worms are filter feeders, extending their feathery branchial crown, or radioles, from the opening of their tube to capture plankton and other suspended organic matter from the surrounding water. When disturbed, they quickly retract their radioles back into the tube for protection.

Reproduction in Spirorbis can occur through both sexual and asexual means. Sexual reproduction involves the release of gametes into the water column, where fertilization occurs. Asexual reproduction, such as budding, can also occur in some species, allowing for rapid colonization of suitable habitats.

Spirorbis species play an important role in marine ecosystems as both filter feeders and as a source of food for other marine organisms. They are also useful as bioindicators of environmental pollution, as their presence or absence, and the condition of their tubes, can reflect water quality and the presence of contaminants.