Comprehensive DescriptionRead full entry
The radioles of members of Family Sabellidae contain a food groove with a stepped cross-section that serves as a size-filter. The smallest particles, which fit in all the way to the bottom of the groove, are usually eaten. Moderate size particles, in the upper parts of the groove, are often glued together to build the tube. The largest particles, too large to fit within the groove, are usually rejected. The radioles are also used for gas exchange (like gills) but the circulatory pattern within them is unusual. Instead of having afferent and efferent vessels, the radioles have a single branchial vessel in each radiole which the blood flows in and out of. Sabellids possess giant nerve fibers running down their body which allows them to retract rapidly into their tube if disturbed.