- 1, 2) Sand worms ( Hermella ): 1) Tubes of Hermella alveolata with its inhabitants (2). 3) Shell tube worm ( Terebella emmalina )
The third group of tube worms is formed by the gillheads ( Cephalobranchiata ), so called, because the softened thread or tree-shaped appendages for breathing are at the head or at least at the anterior segments. They inhabit tubes from which they never emerge voluntarily. Accordingly, the appendages of most segments, except the anterior ones, are much less developed than those of the free-living many-bristles, and the way of life is more peaceful, as evidenced by the absence of dental plates in the oral cavity. - Twisted Lime worm ( Serpula contortuplicata )
In the Serpulacees ( Serpulacea ), the gills are located entirely at the front end of the body; the cilia that coat her cause a current to flow into the water, which supplies food to the mouth opening immediately below it. The head segment is not separated from the mouth segment, as is the case with most other Ringworms, but has grown together with it.