Tube-dwellarsNot all tube dwellars are sedentary polychaetes. Majority of the tube dwellars are sedentary tubiculous polychaetes that are highly specialized for such existence. Members of the Family Maldanidae family live anterior end downward in their tubes and have parapodia reduced to ridges to give a cane joint appearance.Errant carnivorous families like the members from the families Onuphidae and Eunicidae are tubiculous and extend from the opening to seize passing prey. They have well developed prostomial sensory appendages. Their parapodia which are not markedly reduced are used for crawling around the heavy conspicous membranous tubes. The tubes of the onuphids and maldanids occur in great numbers in intertidal regions. The onuphids cover their tubes with shells, seaweed and other debris the worm collects and places in position with its jaws. Like the maldanids, the sabellariids and pectinariids construct sand-grain tubes. When the water is turbulent, the Sabellariids build tubes on top of each other creating honey-comb aggregations. Such colonies are composed of millions of individuals assuming reeflike proportions.
The pectinariids build cone shaped tubes with the smaller end opening at the surface. The oweniids build their tubes out of flat shell fragments. The free edge of the fragment is directed upwards and anchor the tube in the substratum. Being flexible, the tube changes shape like a loose-fitting cuticle as the worm moves. The fan worms, Sabellids construct their tubes out of sand grains embedded in mucus.
The arenicolids and the terebellids are sedentary tube dwellars.
They grip the sides of their tubes tightly with their uncini Functions of the tube:
The tubes are composed of secreted material or sand grains cemented together or a combination of secreted and foreign material. Tube secretions are commonly produced by the glands on the ventral surfaces of the segments. Here are some of the following types of tubes made by the different families of polychaetes.
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