TUBE-BUILDING AND FEEDING IN THE CHAETOPTERID POLYCHAETE, SPIOCHAETOPTERUS OCULATUS

¹ Department of Biology, Gettysburg College, Gettysburg, Pennsylvania

1.Spiochaetopterus oculatus secretes a small, cornified, annulated tube, approximately 0.75 mm. in diameter and eight or more centimeters in length. The tube is constructed vertically in intertidal or subtidal sand and mud with only a few millimeters of the upper end of the tube projecting above the surface of the substratum.

2. The tube is secreted by epidermal glands occupying almost the entire convex ventral surface of the anterior body region.

3. One vertical half-cylinder of tube is secreted at a time, the length of the cylinder corresponding to a section between annulations. The wall is gradually thickened with additional secretions.

4. Temporary, transverse, button-like partitions are constructed in the lower part of the tube. The partitions are perforated by several openings.

5. An entire new lower region of tube may be constructed as a branch of the old tube. The lower part of the old tube is then sealed off.

6. In constructing such a branch, the old tube wall is cut open with one of a pair of greatly enlarged blade-like setae of the fourth segment. These setae are also used to remove the temporary tube partitions.

7. The water current through the tube is produced by the beating of membranelles which line three ring-like openings formed by the foliaceous notopodia of each segment in the middle region of the body.

8. The mid-dorsal ring of each of the first 13 or so foliaceous notopodia secretes a mucous bag which strains out fine detritus and plankton from the water current passing through the tube. The mucous bag is caught and rolled up as a food ball by a cupule located behind each ring. The food ball is then passed forward to the mouth along a ciliated mid-dorsal groove which runs anteriorly from the posterior tip of the body.

9. The greatly elongated palps function chiefly to remove feces and also to remove over-large masses of detritus which enter the tube with the water current.