Trochophore larva of the polychaete Serpula

On 26 April 2010, I fertilized eggs of the polychaete Serpula columbiana (red tube worm) from adults collected from the floating docks in Charleston, OR marina. These polychaete annelids live in calcareous coiled tubes and have a red plume of radioles (feathery tentacles) that aids in suspension and filter feeding. As with many other polychaetes, top-shaped trochophore larva is the first swimming stage. These trochophore larvae live in the plankton, and eventually settle and metamorphose into the adult worm. The trochophore larva is characterized by the presence of the prototroch, a preoral band of cilia, which beat rapidly to propell the larva through the water. These pictures show a 21-day-old trochophore larva of Serpula columbiana. The prototroch is clearly seen around the widest part of the larva. The apical tuft of cilia, located at the anterior end is partially in focus on the bottom photo (at about 8 o'clock). In the lateral view, the mouth is seen near the top and between the prototroch and metatroch (another circumferential band of cilia posterior to the mouth). The mouth leads to a heavily ciliated gut (brown in the photo). See pictures of a later developmental stage of this species.