Natural radiole damage and regeneration in the feather duster worm Schizobranchia insignis

Abstract

AbstractThe feather duster worm Schizobranchia insignis is an abundant marine annelid found subtidally and in the low intertidal of the northeastern Pacific Ocean. As in other sabellids, the anterior appendages, used for feeding and respiration, can be damaged by physical or biological means. Limited information is available on the regeneration of radioles leading us to study this process on a worm with radioles that dichotomously branch. First, we documented the occurrence of natural radiole damage in two populations of S. insignis found at environmentally distinct sites: a subtidal marina and an intertidal, rocky bench. All 21 worms collected from the exposed intertidal bench had branchial crown damage, whereas 15 of 22 worms (68%) sampled in the marina exhibited natural radiole damage. In the laboratory, we observed radiole regeneration on individuals of S. insignis from the marina by removing a single radiole. Radiole regrowth was a continuous process in which functionality was restored through radiole bifurcation, elongation, and the development of internal support structures. The regrowth of a single radiole of S. insignis took more than 35 days. However, in one of our studies, after 21 days, although not all individuals recovered, four of 12 worms (33%) had completed bifurcation. Pointed tips on the distal‐most branches signified the end of bifurcation. During recovery, individuals of S. insignis did not consistently regenerate the same number of branches observed prior to damage. In addition, a majority of the radiole elongation during recovery occurred after branching. The radiole regeneration in Eudistylia vancouveri, a closely related species found in the marina, was observed to compare regeneration in co‐occurring species. We found that the radiole regeneration in E. vancouveri was less complex because of the absence of branching. Since Schizobranchia is the only genus in which radioles are branched, our study of S. insignis provides a unique examination of natural radiole damage and regrowth.