Radiole Regeneration and Branchial Crown Structure of the Feather Duster Worm, Schizobranchia insignis

Abstract

The annelid feather duster worm, Schizobranchia insignis, is an abundant marine invertebrate found subtidally and in the low intertidal of the northeastern Pacific Ocean. The Phylum Annelida is frequently utilized as a model of regeneration due to the pronounced array observed. The main purpose of this study was to examine the radiole regeneration of S. insignis and to perform a branchial crown survey of the understudied species. Previous research has examined the regeneration of the entire posterior and anterior region of the worm; however, limited information is available on the regeneration of radioles, the anterior appendages used for feeding and respiration. By cutting radioles of S. insignis and observing the patterns of regeneration, I identified twelve distinctive morphological stages (A-L) with detailed descriptions of the external and internal features. The radiole regeneration of Eudistylia vancouveri, a species from a closely related genus of S. insignis, was also examined and found to have a less complex, non-branching regrowth process. During the radiole regeneration of S. insignis, the initiation of bifurcations is prioritized over the increase of internode length. The branchial crown of S. insignis exhibits a positive, non-linear power relationship between the number of radioles and drained body weight. Radioles of S. insignis with more bifurcations are generally longer and located more dorsally in the branchial crown. Lastly, the length of pinnules decreases as they travel distally on the radiole, unlike in other feather duster worm species. As the only sabellid with branched radioles, my study of S. insignis provides a unique look into appendage regrowth and branchial crown features.