51.2 Saturday, Jan. 5 Mechanisms of Metamorphic Remodeling in Hydroides elegans (Polychaeta). SHIPLEY, M.S.; PATZ, K.S.; NEDVED, B.T.; HADFIELD, M.G.*; University of Hawaii at Manoa; University of Hawaii at Manoa; University of Hawaii at Manoa; University of Hawaii at Manoa firstname.lastname@example.org
Larvae of the serpulid polychaete Hydroides elegans are competent to settle and metamorphose five days after fertilization. At that stage, they are classical 3-setiger nectochaete larvae that are propelled by a well developed ciliary prototroch that also provides their filiter-feeding current. On contact with an appropriate bacterial biofilm, the larvae transform into a tube-dwelling, tentacle-feeding juveniles within 10 hrs. During the process, ciliated trochal bands and apical sensory organ disappear, the mouth is relocated from a ventral to an anterior-terminal position, and the feeding tentacles differentiate and elongate. We employed laser-scanning confocal microscopy and (1) acridine orange and TUNEL labeling to detect cell-death processes, and (2) Click-iT EdU labeling to detect cell proliferation, during and following metamorphosis in larvae of H. elegans. Apoptosis accounts for the loss of the prototroch and metatroch cells, the apical sensory organ and large numbers of epidermal cells on the larval episphere, especially at the anterior tip of the larva where the mouth will be positioned. Rapid cell proliferation produces the tentacles. After the tentacles are sufficiently developed for feeding, groups of apparent stem cells remain at their bases to accomplish tentacle elongation as the worm grows.