Meeting Abstract

P1-18   -   Neuroanatomical regeneration versus behavioral functionality of the rhinophores of the nudibranch mollusc Berghia stephanieae Watkins, KL*; Maroyan, A; Quinlan, PD; Tait, C; Katz, PS; University of Massachusetts, Amherst, MA ; University of Massachusetts, Amherst, MA ; University of Massachusetts, Amherst, MA ; University of Massachusetts, Amherst, MA ; University of Massachusetts, Amherst, MA klwatkin@umass.edu http://sites.google.com/a/umass.edu/katzlab/home

Many invertebrates are capable of impressive feats of regeneration following loss of body parts. Muscles and neurons can regenerate and reintegrate to regain functionality. We found that the chemosensory rhinophores of the nudibranch mollusc, Berghia stephanieae regenerate after being severed. In behavioral experiments, unmanipulated Berghia successfully navigated a T-maze in still water to localize a food source. However, they failed this test following removal of one or both rhinophores. Berghia that had just one rhinophore removed were able to successfully navigate the maze with their regenerated rhinophore five weeks after lesion. However, individuals that had had both removed were still unable to perform this task five weeks after lesion. We tracked the regeneration of the neurons and the muscles through five weeks post-removal. Immunohistochemical stains for serotonin and small cardioactive peptide showed the presence of dense arborization of fibers along the structure that closely tracked the regrowth of the rhinophore. Phalloidin staining of actin filaments showed that muscles were initially disorganized, but became organized and regrew with the regenerating rhinophore by one week after lesion. Neurobiotin fills of the rhinophore nerves showed that afferent axons had similar projections into the brain after five weeks of regeneration. However, these fiber tracts appear thinner than in controls, suggesting that perhaps the regeneration process, while outwardly appearing complete, is not complete within and/or between the rhinophore and brain. This may explain why nudibranchs with both rhinophores removed cannot navigate at five weeks post-removal. Future experiments are needed to determine functionality of regenerated rhinophores from a neuronal activity standpoint.