Meeting Abstract

P3-21   -   Regeneration of rhinophores in the nudibranch Berghia stephanieae and the underlying role of cell division Ricks, L*; Wightman, E; Newcomb, JM; New England College; New England College; New England College lricks_ug@nec.edu

Regeneration has been studied in many organisms, such as cnidarians, flatworms, and even vertebrates. In some of these animals, regeneration relies on cell division, while in others, remodeling of differentiated tissues is important. Regeneration is also exhibited by a number of mollusks, but the prevalence and its underlying mechanisms are largely unknown. The purpose of this study was to determine if the nudibranch Berghia stephanieae can regenerate its rhinophores and, if so, to investigate the extent of cell division in this process. In one experiment, both rhinophores were amputated from 10 animals, and the lengths of regenerating structures were monitored every few days, for several weeks. The rhinophores did regenerate and attained their original length within 2 weeks, while also reforming typical anatomy. During the first 2 weeks, the rhinophores grew at an average rate of 106 µm/day, whereas after this, growth slowed to 38 µm/day. Thus, regeneration occurred at a faster rate than constitutive growth. In the second experiment, we used antibodies for phosphorylated histone 3 (H3P) to label dividing cells in regenerating rhinophores. Animals were fixed immediately, and also 4 hours, 1 day, 3 days, and 7 days, after removal of the rhinophores. The number of H3P-positive cells was compared between amputation sites and neighboring regions for all time points. While cell division was noted at amputation sites, the H3P-labeling in these areas was not significantly more than neighboring regions until 3 and 7 days after rhinophore removal. Thus, there was a constitutive level of cell division, and this was significantly increased during regeneration several days after amputation. Together, these experiments suggest that B. stephanieae can regenerate body structures such as the rhinophores, and that high levels of cell division may be important in this process.