Meeting Abstract

45.5  Saturday, Jan. 5  How similar are regeneration and fission in naidine annelids? BELY, A.E.**; ZATTARA, E.; BURTON, P.M.; SIKES, J.M.; NYBERG, K.G.; Univ. of Maryland, College Park abely@umd.edu

Many animals with high regeneration potential can also reproduce by asexual agametic reproduction (eg, fission, budding). In groups such as annelids, both phylogenetic and developmental evidence suggest that the process of reproducing by fission is evolutionarily derived from regeneration. Despite this close association between fission and regeneration, we have found that in one group of annelids, the naidine oligochaetes, the ability to regenerate can be lost even in lineages that retain fission. We have undertaken a detailed developmental comparison of fission and regeneration in the naidine Pristina leidyi to identify specific similarities and differences between the two processes, with the goal of elucidating by what steps fission evolved from regeneration, and how these two processes might become evolutionarily decoupled in some naidines. We have investigated nervous system changes, musculature changes, cell proliferation, cell migration, programmed cell death, loss of nephridia, morphallaxis of the gut, and the timing of major morphogenetic events during both fission and regeneration. Despite extensive similarities, we have identified several important differences between fission and regeneration, most notably in the development of the new nervous system.