This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Animals vary dramatically in their ability to regenerate lost body parts. Many cnidarians (e.g., anemones), annelids (segmented worms), and platyhelminths (flatworms), for example, have fantastic regeneration abilities and are capable of regenerating an entire adult from a small portion of the original animal. In contrast, most amniote vertebrates (mammals, birds, reptiles) and ecdysozoan phyla (e.g., arthropods, nematodes) are relatively poor regenerators; though capable of some limited regeneration, almost none of these organisms can regenerate parts of their primary body axis and none can regenerate a complete body from a small fragment. The phylogenetic distribution of regeneration potential across animals strongly suggests that the ancestral animal had extensive regeneration abilities and that loss of regeneration abilities has been a major evolutionary trend in many animal lineages. Understanding the ultimate and proximate causes of regeneration loss requires a detailed understanding of the evolutionary forces and developmental mechanisms operating in regenerating and non-regenerating species, preferably closely related ones. We have identified a group of small, freshwater annelid (segmented) worms, the naidine oligochaetes, that includes closely related species differing markedly in their ability to regenerate their heads. Head regeneration appears to be ancestral for the group and non-anteriorly regenerating species are likely to represent at least two independent and relatively recent evolutionary losses of regeneration ability. Naidines are therefore an excellent system in which to investigate the underlying causes of natural losses of regeneration ability. We are currently investigating a range of developmental phenomena (cell division, programmed cell death, cell migration, nervous system dynamics, body patterning) across both regenerating and non-regenerating species (NSF grant IOB-0520389) in order to identify processes which occur normally and which fail to occur in non-regenerating species. We are now eager to expand our studies to include bioelectric events, such as ion currents and voltage gradients, which are increasingly being recognized as intimately linked to the potential to regenerate. Our main goal for the current project is to describe membrane voltage changes and ion currents during the first 24 hours following head amputation in at least one regenerating species (our primary focus would be on Pristina leidyi, which is particularly transparent and easy to manipulate) and then to investigate these features in at least one of the non-regenerating species. Our expectation is that regenerating and non-regenerating species will display markedly different patterns of post-amputation voltage changes and ion fluxes.
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