Demystifying Regeneration: Lessons Learned from an Annelid Worm

Regeneration, the ability to re-grow a missing body part after it has been removed, is seen in many phyla across the animal kingdom.  However, the degree to which regeneration occurs varies.  For example, some amphibians can regenerate limbs while some fish can regenerate fins.  In addition, the mechanisms for regeneration differs.  In some planarians, stem cells are readily available to differentiate into needed cell types while Hydra can regenerate without cell division.  An essential question of regeneration studies is what is the origin of the regenerative tissue?  Though many annelids can regenerate following transverse body amputation, the cellular mechanisms of regeneration in this phylum are poorly studied.  The purpose of my project is to describe what happens in regenerating juveniles of the annelid Capitella teleta.  Juveniles are more transparent and regenerate faster than adults.  This study aims to characterize the cellular events during posterior regeneration.  To visualize cell division, a modified nucleotide is incorporated into DNA in cells undergoing mitosis.  By two days post-amputation, positive labeling in the posterior of the animal marks the onset of cell division.  Cell division in the regenerating juvenile is detected in all three germ layers.  New segments reform and normal development is re-established by nine days post-amputation.  DiI, a vital marker, aids in visualizing cell behavior.  Antibody labeling can visualize regenerating patterns of different cell types.  A detailed understanding of cellular patterns seen in regenerating juveniles sets the foundation for future studies on determining the origin of the regenerative tissue in this system.