It’s puzzling that some animals are capable of entirely replacing a lost limb and that others cannot. Our working group has recently put together a few ideas about what factors may restrict appendage regeneration. Specifically we focus on the possible constraints of body size, age, life stage, and growth pattern in affecting the recapitulation of development and the regrowth of that newly patterned limb. Our paper is published here online in Biology Reviews (Biol Rev Camb Philos Soc. 2011 Sep 19. doi: 10.1111/j.1469-185X.2011.00199.x. [Epub ahead of print]). Stay tuned for a data paper testing some of the proposed hypotheses using salamanders.
This paper is authored by the Nexus Biology Group at University of Florida: Ashley Seifert, James Monaghan, Matthew Smith, Bret Pasch, Adrian Stier (me), François Michonneau and Malcolm Maden. Our work was generously funded by the Singer Biology Fund at University of Florida.
One of the most compelling questions in evolutionary biology is why some animals can regenerate injured structures while others cannot. Appendage regeneration appears to be common when viewed across the metazoan phylogeny, yet this ability has been lost in many taxa to varying degrees. Within species, the capacity for regeneration also can vary ontogenetically among individuals. Here we argue that appendage regeneration along the secondary body axis may be constrained by fundamental traits such as body size, aging, life stage, and growth pattern. Studies of the molecular mechanisms affecting regeneration have been conducted primarily with small organisms at early life stages. Such investigations disregard the dramatic shifts in morphology and physiology that organisms undergo as they age, grow, and mature. To help explain interspecific and intraspecific constraints on regeneration, we link particular fundamental traits to specific molecular mechanisms that control regeneration. We present a new synthesis for how these fundamental traits may affect the molecular mechanisms of regeneration at the tissue, cellular, and genomic levels of biological organization. Future studies that explore regeneration in organisms across a broad phylogenetic scale, and within an ontogenetic framework, will help elucidate the proximate mechanisms that modulate regeneration and may reveal new biomedical applications for use in regenerative medicine.