Regeneration
From the Science in the clouds blog.
Barbicambarus cornutus with its molt from UK biological station (EREC).
What is regeneration?
Here we'll focus on the best known vertebrate regeneration example: the salamander. The picture on the right depict limb regeneration process in salamander. It starts with an amputation of course, in nature it could be a failed predation attempt for instance. Then, wound is healing (1) by migration of cells over the wound to cover it. At this point more cells are migrating to the wound spot creating what we call a blastema (2). It is an accumulation of cell among which lots of them start the process of dedifferenciation, they reverse from their attributed role (whatever it was they were doing from bone to nerve to blood vessel) to a state where every fate is possible (think about stem cell). This is the crazy step that we human can't do (although humans can completely regenerate the tip of their finger until the age of 11). At that point, proliferation can take place (3). All those dedifferentiated cells start multiplying and building a new limb. The process continues until a complete limb as been formed (4 & 5) and it is fully functional!
In crayfish, the organism that I'm working on, regeneration cannot take place continuously ... they are invertebrates. Meaning they are wearing their bones like we do with our skin, it's all inside out! Indeed, crayfish and other invertebrates do not grow continuously, they molt: they extract themselves from their own skeleton and then grow before building a new skeleton around them (on the left you can see a picture of a crayfish with its fresh molt). It's crazy, no?!
Why regenerate? And why crayfish?
First, regenerating is bad-ass, humans have been after that power for a long time ... that's why we have so many scientists working on it nowadays. The idea is for one day to be able to inject someone with a serum at the wound location and induce the regeneration process. The applications are obvious from limb loss due to war or accidents or malformation at birth to crazy ideas like removing cancer with the organ where it occurs and regenerating a new organ ... this last one is still science fiction, but dreams are cheap and they work your imagination!
Focusing on crayfish, if you have been on the ecosystem engineering page you now know their engineering capacities, if not go check it out and come back we'll wait for you. The idea here is to use crayfish regeneration to modulate their engineering capacities. Indeed, crayfish mainly use their first pair of chelae (the big pincers) to dig up their burrows (see image on the right) creating new space and inducing turbidity by sediment suspension (their main engineering features). As scientists I am always looking for ingenious ways to modulate a natural phenomenon in order to investigate it, regeneration provides me with the perfect way to inhibit crayfish engineering and then to document its changes over time during regeneration. That's exactly what I'm doing for my Ph.D. dissertation!
Another crayfish (Barbicambarus cornutus) with its molt from my previous lab at UK. The orange mesh is to provide them with some structure.
Morphology of crayfish burrows: A, that of a primary burrowing species; B, C, D,
those of a secondary burrowing species; E, that of a tertiary burrowing species (from Hobbs 1981)
Scientific papers you might want to check out ...
I haven't published any of my work involving regeneration yet, but I'm working on it! In the meantime, I can direct you toward some resources that you can easily find online or even buy for a small fee:
- Vertebrate Limb Regeneration, by Hugh Wallace (ISBN: 0471278777) - Amazon link. This book is maybe a little bit old (1981), but it's witty and still the best introduction to regeneration!
- Principles of Regeneration Biology, by Bruce Carlson (ISBN: 0123694396) - Amazon link. The regeneration compendium in my opinion.