The Case of the Corpulent Caudate


While I impatiently wait for the field season to come around again, late February offers a chance to get out and get a little taste.  Several fish-less ponds in a small nature preserve not far from where I live provide an opportunity to find a few Smallmouth Salamanders (Ambystoma texanum).  For the past several decades I've been able to reliably find them at this location during the tail-end of the winter season.

The air temperature was in the mid forties on the afternoon I made a visit to the preserve.  The main pond had a thin layer of ice with a few open areas here and there, and the volume of water was much higher than the previous February.  Finding texanum this time of year is easy to do - they have moved from their winter quarters underground into the pond in order to mate and lay eggs.  I walked the perimeter of the pond, looking for logs and fallen branches that were half in the water and half on the bank.  Under these I could usually find several Smallmouths without needing a dip net, while keeping my feet dry.

The first such log I rolled yielded a skinny male texanum with a nubby little tail.  He looked like he could use a few good meals, and I was sure he would fatten right up once his reproductive responsibilities were met.  Several more logs each held male salamanders under them, and one had several masses of eggs underneath.  I always feel good when I find eggs or larvae or neonates - all seems right with the world, at least for one more season.

I turned over a half-submerged section of bark and was quite surprised at the Smallmouth I found underneath.  Far from thin and emaciated, this salamander looked like a stuffed sausage!  The body bulged in between each costal groove. and the head and neck were also bloated.  As I took some pictures, I noticed that along with the limbs and digits, even the tissues around the eyes were swollen.

After examination and pictures, I put the poor little guy (it looked like it could be a male) back under the log and wished him well.  What could cause such swelling?  Was this salamander doomed?  Later, I posted pictures of the animal on Field Herp Forum - perhaps someone had seen this condition before.  No one had, but a number of veterinarians shown the pictures (thanks, Warren!), identified this condition as edema, an abnormal accumulation of fluid in body tissues.  Given the permeable skin of salamanders, this was a serious condition to have.

We humans hardly have a lock on life-threatening diseases and conditions.  Life is hard on all organisms; edemic salamanders join the ranks of one-eyed frogs, blistered snakes, and turtles with missing limbs.  I hope the salamander got over his condition, but even more I hope that his was an isolated problem that isn't affecting the rest of the Smallmouth Salamanders in the pond.


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