A question has been directed to me about the physiological relationship between a nematode and its vertebrate host - and I really don’t know anyone with the right expertise.
Maybe one of you can tell me where to redirect the question?
Q: I work with porcupines in the Catskills. As herbivores, they get insufficient sodium in their tree leaf and bark diets, and must seek supplemental sodium to satisfy demands of muscle and nervous tissue. Like all herbivores, porcupines have an internal sodium pool on which they can draw at times when supplemental sodium is unavailable. In ungulates, the sodium pool is in the rumen. In porcupines, rabbits, beavers, and perhaps other post-gastric fermenters, the sodium pool is in the caecum.
The caecum of the porcupine is about 200 cc in volume, and houses around 30,000 large nematodes of a single species, Wellcomia compar. This nematodes are large, about 2 cm long, so they fill the caecum like noodles fill noodle soup. Each porcupine species tested (there are 27 though not all have been tested) has its own species of Wellcomia, and this applies to both Old-World and New-World forms, which separated some 30 million years ago but share a common ancestry.
The strong evolutionary association between porcupines and their nematode symbionts suggests a mutualistic relationship. It is my personal belief that the nematodes play some role in maintaining the sodium pool. For one thing, they would have to live in a high-sodium environment to use their own muscles and nerves. To the best of my knowledge, no one has ever studied the question in porcupines. Do you know of any other nematodes that may influence their external sodium supply?
Thanks, David Hall