synchronised moulting?

[Mike Colley]

I've been keeping Tarantulas for a year now and have 10 so far. Although I have not kept accurate records I have noticed month by month that moulting seems to happen in regular patterns, particually in the youngsters. I wondered if anyone one else had observed this or if it was pure coincidence.

It would also seem that moulting is regular until the spiders get to around 2 inches in length then it dramactically slows down.

Cheers
Mike

[Stanley A. Schultz]

I've been keeping Tarantulas for a year now and have 10 so far. Although I have not kept accurate records I have noticed month by month that moulting seems to happen in regular patterns, particually in the youngsters. I wondered if anyone one else had observed this or if it was pure coincidence. ...

First, read http://ezinearticles.com/?Same-Day-B...dox?&id=414974. (The first 1/3 to 1/2 is drivel, but the last part is important.)

Then, read http://en.wikipedia.org/wiki/Birthday_problem. (This explanation may likely be beyond your level of mathematical expertise.)

Or, Google the following search strings while retaining the hyphens:

birthday-paradox

birthday-problem

This apparent synchronicity of molting times may merely be, in part, the result of this phenomenon.

Add to that the fact that as tarantulas grow they tend to become locked into an annual cycle, usually with them molting in the spring of whatever hemisphere they happen to be living in. (The Chilean rose, Grammostola rosea, provides an interesting example of this. See http://people.ucalgary.ca/~schultz/roses.html.) Thus, by the time a tarantula reaches a size comparable to an adult, it will have become entrained to the seasonal cycle in its geographic area, thus concentrating almost all the molts in a collection into just a few weeks. Obviously, there will be a bunch of coincidental molts in such a situation.

It would be easy to spin the story that baby tarantulas also tend to synchronize their molts, perhaps as a survival strategy to avoid cannibalism. But, then one must demonstrate some mechanism that coordinates their molting cycles over relatively long periods of time. This might imply a biological clock of uncanny accuracy. But, there doesn't seem to be much other evidence of such a mechanism.

Or, one must demonstrate some feedback or interplay mechanism between them that allows them to synchronize their molting. This is difficult to do because the baby tarantulas in captivity are kept separate, usually one each per container and at some distance from each other, with almost no interrelations.

Is what you think you see merely a figment of your imagination? Probably not, because others have also reported similar coincidences. In fact, the spring molting season has sometimes been called the "molt-orama!" (See http://dictionary.reference.com/browse/-rama for a definition and origin.)

But, as with most aspects of tarantula biology, it has not been verified and confirmed either statistically, by experiment, or even by a believable, working explanation.

PhD thesis anyone?