HCA: Hermit Crab Association

Is there a way to tell how old a hermit crab is?


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I would be interested in what the super-long-term crabbers have to say about this. Mine have certainly grown fairly consistently as long as I have had them, so I think it is fair to say that their relative size is at least related to how old they are, although I'm sure it is not perfectly correlated, as conditions and diet are sure to have some effect on how fast they grow (and I've read of crabs apparently getting smaller after a difficult molt trying to repair serious injury). I don't know if there is anything else that might be a better indicator; let's see what the "gurus" have to say!

This artcle was a interesting read. https://animals.mom.me/how-to-tell-how- ... 95998.html


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That is a good one. Assuming they are correct, it give several different indicators. Taking them all together, I guess you can at least get a general guess.

Unless it was born in captivity, no. Theres not accurate way, at most its an educated guess. Size of crabs usually an indicator that they are old, but not necessarily older (crabs do grow at different rates)

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Not reliably. Bigger = older. That's about as far as we can get. Growth rates are extremely variable, severe injury can reset size, I've had crabs shrink during molting, and even Carol Ormes says her two oldest are smaller at 40 than some wild caught crabs have been so there is stunting in captivity.

There are ways to do it once they are dead. Crustaceans have internal structures (inside the eyestalks and part of their gastric mill) that are retained when shedding and can be dated like tree rings. I haven't seen a study on doing it with hermit crabs in particular, but it should hold true though may require adjustments on how long it takes for a layer to form.

wodesorel wrote: ↑

Tue Dec 24, 2019 2:48 am

There are ways to do it once they are dead. Crustaceans have internal structures (inside the eyestalks and part of their gastric mill) that are retained when shedding and can be dated like tree rings. I haven't seen a study on doing it with hermit crabs in particular, but it should hold true though may require adjustments on how long it takes for a layer to form.

That's fascinating. I'm guessing what that will tell you literally is how many MOLTS they have undergone?

DragonsFly wrote: ↑

Tue Dec 24, 2019 11:21 am

That's fascinating. I'm guessing what that will tell you literally is how many MOLTS they have undergone?

In lobsters and other crustaceans it's listed a yearly ring, not by molt. I don't know enough about them to know if their molting cycle is cyclical with the seasons so would make it perfectly line up. I would think it would be by molts as well!

I remember a nature show about lobster's yearly migrations, so at least some of them must molt according to that cycle.

My two crabs hatched on 4th December 2016 and are totally different in size. They have had the same conditions and access to the same food and shell choices their entire lives so size doesn't really give an indication of age other than bigger is usually older BUT having said that bigger is NOT older in my case.

Just wondering, did you end up tracking the growth of your crab?

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