HCA: Hermit Crab Association

I got a a handful of Crabs like 6 months ago and all but two of them have at least tripled in size. I accidentally disturbed them while rearranging the tank last night. These two went under about a month after we got them and I hadn't seen them until last night when I accidentally disturbed them. I gently scooped the dirt around them up along with them and set them in bowls and set up a little isolated section for them. Temps are right, humidity is right, diet is balanced, I don't even use a light. I don't handle them. I don't understand.

I'm a little confused. On the crabs that you are concerned about have they just recently molted? Or have they molted multiple times with you? After a molt a crab may actually appear smaller until growing a bit from previous "shell/exo" and will take a bit to appear larger, but crabs can't really grow much without molting. The more molts and time you have them, the larger they will grow.

Hopefully that helped some. If you add a few more details, you'll prob get more responses as to if you should be worried or not if your crabs aren't molting. Although you had written that they aren't growing not that they aren't or haven't molted. It is late and I'm exhausted from work so maybe I'm misreading your post. Will check back though.

More details would be important; you don't say how many crabs you have, what size tank or depth of substrate, how large the crabs were when you got them, or anything about their previous existence. Not knowing any of this, here are some speculations:

1) If those two were the biggest, it generally takes crabs longer to molt as they get bigger/older. It is unfortunate that you disturbed them, as they may have been mid-molt. Hopefully they will complete whatever process they were in and be okay.

2) If they were all about the same size, those two may have been injured, or more damaged in some way from their previous traumatic experiences (just being abused into captivity, or if they were in not-so-good conditions before they got to you). They may therefore have needed more time to molt and heal from that previous damage, whereas the other crabs were not as damaged and therefore could go ahead with molts that were mostly focused on growth rather than healing from damage.

3) It may be that these two were just so damaged from their previous experience that they actually can't adjust to captivity at all, and may not make it. Let's hope it isn't that.

4) It could be that you have too many crabs in too small a space, and they are intimidated to surface and interact, and/or don't feel safe to molt (too great a chance of cannibalization).

5) It's possible that they actually have been coming up at night, during times you aren't observing, and have not molted yet at all. This may be just because they haven't felt the need to, or may be because they are suppressing molting for some reason (don't feel safe? conditions not quite right for them?). If they have been suppressing molting, that could be dangerous for them. If they just haven't needed to, maybe they are just "slow" compared to the others? Or again, if they were larger than the others to begin with, they may just not have needed to yet.

6) Are they in painted shells? There have been cases where crabs in painted shells were stuck to the shells from paint inside the shell that wasn't fully dry before they were forced into the shell, and therefore unable to molt successfully. I'm sorry to say that, if that is the case, there is likely nothing to be done.

Those are just a few ideas. Likely providing safe (free from other crabs that might try to cannibalize them), dark places for them with proper conditions and some tiny food sources is all you can do--and wait. Crabs are, if nothing else, amazing teachers of the dying virtue of patience.

Best wishes; I hope they come through okay!

I would also say, if they are from pet stores, or people you have adopted them from, a lot of times the shells they're in are too small in comparison to their bodies. When they change into new, appropriate sized shells, they appear MUCH larger then they were before.

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1) they were the smallest,
2)they are all different sizes from dime sized to about half of my palm now when I got them though they were all the same. Aside from my three large ones. I got a group of six that were all about dime sized and they were all weak four of them have at least tripled in size the two have been under for at least a month if not two. One just surfaced a couple days ago he passed away this morning. His faced and limbs had doubled, but when his body fell out of the shell his abdomen was still so tiny, it was too small for hi body.
4) I may be pushing it on space but since I got the last three my other four that are healthy have started to thrive. They didn't grow until I got them they didn't play or eat much. I currently have I think 9 in a 75 gallon.
6) they haven't been in painted shells at all.
Also I did put them in isolation when I accidentally disturbed them.

Crabs grow at completely different rates! I've had some triple in size in a single molt, but others who did not noticeably grow at all. Molts that are repairing any damage or injuries take a lot of energy and reserves, so major growth is usually on hold for those.

What usually happens in my tanks is a few molts with moderate to low growth, and then one molt with major growth, and then back to low growth. It tends to alternate at the very least.

In the arthropod world, slow and steady growth tends to be the healthiest. Growing too fast in some species is known to cause severely reduced lifespans and major health issues. We never seem to talk about that subject with hermits, but it could very well be a factor in why exotics for instance don't live very long in captivity. I've been very careful in how I feed my Ruggie just in case.

wodesorel wrote: ↑

Wed Nov 20, 2019 9:33 am

In the arthropod world, slow and steady growth tends to be the healthiest. Growing too fast in some species is known to cause severely reduced lifespans and major health issues. We never seem to talk about that subject with hermits, but it could very well be a factor in why exotics for instance don't live very long in captivity. I've been very careful in how I feed my Ruggie just in case.

That's fascinating, wodes--what do you do differently with the Ruggie?

DragonsFly wrote: ↑

Sat Nov 30, 2019 9:06 pm

That's fascinating, wodes--what do you do differently with the Ruggie?

I feed every three to four days, on the same schedule as my crested gecko, since they get the same food. (My crested tends to get overweight easily, so he's on a controlled diet, too.)

wodesorel wrote: I feed every three to four days, on the same schedule as my crested gecko, since they get the same food. (My crested tends to get overweight easily, so he's on a controlled diet, too.)

On a related note, I wonder if what is fed may matter, as well.

I’m sure a crab that eats primarily protein, carbs, and fats is going to grow faster than one that prefers fruits, leaves, and vegetation.


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