Red Claw Crabs - Moulting/death

[sophiegackowski]

Hi everyone,

noticed this past couple of days that the crabs have been out of the water alot more than usual - they appeared to be puffing themselves up with the little puches on either side of the mouth...anyway they were fine, active etc - and I thought perhaps a moult was coming on. I was right.

Woke up this morning and counted 5 crabs (I have 4) but 1 was flat on his back and 1 was under a flower pot. So I had a little nosey just to check if they were both shells and it appears that one has moulted and one has just died. Yesterday he had his egg flap open and a long transluscent appendage was coming out of it.

Just not sure if it's dead - definitely not moving, looks lifeless, but I'm going to wait and see for a while as I've heard of complications - although he shouldn't really have been on his back should he.

Any help or advice would be brilliant.

Thanks.

Red claw crabs btw! I forget sometimes not everyone knows

Before anyone asks as well - they have access to land, brackish water, a varied diet...

 

[nmonks]

Crabs do indeed swell up with water shortly before moulting. I believe this is related to how they crack open their old skeleton and puff the new one into shape. Iodine (used in marine aquaria) seems to help those crustacean species that have problems moulting successfully. While you can't do much to help a crab after it's moulted, you can certainly add iodine from now on and hope the others do better. In theory at least, a crab can put right a faulty moult during successive ones, though that assumes it can move about and feed normally in between.

As for problems during moulting, these are most often to do with crabs interfering with one another. Partly, mating can be an issue: crabs can only mate when moulting. But it's also likely that under aquarium conditions crabs view one another as territorial threats and when moulting at least, maybe even potential food.

Cheers, Neale

 

[sophiegackowski]

Well one of them has moulted and is fine, I can see him (he's not hiding for some reason) but appears to be fine, moving etc but I can see he looks different and bigger! I did think about iodine as you mentioned it before, but I worried that if I used too much this could cause complications also. Do you know anything about their mating process? I can't find anything anywhere. I'm worried about the others, I don't think there was any interference in the sense of eating each other etc as the crab that appears to be dead is completely in tact. He just has that egg flap open.

Should I leave it or is there no hope if it's not moving and on its back?

Thanks Neale,

Sophie

 

[nmonks]

The addition of iodine does help both crabs and crayfish, and is now considered practically essential when these animals are kept. Without it, moulting problems do seem to happen eventually. Use half the dose quoted for marines.

They have been bred in captivity once or twice; see for example here. But my comment about crabs breeding during the moulting period comes from my general zoological background (my first degree was zoology). Put simply, the male has nowhere to stick his penis (for want of better terms) until the female moults. In our native shore crab, the male will then clamber on top of the female, using his body to protect her until her shell has hardened.

I wouldn't do anything to a recently moulted crab except, possibly, isolate it by placing some sort of "trap" over it to keep other crabs from getting in. You could use a clean (non-used) laundry detergent measurer or ball with a few holes drilled in it for air. I use these for all kinds of things, such as keeping eggs safe in community tanks! Very useful.

Cheers, Neale