How important are day/night cycles to crabs?

[emmac350]

I know that some of the older info out there about crabbing says that if a crab is stressed, it should be put in complete or near-darkness until it isn't stressed. But I'm noticing, now that I have a day cycle that's more obvious for the crabs (a full spectrum fluorescent on a timer so it's consistent) they're out more, even though my schedule is currently crazy (up at 0330 one week, up at 0615 the next week...rinse, repeat) and I have to turn on lights in rooms that light up the crabs at, say, 0330 but then it's dark for them again by 0430. So despite the schedule craziness, my crabs are definitely benefiting from the day cycle even though I don't have a moon glow bulb yet.

But what if a crab is stressed or molting? Old wisdom said that you should put the crab into a dark place - say, a closet - until it had recovered or died. This just doesn't make sense to me. With as much as my healthy crabs enjoy having a slightly normalized schedule (daylight definitely happens for 12 hours), I would assume (maybe incorrectly) that taking a crab from even just a normal life schedule (knowing when it's light or dark) would stress it out worse. If I was sick (unless my eyes had gone bad somehow) I would freak out if it was suddenly dark all the time. So why should anyone put their crabs through the added stress of isolating and moving into a completely dark place? It disrupts circadian rhythms for one thing, which could just stress them out more.

I'd like some input on this please - my brain says that utter darkness is bad - they don't get complete darkness pre-molt in the wild, so why is it so important we give it to them when they molt or are stressed? I understand moving them to a less-used area of the house so they don't see huge things outside their tank all the time, but not complete darkness.

[ladybug15057]

Hermies must have the darkness for their molting hormones to kick in properly. But they must have a day/night cycle to their lives. (Confusing isn't it?) Some hermies do burrow for molting, possibly why it takes them so long under the substrate, in the darkness? For their molting hormones to kick in totally, because the shedding of the exo, eating the exo, and recovering doesn't take all that long. Being one with many surface molters, as some other crabbers have had surface molters can also confirm molting and recovery doesn't take all that long. In fact not even 1/2 as long as it takes most molters who burrow.
A hermie will seek the lighting/darkness they need when they need it but being crabbers we must provide it for them for them to choose what they need. Some hermies will remain in huts most of the day, some burrowed, some will scoot about the tank. A little saying that was said:

"Remember the light stimulates the metabolism and the metabolism is fueled by food and the metabolism is how the crabs adapt to their environment by adjusting their body temperature."

[emmac350]

I understand the whole molting hormone/darkness thing...but I'm more talking about if you have a sick crab, or a new one. If a crab, say, were to get overheated but hasn't died yet, would it be better to leave it in its current conditions of light and dark (maybe placing a cocohut or something over it to give it SOME darkness but not total) or to place it in a completely dark place? Or if you get a new crab - should you take it from pet store conditions and then place it in a new tank in total darkness or let it keep having a normal day/night cycle so that isn't an additional stressor added to the mix (with hiding places, of course)?

[ladybug15057]

In the cases you are mentioning, the hermie needs to have the 'typical' night/day cycle to remain healthy and to adjust.