HCA: Hermit Crab Association

Hey everyone,

Im wondering if anyone knows how long a hermit crab can hold its breath under water? My water dish is deep but filled with stones and sponges. Before it was completely set up one of my E's walked into it and was walking underneath the water. He climbed out the other side but it made me curious about their aquatic-ness if you will.

I have seen PPs staying under water for about 20 minutes (they came from an awful pet shop and it was probably their first chance to bathe in months). Straws can apparently stay underwater even longer, I've heard about 30 minutes and that doesn't seem to be unusual.

Dion, and other members here have reported their straws staying under for over an hour --- aparently their gills are semi-functional under water, just as a marine hermie's gills and semi-effective on land for short amounts of time.

Straws usually stay in longest. A straw that I used to had always liked going into the salt water pool. Maybe an hour? Unsure. That was a lon time ago. Actually, not that long ago.


The Es really like to go into the salt water, also.


I wouldn't experiment with it, though, because you can drown them if you do. If they want to take a bath, then you can see how long they stay. Make sure it is when THEY go into it, and don't force them to stay inside of the pool.

THey dont essentially "breath", not like us anyways...they are more similar to fish in that they breath the oxygen transported with Hydrogen in the form of water...hence their need for humidity.

Ive had straws stay under water for around an hour, get out for 5 minutes and go right back in for another 45 minutes. Infact my baby straws I have now prefer to just sit and soak on top the filter in the ponds...they climb across the divider and then down the powercord and sit on top the filters lol! Mojito can be there for hours!

NaRnAR wrote:THey dont essentially "breath", not like us anyways...they are more similar to fish in that they breath the oxygen transported with Hydrogen in the form of water...hence their need for humidity.

I'm sorry, I have to disagree. I assume they breath like fish, which is to extract dissolved elemental oxygen from the water. Otherwise, fish wouldn't suffocate in deoxygenated water.

We'll first talk about a fish or non-terrestrial (marine) crab in the water.

Deoxygenated "blood" ("hemolymph" in a crab) flows through their gills. The blood (in case of fish) or hemolymph goes into the gill with a very low dissolved oxygen content, lower than the water.

The water has a relatively higher dissolved oxygen compared to the hemolymph. So what happens is you get diffusion through the gill membrane of oxygen from the water with higher dissolved oxygen to the blood with lower oxygen (osmosis).

That's what happens in water.

Now what happens on land?

Pretty much the same thing. Oxygen diffusion can't occur across a dry membrane. What happens is the gill is coated with a layer of water. Oxygen dissolves into the water on the surface, and osmosis occurs between the water on the surface of the gill and the hemolymph. Which is why humidity needs to be pretty high, so the water on the surface of the gills don't dry out.


Incidentally, the same kind of thing happens in our own lungs. The reason our lungs are on the inside and we secrete mucus is to keep the humidity up so we can continue to breath.

NaRnAR wrote: Not be snippy, but thats what I said. They "breath" the oxygen out of the water molecule (which is two hydrogen atoms and an oxygen atom.) And I feel that you seriously disrespected what i said by saying "I seriously doubt that" and then going on to say what I just said in a different manner. There are more tactful ways to say that in your opinion or that there is scientific proof that I am wrong.

I apoligize that I offended you. I'll go ahead and edit the post to change my wording.

But I still disagree. What occurs is elemental oxygen, O2 molecules are dissolved in water, and extracted. The oxygen in water molecules isn't considered elemental, it's in a compound (H2O). So, say out of 1 million H2O molecules, there are maybe 5 O2 molecules mixed in. Those 5 O2 molecules are the useful ones as far as respiration goes.

Water molecules are not broken down in a chemical reaction to extract the oxygen, which is what would be required to pull oxygen out of water molecules.

Schematic of the difference in the two types of molecules I'm talking about:

Elemental oxygen (two oxygen atoms with a double bond joining them)
O=O

Water molecule (1 oxygen attached to 2 hydrogens via one bond)
O-H
|
H


Again I apologize for my wording. I meant to say that I have my doubts about that hypothesis.

I had to help teach a couple of semesters of an undergraduate science class. In doing so, I found it helpful to break things down alot, as some students picked it up slower or faster than others. When not in the classroom, it can come off as condescending (and maybe even in the classroom). Oops.