How long before drowning?

suebee · Post by **suebee** » Mon Feb 14, 2011 9:58 pm

"Hermit crabs can go underwater for a post-molt soak for 5-1hr cycles underwater? "- Energizer13 where did you get that information from?

Aetyrno · Post by **Aetyrno** » Mon Feb 14, 2011 10:03 pm

I imagine they could survive for quite a while actually... Consider that a fish, which has gills meant for breathing only water, can breathe air on land provided their gills stay moist. Since the crabs have gills which were originally intended for breathing water and adapted to breathing moist air, they should be able to extract oxygen from water just like a marine hermit crab can, though not as efficiently.

Maybe it's like a gill rinse? Wouldn't want bad breath!

CallaLily · Post by **CallaLily** » Tue Feb 15, 2011 8:42 am

Energizer13 wrote:they can not hold their breath for 1 hr as many people say!If your dish is so deep that your hermit crab falls in and cannot take a breath or get out than you may have a drowning hermit crab on your hands. Hermit crabs NEED to take breaths underwater and CANNOT HOLD THEIR BREATH!! Hope you have fun with your hermies!!!!!!

I don't think any of us on here knows for sure how long a hermit crab can or cannot hold their breath. A few of us just said that we noticed a hermit crab stay completely submerged for __ amount of time. I think it's safe to say that we all agree that it's very important to have a few easy ways out of the water dishes/pools for the crabs. No one is talking about placing a crab in deep water with no way out. Most of us on here leave bathing up to the crab.

Post by **JediMasterThrash** » Thu Feb 17, 2011 8:54 pm

This thread was about how long crabs can survive underwater. It was not about whether we should offer deep pools or not.

Anecdotal evidence has shown crabs can survive up to between 90 minutes and 3 hours under water. Their modified gills can obtain some oxygen from water, but not very well, and they will eventually drown. Nobody should experiment on this. The anecdotes come from crabbers who bathed their crabs and got side tracked and forgot about it. Not from in-tank submergers.

Modified gills can only extract oxygen from water, but require a higher concentration of oxygen. With "moist" gills, the air easily dissolves lots of oxygen in the high-surface area of moisture for the gills to readily process. With water, the oxygen content is limited.

Full gills are far more efficient than lungs and modified gills and can process a higher percentage of available oxygen, so they can work in low-concentration water.

Lungs require high concentrations of oxygen, but we use little of it efficiently.

Modified gills are somewhere in-between.

kgbenson · Post by **kgbenson** » Fri Feb 18, 2011 11:17 pm

JediMasterThrash wrote: Anecdotal evidence has shown crabs can survive up to between 90 minutes and 3 hours under water.

I know you are not saying this but I just want to re-iterate that this does not mean that this is something to try or allow, A) anecdotes are often reported in error and B) may simply reflect the exception and not the rule.

Full gills are far more efficient than lungs and modified gills and can process a higher percentage of available oxygen, so they can work in low-concentration water.

I am curious on what you base that conclusion. Specifically whose gills vs whose lungs.

Lungs require high concentrations of oxygen, but we use little of it efficiently.

Hmmmmm what do you mean exactly? This can be taken several ways. Just curious.

Post by **JediMasterThrash** » Sat Feb 19, 2011 12:25 pm

Fish vs. human.

Fish gills work with O2 concentrations 1/20th of what human lungs work with. They also use reverse bloodflow to increase absorption. Lungs have to pressure air into alveoli to increase the O2 concentration enough to permeate the membranes in sufficient quantity. And human lungs use up to 90sqm of surface area.

But lung mechanism works in air because we pressurize them, while gills collapse without fluid flow. Some articles suggest lungs evolved from air bladders, rather than gills. Any moist permeable surface area can perform O2/CO2 transfer. Amphibian skin performs a measurable amount of their "breathing".

I agree, efficient is a relative term. For the most part, I'm just referring to the concentration of O2 required for the lungs/gills to get sufficient oxygen into the bloodstream.

And I may be completely wrong.

samurai_crab · Post by **samurai_crab** » Sat Feb 19, 2011 12:43 pm

Any moist permeable surface area can perform O2/CO2 transfer. Amphibian skin performs a measurable amount of their "breathing".

With some amphibians the only way they can breath is through their skin.

kgbenson · Post by **kgbenson** » Tue Feb 22, 2011 10:20 am

JediMasterThrash wrote: Fish gills work with O2 concentrations 1/20th of what human lungs work with.

Indeed, and they require so much less O2 as their metabolic functions are significantly less than ours. We use soo much energy just keeping tropical temperatures with us internally it is amazing. So the question is - are they more efficient, or are they simply keeping up with the needs of the critters? In which case it is a wash.

They also use reverse bloodflow to increase absorption.

I believe the term you are looking for is counter current exchange system. Lovely way to extract things from a gradient.

Can anyone name a group of air breathing critters that use a counter current exchange system for respiration? This is for the bonus points.

Lungs have to pressure air into alveoli to increase the O2 concentration enough to permeate the membranes in sufficient quantity.

Gas exchange at that level is diffusion, don't go pressurizing your alveoli, you won't like it.

And human lungs use up to 90sqm of surface area.

Crammed into a relatively small volume - pretty efficient.

But lung mechanism works in air because we pressurize them, while gills collapse without fluid flow.

Kinda sorta. Both systems depend on flow (unless you play some cute tricks with rapidly oscillating air columns and that is well, lets say it never caught on. Neither system works well when the carrier fluid remains static. Water flows over gills because of pressure differences also, either generated by swimming, or gilling etc.

Some articles suggest lungs evolved from air bladders, rather than gills.

That has been the prevalent theory for quite some time now. I don't think anyone has suggested that gills became lungs for a very long time.

Any moist permeable surface area can perform O2/CO2 transfer.

Nope - many can, not all. Any surface permeable to CO2 and O2. Some are not, and yet, may be permeable and wet. The devil is in the details.

I agree, efficient is a relative term. For the most part, I'm just referring to the concentration of O2 required for the lungs/gills to get sufficient oxygen into the bloodstream.

Adequate for a fish and adequate for a mammal are vastly different things. This to must count in the equation.

Fact is, both systems serve their respective species well, the relative efficiencies are largely irrelevant.

Remember, it is not survival of the fittest, it is survival of the fit enough.

And I may be completely wrong.

No, not completely wrong. Gas exchange is a complex topic especially when you change mediums, species, needs etc. Generalizations and oversimplifications can cause erroneous conclusions though and on an animal care forum, this can be cause for some heartache.

Keith

Keith

suebee · Post by **suebee** » Tue Feb 22, 2011 3:21 pm

Can anyone name a group of air breathing critters that use a counter current exchange system for respiration? This is for the bonus points.
Me! Im one of them..Human Do i get points?

What i think Keith is saying here is, and Keith correct me if im wrong..
Lets not compare apples to oranges...? yes?? Maybe? did i lose my points? lol

Post by **JediMasterThrash** » Tue Feb 22, 2011 10:42 pm

That explains why I have such trouble convincing people that Metallica is the best R&B band of all time.

kgbenson · Post by **kgbenson** » Wed Feb 23, 2011 11:38 am

suebee wrote: Me! Im one of them..Human Do i get points?

Negative. Here is a hint - no mammals.

What i think Keith is saying here is, and Keith correct me if im wrong..
Lets not compare apples to oranges...? yes?? Maybe? did i lose my points? lol

'Zactly.

Keith

suebee · Post by **suebee** » Wed Feb 23, 2011 1:09 pm

whoops i was thinking of blood counter current exchange like in the repertory system kidneys - Do you mean more like the avian lung?

samurai_crab · Post by **samurai_crab** » Wed Feb 23, 2011 3:18 pm

Yep its birds. I wish we had their respiratory system, would make running a heck of a lot easier.

kgbenson · Post by **kgbenson** » Wed Feb 23, 2011 4:59 pm

suebee wrote:whoops i was thinking of blood counter current exchange like in the repertory system kidneys - Do you mean more like the avian lung?

Yep - crazy birds.

Keith

suebee · Post by **suebee** » Wed Feb 23, 2011 5:02 pm

I have two.. I should of thought of them first.. smack to farhead..

HCA: Hermit Crab Association

How long before drowning?

Re: Easyher