# Crabs **URL:** \ **Category:** Factual Questions\ **Created:** [July 10, 2003, 12:40am UTC](https://boards.straightdope.com/t/crabs/187360 "2003-07-10T00:40:06Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Meatros](https://avatars.discourse-cdn.com/v4/letter/m/b4bc9f/32.png) [@Meatros](https://boards.straightdope.com/u/Meatros)\ **Post date:** [July 10, 2003, 12:40am UTC](https://boards.straightdope.com/t/crabs/187360/1 "2003-07-10T00:40:06Z")
Okay, my crotch has been itching lately… … Just kidding, actually I have a question about the larger and edible sea dwelling type. I went down to this place in DC (I can’t recall the name, it had _lots_ of fresh fish and was akin to an outdoor market) and something strange occured to me: They had live crabs for sale. Out of the water. Still living. Am I missing something here? Don’t crabs have gills? How could they survive on land for that amount of time?😕 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [July 10, 2003, 12:44am UTC](https://boards.straightdope.com/t/crabs/187360/2 "2003-07-10T00:44:53Z")
Crabs can spend a considerable amount of time out of water, as long as they can keep their gills moist: > [@](#): > > Crustaceans (true and false crabs, lobsters and prawns etc) need oxygen, just like we do, but instead of using lungs inside the body they use gills outside the body to get it. Gills (and lungs) work because oxygen is a very small molecule. During respiration oxygen molecules first dissolve into a layer of moisture surrounding a thin membrane. Then the oxygen molecules, because they are so small, cross right through the membrane into the circulatory system (the blood) of the animal. The source of the oxygen can either be as gas in the air or already dissolved in another liquid - like the sea. It doesn’t matter where the oxygen originally comes from, the most important factor in respiration is that the surface the oxygen molecules cross is wet. In decapods (10-legged crustaceans like crabs and lobsters) the gills are protected because they are enclosed in a chamber under the sides of the carapace (the hard shell that covers the head and thorax). Crustaceans that live in water have no trouble keeping their gills moist. Crustaceans that live on land or on rocky shores where the tide comes and goes keep their gills wet by using fluids from inside the body and by having the chamber well sealed so that very little moisture is lost. The gills themselves are feathery structures at the tops of the walking legs of decapod crustaceans. They are derived from part of the jointed walking leg. From [here.](http://www.museum.vic.gov.au/crust/question.html) ---
**Author:** ![Meatros](https://avatars.discourse-cdn.com/v4/letter/m/b4bc9f/32.png) [@Meatros](https://boards.straightdope.com/u/Meatros)\ **Post date:** [July 10, 2003, 12:50am UTC](https://boards.straightdope.com/t/crabs/187360/3 "2003-07-10T00:50:13Z")
Thanks for the quick and good information Q.E.D.! That one’s been bugging me for a bit! 😃 ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [July 10, 2003, 12:57am UTC](https://boards.straightdope.com/t/crabs/187360/4 "2003-07-10T00:57:03Z")
Yes the crabs you see in the market have gills. However all crabs can survive being out of water for some time. There are three things that kill marine life when they are taken from the water: dehydration, collapse and suffocation. Crabs have an airtight shell surrounding their bodies, so dehydration is not an immediate problem as it is for fish or soft bodied marine life. The shell also forms a very solid skeleton that prevents the body from collapsing and the internal organs from being crushed and killing the critter. Invertebrates like crabs don’t need to use a lot of oxygen to begin with, which is why it takes forever to drown insects. They have a huge anaerobic scope compared to vertebrates. Added to this many invertebrates can go into a state of torpor when faced with oxygen starvation. In this state they use virtually no oxygen, and the state is only broken by the presence of oxygen. This ability has been further refined in many crabs by the habit of spending large parts of each day/night in anoxic burrows. Even crabs that no longer do this have recent ancestors that did. They are very good at surviving with no oxygen. Many crabs of course are creatures of tidal flats, estuaries and the intertidal zone. These animals store water in the gill pouches and use that to extract the moisture that diffuses out of the air. These species would have no trouble surviving many days or possibly weeks out of water. ---
**Author:** ![Zenster](https://avatars.discourse-cdn.com/v4/letter/z/cdc98d/32.png) [@Zenster](https://boards.straightdope.com/u/Zenster)\ **Post date:** [July 10, 2003, 5:28am UTC](https://boards.straightdope.com/t/crabs/187360/5 "2003-07-10T05:28:52Z")
What’s worse than shrimps on a piano? Crabs on an organ! Carry on … ---
**Author:** ![zoogirl](https://avatars.discourse-cdn.com/v4/letter/z/b9bd4f/32.png) [@zoogirl](https://boards.straightdope.com/u/zoogirl)\ **Post date:** [July 10, 2003, 5:38am UTC](https://boards.straightdope.com/t/crabs/187360/6 "2003-07-10T05:38:57Z")
I just wanted to point out that my tanks for shore crabs have always included either a “shore” at one end or rocks and shells which protrude out of the water. The crabs often come up and spend time on the dry areas. They seem to bask in the sun, much like a reptile. Another side note; they do very well on a diet of dried shrimp. I’ve also had them eat dried, fresh or frozen “blood” or tubafex worms, commonly sold in petstores as fish or newt food. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [July 10, 2003, 6:02am UTC](https://boards.straightdope.com/t/crabs/187360/7 "2003-07-10T06:02:51Z")
Shore crabs really do need to dry out occasionally. They tend t develop nasty infections an algal growths if they are kept perpetually wet. Most crabs aren’t fussy eaters. Anything that moves to slow will make a good meal. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 10, 2003, 7:38am UTC](https://boards.straightdope.com/t/crabs/187360/8 "2003-07-10T07:38:30Z")
Not to mention that there are species of crab that spend almost their entire lives out of the water (google on Christmas Island). ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [July 10, 2003, 9:54am UTC](https://boards.straightdope.com/t/crabs/187360/9 "2003-07-10T09:54:00Z")
Shit. It’s all **Zenster’s** fault. What’s better than roses on your piano? Tulips… ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [July 10, 2003, 11:38am UTC](https://boards.straightdope.com/t/crabs/187360/10 "2003-07-10T11:38:43Z")
Meatros writes: \> I went down to this place in DC (I can’t recall the name, it had \> _lots_ of fresh fish and was akin to an outdoor market) . . . You were at the Wharf Street Seafood Market in SW Washington D.C., I would guess. ---
**Author:** ![Sock\_Munkey](https://avatars.discourse-cdn.com/v4/letter/s/aeb1de/32.png) [@Sock\_Munkey](https://boards.straightdope.com/u/Sock_Munkey)\ **Post date:** [July 10, 2003, 11:45am UTC](https://boards.straightdope.com/t/crabs/187360/11 "2003-07-10T11:45:34Z")
> [@](#): > > \*Originally posted by Mangetout \* > \*\*Not to mention that there are species of crab that spend almost their entire lives out of the water (google on Christmas Island). \*\* I saw a show on the Discovery channel about them, all I can say is that is one honkin buttload of crabs! ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [July 10, 2003, 12:47pm UTC](https://boards.straightdope.com/t/crabs/187360/12 "2003-07-10T12:47:17Z")
> [@](#): > > \*Originally posted by Eleusis \* > \*\*Shit. It’s all **Zenster’s** fault. > What’s better than roses on your piano? > > Tulips… \*\* Q: What’s better than roses on your organ? A: Tulips. Think about it. ---
**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\ **Post date:** [July 13, 2003, 3:57pm UTC](https://boards.straightdope.com/t/crabs/187360/13 "2003-07-13T15:57:40Z")
Well duh, the complete punch like was “tulips on your organ”. I thought that was implied after Zensters joke.