Crayfish are fully aquatic freshwater crustaceans that can tolerate wide ranges of water temperatures. At the same time, in their natural habitats, they can even survive the drying up and loss of their streams and ponds. Thus, people wonder, do crayfish need to come out of water?
Although they can venture onto land, they do that only in certain circumstances. Other than that, crayfish do not need to come of water.
Do crayfish need land? Do crayfish Need Air? How do crayfish breathe on land? Can crayfish live completely submerged?
In this article, you will find out answers to these and some other questions about crayfish.
The Respiratory System of Crayfish
For better understanding, we need to know how their respiratory system works.
Crayfish do not have lungs as mammals do, nor do they breathe through their mouths. Instead, they use gills to breathe in water.
The gills are branching organs located in branchial chambers on the side of the crayfish cephalothorax.
In crayfish, the exchange of respiratory gases and ions occurs when water is drawn into the branchial chambers and circulated over the gill surfaces.
Each gill chamber is ventilated by a paired respiratory pump in the form of beating scaphognathites.
Interesting fact: Actually, gills are located outside of the body cavity in a space between the body wall and the carapace. Therefore, technically, gills are external extensions of the body surface. Whereas lungs are internal folds.
Do Crayfish Need Air?
Such words as ‘Oxygen’ and ‘Air’ are often used interchangeably but they are not the same. Oxygen is an important gas in the air we breathe.
There is only 21% of oxygen in the air. In the water, its concentration is only 1/20 the amount of oxygen compared to the same volume of air.
Therefore, the question itself is not well formulated.
Crayfish need oxygen, not air. Their breath is carried out by complicated gills that are significantly bigger than the size at first glance.
The structure, size, and location of the gills allow crayfish to efficiently remove oxygen from the water and from the air, as long as the crayfish’s gills stay moist.
I need to repeat that “as long as the crayfish’s gills stay moist” is the most important part here! Otherwise, they cannot stay out of water for a long time.
Important: According to the study, in crayfish, an increase in temperature causes a reduction in the oxygen-carrying capacity of hemolymph and oxygen binding to hemocyanin (crayfish blood), which ultimately affects the delivery of oxygen to tissues and leads to an increased mortality rate.
How do crayfish breathe on land?
Crayfish gills pull oxygen into the bloodstream as water (including humid air) passes through them.
That is why some scientists say that crayfishes are facultative air-breathers that use air-breathing to supplement aquatic respiration in hypoxic (low oxygen) waters.
Retaining gill moisture, as a diffusion medium, while accessing a reliable source of atmospheric oxygen is critical for a crayfish in a low oxygen aquatic environment.
Why do crayfish come out of water?
OK, if crayfish are fully aquatic animals why do they keep crawling on land? Actually, this is a reasonable question.
Generally, there are 2 main reasons why they do it.
- Crayfish are generally tolerant of low oxygen. However, prolonged exposure to very low oxygen can be harmful even to them.
So as to avoid injury and maximize chances of survival (self-preservative instinct), crayfish will try to leave the water or reach the water surface to expose their gills to higher oxygen levels at the surface.
Note: In the aquarium, the water should be aerated to improve water quality for the crayfish
- High competition and limited food supply can be another reason why crayfish may come out of the water. They are trying to find new habitats to survive. As we can see, it is all about self-preservative instinct.
Some aquarists may say their crayfish have enough food and they do not have any aggressive tankmates but they still try to climb out of the tank. Why?
Because even our biggest aquarium setups are not big enough for most crayfish species that we keep as pets. In the wild, they can cross large distances. Whereas in our aquariums they are very limited. In their world, they are simply trying to find a bigger puddle.
How long can crayfish stay out of the water?
Crayfish can maintain a store of water in the branchial chamber that covers the gills. Basically, it allows for simultaneous gas exchange with two media (air and water).
Thus, as long as their gills are moist enough crayfish will survive out of water.
We should not forget that depending on the species, humidity, and size of the crayfish their ability to stay out of water may range from a few hours to several days or in some species even months.
Thus, it would be wrong to generalize and say that crayfish can live 5-7 days out of the water, as some articles do. For example, dwarf crayfish species often die within 48 hours whereas Yabby (Cherax destructors) is able to survive several months in the burrows.
Can crayfish live completely submerged?
Yes, they can. As long as there is enough oxygen in the water, they can live permanently underwater.
Of course, given the opportunity, they can get out of the water for a while each day. As I have said before, they can do it during exploring the environment.
Note: All crayfish species are great escape artists. So, a tight-fitting lid is essential for the tank.
Do crayfish need land?
Generally speaking, most crayfish species do not need it unless oxygen concentration is very low in the water.
Now, some of you may ask, what about Land crayfish in the genus Engaeus?
It is true that there are a few species that can live mostly on land. They are often called ‘Land yabbies’. Nonetheless, even these unique creatures require water and moisture.
They build burrows down to 10 inches (25 cm) deep at the level of the nearest water table. It allows water to fill their small chambers at the bottom of the branching burrowing system.
As we can see, even these so-called land crayfish species require water to survive.
How Much Water Do Crayfish Need in an Aquarium?
Crayfish are classified as bottom-feeders/ scavengers. They stay well below the surface, near the bottom. Therefore, water should be at least deep enough to fully enter it.
Nonetheless, for optimal results, crayfish need more water volume. So, any filled aquarium will be good for them. Just make sure that you have an aerator in the tank to oxygenate the water for the crayfish.
You can also make some perches above the water line accessible to them in case of emergency. So, they will be able to come to the surface to breathe if needed.
In crayfish, gills are breathing structures that allow them to exchange oxygen and CO2 with surrounding water. Their gills are located inside the branchial chambers beneath the carapace and are attached to the bases of both the claws and walking legs.
Under optimal conditions (enough oxygen saturation), crayfish do not need land, they will be perfectly happy in the water environment. So, if you keep them as a pet, it is not required to keep them in paludarium setups, they will be absolutely fine in aquariums.