Crabs are fascinating creatures with their signature claws and ability to be both in and out of water. If you go to the beach, you’re more than likely to see them crawling in and around tidal pools, and it may leave you wondering, can crabs live out of water?
There are terrestrial crabs that can live almost entirely on land, and aquatic crabs live in and around water but can only survive up to a few days without it. Terrestrial crabs also have gills, like underwater crabs, that still need moisture for their survival on land.
It’s incredible how a crab can adjust from breathing underwater to breathing on land, making crabs unique! Whether they live in the water or above it, crabs have mechanisms to live in either of these conditions, which we can tell you all about, along with other interesting facts about these crustaceous creatures.
How Crabs Live Out Of Water
Crabs can live on land! Who knew? Terrestrial crabs, the ones that live on land, have adaptions meaning they don’t need to be in the water but also have gills that require moisture. Crabs that live in water, known as aquatic crabs, also have special adaptions to survive without water for a few hours or days.
How Crabs Breathe In And Out Of Water
Before diving into how terrestrial and aquatic crabs survive above water, it is helpful to know the science behind how they breathe. All real crabs possess gills that obtain oxygen from the water filtering through them. The oxygen gets distributed through a crab’s bloodstream, and carbon dioxide is collected and expelled through its mouth, which is why you sometimes see crabs blowing bubbles!
Crabs That Live Out Of Water
Terrestrial crabs, also called land crabs, like the Coconut Crab or Land Hermit Crab, don’t spend much time in the water as they would die if submerged for too long. Their gills are not capable of being underwater for long periods.
A terrestrial crab’s gills store water to keep them moist to maintain their breathing. They have unique plates by their gills that can close to keep moisture from escaping. These crabs also reserve water in their blood, bladder, and compartments around their body. They also have a biological modification of gills with a smaller surface area to prevent water from evaporating too quickly.
Terrestrial crabs also take up water by drinking dew and other groundwater. A terrestrial crab’s behavior also helps them retain their water, which entails finding hiding places that are cold, shady, and contain moisture. This behavior helps stop water from drying up and doubles as a protection from predators!
Did you know that terrestrial crabs can travel many miles inland? Some species can even be found up to 5 miles away from a body of water! Although these crawling terrestrial creatures can live a long time away from H2O, most crab species need to return to the water for breeding purposes.
How Aquatic Crabs Survive Out Of Water
Aquatic crabs also enjoy being on land, some around tidal pools at the beach. Many sea crabs spend their time close to the shore, which may leave them stranded without water when the low tide sets in. Being stranded is why they need to be able to stay alive in those few waterless hours.
To survive above water, aquatic crabs have plates by their gills that shut to keep moisture for breathing purposes, just like terrestrial crabs. These water-loving crabs also behaviorally find a dark-lit damp spot to hide in and take water from puddles or dew.
All crabs with gills need oxygenated moisture in their gills to live. The main difference between aquatic and terrestrial crabs is that terrestrial crabs have evolved physically to survive without needing to be in the water.
Crabs That Can Live Entirely In Water
Since some crabs live on shorelines and need water to survive, these aquatic crabs can live entirely under the sea due to their physiology. Many species live deep in the ocean, like the Japanese Spider Crab, which is a whopping 15 inches long and 12 feet wide! Although some species on the shoreline can live permanently underwater, they behaviorally enjoy spending some of their time out and about!
Fun Facts About Crabs
Crabs are marvelous creatures with legs that walk sideways and intimidating claws. There is a lot to know about crabs and their behaviors. Crabs are just as fascinating as they look!
Since some crabs live above water, many studies have been conducted on terrestrial crabs because they draw scientists’ curiosity on evolution. After all, terrestrial crabs are slightly different from their aquatic counterparts. The differences between crabs of the land and those needing a body of water can give ideas on how life evolved from water to land habitation.
Male and female crabs identify by their body shape. Male crabs have triangular-shaped abdomens while a female’s body is large and rounder. Female crabs also mostly have smaller front claws than male crabs.
Why do crabs have claws? Crabs need them to cut and crush things, such as catching prey and slicing it small enough for them to eat. Crabs also use them like hands to feed themselves. They also use their claws to fight against other crabs and may sometimes lose one in a fight. Not to worry, they can grow back!
Crab’s eyes are at the end of stalks above their head, which allows them to see when they hide behind rocks or in the sand. These stalks can move in all directions and can retract if need be. The wide range of stalk motion helps them be safe from predators. A crab’s eyes see in pixels because their eyes have thousands of light sensors, each with a lens and cornea.
You might think that crabs can only walk sideways, but they can surprisingly walk in all directions! They mostly walk sideways because it is quicker and easier for them to move around that way.
Whether in the deep blue sea or crawling miles away from shore, all real crabs have gills that need a bit of oxygenated moisture to keep them alive. Both terrestrial and aquatic crabs have physical features and behavioral tendencies to keep their gills from drying out. Even though some species can live underwater permanently, they enjoy a bit of time on land.
Terrestrial crabs fascinate scientists due to their evolutionary qualities. Crabs also have different body shapes that can identify whether they’re male or female, claws that can regrow, eyes that move around on stalks above their head, and an ability to walk in all directions. When you see a crab, you’ll know just how intricate and incredible these creatures are!