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The Hermit Crab Life Cycle (Details of Each Stage)

The Hermit Crab Life Cycle (Details of Each Stage)

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The purpose of this blog is to share general information and is written to the author's best knowledge. It is not intended to be used in place of veterinary advice. For health concerns, please seek proper veterinary care. In addition, as an Amazon Associate I earn from qualifying purchases.

If you are new to having a hermit crab as a pet, you are probably not that familiar with their life cycle. Hermit crabs are omnivores and love to scavenge clams and bits of dead animals.

For such small creatures, they are fascinating. I became interested in the life cycle of hermit crabs when one of my friends got one as a pet.

The life cycle of a hermit crab starts with the mother, who will carry the eggs for 30 days. Then she will empty them in the ocean when the tide is high. After the eggs have hatched, they enter the protozoa stage, then the megalopa stage, and lastly, the juvenile hermit crab will emerge.

Hermit crabs have a complicated life cycle. There are over 1200 species of hermit crabs, with only one living in freshwater. Hermit crabs are most closely related to lobsters.

I thought I would do more research on the life cycle of the hermit crab and share the information I found in this post.

The Hermit Crab Life Cycle

Holding a Baby Hermit Crab

Hermit crabs can be aquatic or terrestrial (land-dwelling); in this post, we will be looking at the life cycle of both of these hermit crabs. They don’t grow the shells they live in but appropriate the discarded shells of moon snails. While there are well over 1,000 hermit crab species, and their life cycles are almost identical, they differ in color.

The ocean-dwelling hermit crab will have stripes on its appendages, and the land hermit crabs won’t. Hermit crabs have been seen in green and blue to red, yellow, orange, pink, and brown.

The Beginnings

Even though the aquatic and terrestrial hermit crabs are different species, they have similar life cycles. When a terrestrial and aquatic hermit carb mate, the female hermit crab will lay thousands of eggs.

The female hermit crab holds these eggs on the left side of their abdomen called the pleopods. She cares for the eggs and keeps them on the pleopods for about thirty days while they mature. The female will stay away from saltwater during this time because saltwater triggers the eggs to hatch.

As the eggs grow, they will live off of the yolks in the eggs. The eggs will turn from brick red to a dull grey as they deplete the yokes. When they have all turned grey, they are ready to hatch.

As soon as the eggs are ready to hatch, the female hermit crab will travel to the ocean when there is a high tide. She will then submerse herself in the water and lay or fling the eggs in the high tide. The moment the eggs hit the water, they will start to hatch.

The Early Growing Phase

While the hermit crab is still larva during the nauplius stage, it is still in the egg, and it has three pairs of legs, one eye, and its body is unsegmented. The next part of the hermit crabs life cycle in the egg is called the protozoa stage and lasts from the egg stage to just after the hermit crab has hatched.

After it has hatched, the nauplius crab enters the zoea stage. In the zoea stage, the hermit crab has rudimentary legs on its thorax and abdomen and at least one spine on its back. All zoea go through 4-6 growing stages, lasting between 40-60 days. During this time, the zoea is tiny and plankton-like and floats around with other crustaceans like shrimps.

As it grows, the zoea develops more. In the megalopa, the zoea’s last growing stage looks a lot like a smaller version of an adult hermit crab or lobster. This stage lasts about 30 days.

During the megalopa stage, it will look for its first shell. The terrestrial hermit crab will now be spending more time on land than in the ocean. After the megalopa finds its first shell, it will bury itself in the sand to undergo a metamorphosis and emerge as a juvenile hermit crab.

The Adult Stage

A Large Hermit Crab

The metamorphosis that the old megalopa goes through will change the gills of the juvenile hermit crab so it will be able to breathe air; it won’t be able to breathe underwater anymore. The hermit crab takes about a month to go from the megalopa to the juvenile hermit carb.

The juvenile hermit crab will need to molt at least once a month as it grows into an adult. During this time, it will need a new shell with each molt to accommodate its growing abdomen.

Most hermit crabs will wait for another hermit crab to start molting and steal the shell it leaves behind. Hermit crabs are very particular about the shells they choose, and they will inspect every aspect of the new shell to see it meets with approval before moving in.

As the hermit crab gets older, it will have the urge to mate, and while terrestrial hermit crabs live on land, they breed/reproduce in water. Hermit crabs travel to the ocean to find a mate, reproduce and release eggs. It’s a repeating cycle leading to the new generation of hermit crabs.

The journey from egg to an adult hermit crab takes around 4 – 5 months, and sadly a lot of the hatched hermit crabs will not make it to adulthood. In the wild, they are food to fish and other predators.

Hermit crabs can live over 40 years in the wild, but their life span drops dramatically with domesticated hermit crabs. The hermit crabs that live in captivity, which we keep as pets, only live between 10-15 years.

The Molting Stages

Hermit crabs go through molting stages throughout their lives. They can also go into hibernation, and the signs are very similar. So what are the differences between molting and hibernation?

When a hermit crab molts, it sheds its exoskeleton and grows a bigger one. After it’s done growing its new exoskeleton, it will eat the old exoskeleton. It reabsorbs the calcium left behind in the old exoskeleton, helping it recover quicker. It can take between two-three months for a hermit crab to fully molt. They will molt a couple of times a year, but younger hermit crabs molt more often.

The hermit crab will not move much after molting; there are a few reasons for this:

  • The hermit crab is waiting for the new bigger exoskeleton to grow harder.
  • The hermit crab is waiting for the muscles in its new exoskeleton to regain functionality.
  • Growing a new exoskeleton takes a lot of energy, and it needs to replenish its strength.

Before a hermit crab starts a molting stage, it will store water and nutrients in a sack on its body. It’s more visible in older hermit crabs. There are a few typical signs you can look for that indicate your hermit crab is about to molt:

Excessive Digging

When molting, a hermit crab is at its most vulnerable and will constantly dig to find the perfect place to bury itself. It needs to bury itself as deep as possible because the molting hormone (MH) is only released in complete darkness.

That is why it is essential to have a deep substrate in your crab’s aquarium. If you have more than one hermit crab in your aquarium, you must separate the one about to molt and give it its own tank to molt in peace. Molting is very stressful, and if other crabs or critters disturb it during its molting, it might not survive.

Food Gathering

As soon as a hermit crab is ready to molt, it will gather food and water because it won’t come out from underneath the substrate until it is finished molting, so it needs all that stored food. As mentioned earlier, it will hold the food in a sack to have food and water close by when it needs it.

It Will Be Less Active

Gray Hermit Crab in Shell

A hermit crab about to molt will get less active as the molting cycle draws near. They will stay buried for extended periods and eventually won’t come up for food when the molting is in full swing.

The Physical Appearance

There are changes in physical appearance you can look out for when your hermit crab is about to molt.

  • Its eyes will turn dull and white as the exoskeleton begins to separate from the stalks of the eye.
  • Their exoskeleton will turn a dull grey color when hermit crabs are about to molt.
  • If your hermit crab has lost an appendage, a new limb nub will form just before the crab starts to molt. It will regrow this limb during its molting cycle.

The Differences Between Molting and Hibernating Hermit Crab

Molting and hibernating look alike, but while molting is natural, hibernation can kill your hermit crab. Below are a few ways to can tell the difference before it’s too late.

  • If the temperatures drop suddenly below 70F in the tank, your hermit crab will bury itself and start hibernating; it won’t gather food like it would before molting.
  • Its exoskeleton will not turn a grey color.
  • A hermit crab about to molt will do so in average temperatures, not cold temperatures.
  • Hermit crabs that hibernate will not come up for food or water at all; that’s one of the reasons it’s so dangerous.
  • When hermit crabs are about to molt, they will sometimes find a smaller shell as their shell might let too much sand in during this time.
  • Hermit crabs in hibernation will not move and stay still, while molting hermit crabs will still show some movement.

Do Hermit Crabs Go Through Hibernation?

Hermit crabs go through different growth spurts during their life, and some of these stages include torpor, a mild hibernation. Hermit crabs will hibernate when the temperatures surrounding them drop below 70F.

Hermit crabs should not go into true hibernation. Invertebrates like hermit crabs are ectothermic (cold-blooded) and can’t regulate their body temperature. So if the temperature in its habit drops below 70F, it will go into hibernation to wait for the surrounding temperature to rise.

Because they rely on the temperatures of their surroundings to keep them warm, you need to ensure the temperature of their enclosure stays above 70F. If it stays below this temperature, your hermit crab won’t be able to digest any food, and it won’t be able to move much.

If you see your hermit crab keeps burying itself and won’t eat, you need to check on the enclosure temperature. Your hermit crab could die if the temperature doesn’t rise higher than 70F.

Interesting Facts About the Hermit Crab Life Cycle

There is a lot of fascinating yet exciting information about hermit crabs. I thought I would share some random facts about the life cycles of hermit crabs.

  • Hermit crabs that live in freshwater don’t mate because the eggs only hatch in saltwater, so captive hermit crabs will never reproduce because they are not near the ocean.
  • Saltwater aquatic hermit crabs (marine hermit crabs) are the most common; the one land (terrestrial) hermit crab is only found in Florida. It’s important to know what kind of hermit crab you have.
  • The older hermit crabs get, the less it will molt.
  • Hermit crabs can grow to weigh around 3 pounds, but one species called the coconut crab is the biggest hermit crab species and can grow 40 inches and weigh a whopping 10 pounds.
  • Hermit crabs need bigger shells each time they molt.
  • When hermit crabs find a new shell, they will sometimes line up to see who fits in the new shell.

Final Thoughts

A hermit crab’s life cycle is fascinating. Hermit crabs go through multiple stages of growth in their life, including the molting stages.

Molting is a constant in any hermit crabs life and only lessens as it ages. Hibernation is very dangerous for hermit crabs, and you should not mistake it for molting. It could lead to your hermit crabs’ death.

With meticulous care, a hermit crab can live up to 15 years in captivity, but a hermit crab can live to over 40 years in the wild. I had a lot of fun learning more about this fantastic critter.

Remember to check the temperatures of your hermit crabs tank every day and isolate it when it’s molting.

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