Hermit crabs rarely reproduce in captivity, meaning owners rarely see the birth process. This is because hermit crabs rely on the presence of expansive bodies of saline water to birth their young. Away from the ocean, female hermit crabs lose interest in breeding.
Hermit crabs lay eggs, never birthing live young. After two wild hermit crabs mate, the female can carry up to 50,000 eggs. The female hermit crab carries these for about a month before laying them in the ocean. The eggs hatch upon contact with salt water.
Hermit crabs don’t play an active role in raising their young. After a female lays eggs in the sea, she moves on and seeks her next mate. The hatchlings are known as zoea, the first life stage of three that must be negotiated to evolve into a healthy adult hermit crab.
How Do Hermit Crabs Reproduce?
The breeding process involves a single male and female and the release of spermatozoa. Once sperm enters the female’s reproductive organs, known as the gonophores, she fertilizes and creates eggs.
Hermit Crab Mating
Hermit crab egg production involves mating, and courtship is the first step. The Journal of Crustacean Biology explains how females must accept a male’s invitation to mate; the process can’t be forced.
A female hermit crab in season releases distinctive pheromones that capture the attention of males. Male hermit crabs invite the female to breed by rapping on her shell.
Male hermit crabs often fight over who will mate with a female. A male that wishes to breed may also ‘guard’ a female, following her around to prevent access to other males.
If the female’s unreceptive to breeding, she hides in her shell until the male loses interest. She’ll emerge and instigate the breeding process if she wishes to mate.
Hermit crab breeding takes place within respective shells for the safety of both animals. A hermit crab’s penis measures roughly half its abdomen, so it can locate and enter a female’s gonophores – found above the rearmost legs – without leaving its shell.
Will My Captive Hermit Crabs Mate?
In most circumstances, pairing male and female animals in the same habitat creates a risk of breeding. This isn’t the case with hermit crabs, so they seldom mate in captivity.
Female hermit crabs still enter season while living in captivity, so males will attempt to mate. The female will reject advances and hide in her shell. Females move in and out of season every three or four days, and males lose interest as soon as the pheromones cease.
Keep an eye on your hermit crabs if you have males and females living together. Ensure your female hermit crabs aren’t anxious about male attention and prevent disputes over breeding rights.
What Do Hermit Crab Eggs Look Like?
Female hermit crabs carry eggs in a sac found on the side of the abdomen. If a female is fertilized, eggs will immediately become visible. As the eggs grow in size, they’ll become more prominent.
Hermit crabs are initially bright red, akin to a fire truck. As the female grows closer to laying her eggs, they start fading to a deep shade of gray.
Where Do Hermit Crabs Lay Their Eggs?
Hermit crabs lay their eggs in the ocean, which is why captive hermit crabs rarely mate. The female understands the difference between a bathtub of saline water and the sea, and the lack of expansive water makes breeding unappealing.
A female may lay her eggs on the spot if the tide is low. Terrestrial hermit crabs can only hold their breath for up to 30 minutes, so this may not be safe. If necessary, the female will toss her eggs into the sea from the shore or climb a tree and drop them into the ocean.
How Often Do Hermit Crabs Lay Eggs?
Hermit crabs can reproduce and lay eggs throughout their life. Females enter into season at least once a week, and it takes a month for eggs to develop and be ready for hatching.
This suggests that hermit crabs can lay at least ten egg clutches annually.
The lifespan of wild hermit crabs varies, but it could be as long as 30 years. A healthy female could lay over 300 clutches of eggs in her life.
How Many Eggs Do Hermit Crabs Lay?
Female hermit crabs can carry as many as 50,000 eggs in any single clutch, and it’s rare for a female to carry fewer than 1,000 eggs at any time. The male and female’s age, size, and fecundity will affect how many eggs are produced.
Hermit crabs can reproduce as soon as they reach adulthood. Larger females can carry more eggs than their smaller counterparts, so more eggs are produced as the hermit crab grows older and molts. The Journal of Natural History considers a size between 4.5 and 6 mm optimum for breeding.
While female hermit crabs prefer to mate with larger males, Proceedings of the Royal Society explains that smaller and more timid males are more fertile and likelier to produce larger clutches.
How Long Does it Take for Hermit Crab Eggs to Hatch?
A female carries eggs in her sac for around one month. Once she is ready to lay her eggs, she’ll move toward the ocean and do so. The eggs will hatch almost immediately upon contact with salt water.
If a female hermit crab in captivity carries eggs, she’ll avoid saltwater this month so that her eggs don’t hatch prematurely. Provide your hermit crab with fresh water for bathing instead.
What Happens When Hermit Crab Eggs Hatch?
Once hermit crab eggs are laid, the mother abandons the clutch. From this point, the hatchlings must survive three early life stages:
Stage One – Zoeae
When hermit crab eggs hatch, zoea emerge. Zoea are tiny larvae that rise to the top of the ocean, where they float alongside plankton.
Few hermit crab hatchlings survive beyond the zoea stage. Their diminutive size, and proximity to plankton, mean they’re usually eaten by passing fish and whales.
If the zoea remains alive for 30–60 days, it’ll consciously make its way to the shore. Upon reaching dry land, the zoea commences the next stage of evolution.
Stage Two – Megalopa
Megalopae live on the shore of the beach and are impossible to see without a magnifying glass. During this life stage, they start to resemble a hermit crab, though their appearance is comparable to a lobster.
Life expectancy for megalopae is short, rarely more than a few hours. They adopt a “survival of the fittest” philosophy, frequently cannibalizing each other for strength.
A megalopa will burrow under the sand if it makes it beyond this initial fight for survival. A megalopa will remain hidden for around 30 days and evolve into a hermit crab.
Stage Three – Juvenile
Juveniles are tiny hermit crabs. A juvenile hermit crab will emerge from the sand once its evolution from the megalopa phase is complete and seek a shell.
As juvenile hermit crabs lack shells and are so small, they’re vulnerable to predators. Unless the juvenile finds a shell for protection quickly, it is unlikely to survive. Most juvenile hermit crabs seek vacant gastropod shells, although a bottle cap can also be used.
In the earliest months of life, hermit crabs molt regularly. Every molt leads to an increase in size and a strengthening of the exoskeleton. Once a hermit crab reaches 3.5mm in length, it is an adult. An adult hermit crab will join a colony of conspecifics and seek to breed.
The life cycle from zoea to hermit crab is fraught with danger, and few hatchlings survive long enough to evolve. This is why hermit crabs lay so many eggs, and larger clutches provide a greater opportunity for the propagation of the species.
