How can you tell if my Hermit Crab is a boy or a girl?
This is a million dollar question? This is a question often asked and difficult to answer. But there is a way.
Many long time owners and a hand full of scientist believe they can change their sex, as need be, when they need to reproduce. This has not been proven. This is what happens with worms. And hermit crabs are not in the worm species.
Some believe it has to do with the size of the claw but actually different species have different types of claws and different colors and this is not sex related. The shape of the claw is a good way to recognize a particular species. For instance Caribbean and Floridian Hermits have a deep purple claw, Haiti Hermits have an orange - purple claw, Ecuadorian have a tan - brownish - orangish claw often mostly tan (but it can vary), Philippine hermits have a smaller more purple claw and Tahiti and Hawaiian hermits have a black or white claw depending on the island.
Since they seldom come out of their shell it is difficult to see a difference from the body prospective.
It has been noticed that the females with the egg pouches found in the spring do not have hairy legs, where the males of the same size do. They do have long hair near they abdomen where the long hair helps hold the eggs but you usually can not see it.
Regardless they do not breed in captivity and they have NEVER been able to recreate the environment that they need to reproduce. Many studies have tried. All have failed to my knowledge.
The way recognized by many who have been picking and selling hermits for years say the female has smoother legs and the male has very hairy legs. You can see this only after they are the size of at least a golf ball.
If you just have to know then there is some thought that the female land hermit crab has tiny genital openings called gonopores. Gonopores are located on the first segment on the back pair of walking legs. They are near the joint of the cephalothorax and abdomen very close to the body. Only to female crab has them.
They are opening into which the male crab places his spermatophore during mating. The male crab encourages her to come out of her shell, gently tapping and rocking the female crab. The crabs mate in a position where the female's gonopores line up with male's fifth pair of legs. All speicies sold in the US produce the same way.
Because most crabs are reluctant to come far enough out of their shells and allow you to see whether or not they are male or female, please do not force them.
Do we really know for sure? I don't know but I believe the hairy leg story. After all with a little help, it is true in the human species.
If you happen to miss name your hermit by sex. Don't worry they do not mind.
Anatomy of a Hermit Crab (provided by: Crustacean Lab, Museum Victoria, Australia)
In terms of lifestyle there are two distinctly different types of anomurans: false crabs which look and behave similarly to true crabs (Brachyura) and hermit crabs which live in shells. But they are similar anatomically in having the fifth leg much smaller than the other walking legs. In false crabs three pairs of legs are used for walking and in hermit crabs two pairs extend from the shell to move it and its inhabitant about. The abdomen of false crabs is tucked under the body as it is in brachyuran true crabs. Hermit crabs are rarely seen out of the gastropod shells they inhabit. As would be expected their body structure is modified to their lifestyle. All hermit crabs have a twisted soft abdomen protected by an empty shell into which the animal can retreat when threatened. The strong claws of the crab to protect the rest of the body close the opening to the shell and the animal can be almost impossible to dislodge. As the hermit crab grows, it must find a larger shell and in some dense populations, fighting for shells is a frequent event.
Like true crabs, female false crabs usually lay their eggs shortly after copulating but can also store sperm for many months. The eggs are fertilized as they are laid by passing through the chamber holding the sperm. Eggs are carried and brooded in a mass attached to the abdomen. In the case of hermit crabs this is inside the shell. The number of eggs is usually large but depends on the size of the crab. Once developed the egg hatches into a zoea which usually swims off to begin life in the plankton. There it goes through several molts as it grows and develops. Eventually the final larval stage will settle on the sea floor before transforming to a juvenile crab.