Talking about male/ female crabs and how the horseshoe eggs come to be can be interesting and sometimes awkward depending on the audience.
Unlike the male fiddler crabs that have the large claw to attract females, male horseshoe crabs mate a completely different way.
As mentioned briefly before, females are usually larger and males smaller. This is the first clue in identification. If this is not clear, the next best way to identify the crab, if at all possible, is through their legs.
Horseshoe crabs have six sets of legs. Only the back five are used for them to walk and to eat. The front set, closest to the top of the shell or carapace, are called pedipalps, palps, or palpi. Pedi comes from the Latin for “foot” and palp from the Latin for “touching”. On the females, these look like their walking legs. On the males, they can be described as looking like mittens, boxing gloves, large claws, or large pincers.
Females give off pheromones to attract the males when they, the females, arrive on shore. The males are usually waiting for the females to come up.
The males use these pedipalps to hold onto the back of the female crab on an area known as the opisthosoma. This is the back part of the crab right before the telson. They hang on very tightly. Waiting.
If you, the reader, ever have the chance to observe the horseshoe crabs mating, watch carefully. They are silent and strong and follow along with the currents one may or may not be aware of.
More than one male horseshoe crab can follow and fertilize just one female’s eggs. One female can lay an estimated 9,000 to 90,000 eggs. She may lay them in one hole or may create more than one hole. The male or males follow along, attached or not, to fertilize the eggs.
Once the female lays her eggs, the eggs will be on their own. The female leaves.
Most people find it shocking that the horseshoe crabs would go through all of this trouble and then leave their eggs. Yet if one thinks about it, they are not the only species that do this. The animals humans look to like frogs, turtles, and fish do this as well.