What organisms can penetrate the shell of the horseshoe crab?

Organisms that can penetrate the shell of the horseshoe crab include certain species of predatory sea stars, gastropods like moon snails, and some types of crabs. These predators have specialized adaptations, such as strong beaks or appendages, that enable them to break through the horseshoe crab's tough exoskeleton. Additionally, some parasitic organisms, like certain types of barnacles and flatworms, can also invade the horseshoe crab's body.