What is the primary target of Praziquantel in parasites?

Praziquantel primarily targets the membranes of parasites by increasing their permeability to calcium ions. This mechanism is critical for its anthelmintic action, as the influx of calcium disrupts the normal muscle function in the trematodes (flukes) and cestodes (tapeworms) that it targets. The increased calcium levels lead to a contraction of the parasite's muscles followed by paralysis, making it more susceptible to host immune response and facilitating its removal from the host's body.

This action is particularly effective because trematodes and cestodes generally rely on normal calcium ion homeostasis to maintain their muscular functions and overall viability. Consequently, disrupting this balance results in significant physiological distress for the parasites, ultimately leading to their death.

Other options might suggest potential action points for various drugs, but they do not accurately reflect the mechanism by which praziquantel operates. For instance, while glycolysis pathways, fatty acid biosynthesis, and neurotransmitter receptors are important to various aspects of parasite metabolism and function, they are not the specific targets for praziquantel. Instead, the drug's efficacy hinges on its unique ability to manipulate calcium ion dynamics within the parasite, making option B the best choice.