In which host do adulthood and mating of helminths occur?

The definitive host is the organism in which the adult form of a helminth (a type of parasitic worm) develops and where the mating and reproduction take place. In the life cycle of helminths, the definitive host is crucial because it harbors the mature form of the parasite that can reproduce sexually.

For example, in the case of tapeworms, the definitive host is typically a vertebrate, such as a human or other animals, where the tapeworm can grow to its adult size, mate, and produce eggs. The eggs are then excreted from the definitive host into the environment, allowing the cycle to continue.

In contrast, the intermediate host is where the larval stages develop, and they do not reach adulthood or reproduce. The paratenic host merely serves as a transportation vehicle without any further development of the helminths. An accidental host, on the other hand, is an organism that is not part of the typical life cycle but may become infected due to unusual circumstances. Thus, the definitive host is distinctly characterized as the stage where maturity and reproduction occur for helminths.