Final answer:
Adult pentastomes infect the respiratory system of the host, not the digestive, cardiovascular, or mesenchymal tissues.
Step-by-step explanation:
Adult pentastomes are always associated with infecting the respiratory system of the host. These endoparasitic creatures are not related to the digestive, cardiovascular, or mesenchymal tissues, but rather they are typically found in the respiratory tracts of vertebrates. The lifecycle of a pentastome includes the release of eggs into the environment via the respiratory secretions or feces of the host where they are subsequently ingested by an intermediate host and eventually end up in the lungs of the definitive host after being transmitted through various means.
The endoderm, the innermost embryonic germ layer, gives rise to both the digestive system and the lower respiratory system, which is where the pentastome establishes its presence. Thus, it is crucial to recognize that these organisms are primarily associated with the respiratory tract and not with the other body systems mentioned in the options provided.