Which parasite completes its life cycle on or in its host, often requiring no intermediate host?

Which parasite completes its life cycle on or in its host, often requiring no intermediate host?

• A. Gasterophilus species
• B. Otodectes species
• C. Hypoderma species
• D. Cuterebra species

Answer: (B)

The concept being tested is whether a parasite can complete its entire life cycle on or in the same host without needing an intermediate host or an environmental stage. Otodectes cynotis fits this pattern because its entire life cycle occurs in the host’s ear canal: eggs hatch into larvae, molt to nymphs, and become adults, all on the host. No intermediate host or outside environment is required for development. The other parasites involve stages outside the host. Gasterophilus species lay eggs on the animal and larvae develop in the stomach, but they must pass out to the environment to pupate, so an external stage is needed. Hypoderma and Cuterebra species also rely on life-cycle stages that leave the host and develop in the environment (soil) before completing maturation. Thus, the parasite that completes its life cycle on or in its host is Otodectes species.

The concept being tested is whether a parasite can complete its entire life cycle on or in the same host without needing an intermediate host or an environmental stage. Otodectes cynotis fits this pattern because its entire life cycle occurs in the host’s ear canal: eggs hatch into larvae, molt to nymphs, and become adults, all on the host. No intermediate host or outside environment is required for development.

The other parasites involve stages outside the host. Gasterophilus species lay eggs on the animal and larvae develop in the stomach, but they must pass out to the environment to pupate, so an external stage is needed. Hypoderma and Cuterebra species also rely on life-cycle stages that leave the host and develop in the environment (soil) before completing maturation. Thus, the parasite that completes its life cycle on or in its host is Otodectes species.