Question

Thelazia californiensis has an indirect life cycle that is assisted by the fly which ingests the ova that was laid in the tears. The ova then molts to L3 within the fly and is then passed to the definitive host when the fly lands on the definitive host to feed.

Answer 1

Parasitic organisms like Thelazia californiensis and others possess intricate life cycles incorporating different developmental stages and intermediate/definitive hosts to ensure their propagation and survival within ecosystems.

Step-by-step explanation:

Life Cycles of Parasites

The life cycles of parasites are often complex and involve multiple hosts and developmental stages. Thelazia californiensis participates in an indirect life cycle with the fly acting as an intermediate host, where the ova molts to the L3 stage, which is the infective stage for the definitive host. Similarly, other parasites such as Loa loa, T. gondii, Schistosoma spp., and Strongyloides stercoralis have complicated life cycles that include various stages and different mechanisms of host infection and transmission. The Loa loa parasite is transmitted between humans by deerflies, while T. gondii involves cats as the definitive host and may alter intermediate host behavior. Schistosoma species require water snails as secondary hosts and are transmitted through contact with contaminated water, while Strongyloides stercoralis is a soil-transmitted helminth that can penetrate the skin. These intricate life cycles facilitate the spread and sustainability of these organisms within their respective ecosystems.