Final answer:
The life cycle of a fluke involves alternating between primary (often a vertebrate) and secondary hosts (usually mollusks). In the primary host, the fluke matures and reproduces, while in the secondary host, it multiplies asexually. This complex life cycle enables the fluke to spread and persist through various hosts.
Step-by-step explanation:
The life cycle of a fluke, specifically the sheep liver fluke, is complex and involves multiple hosts. Flukes, or trematodes, are parasitic flatworms with life cycles that entail both sexual and asexual reproduction. A typical fluke life cycle includes a primary host where sexual reproduction occurs, often a vertebrate like sheep for the liver fluke, and secondary hosts, almost always mollusks, where asexual reproduction takes place.
During its life cycle, the liver fluke first resides in a mollusk, where it multiplies asexually. The larval forms are then released and must find a vertebrate host to mature. When they infect their vertebrate host, they make their way to the liver, becoming adult flukes. These adults lay eggs, which exit the host and hatch into larvae upon reaching water, thereby infecting new mollusk hosts. The cycle is designed to spread across different hosts, increasing the chances of survival and propagation of the species.
In the case of human fluke infections such as schistosomiasis, caused by blood flukes of the genus Schistosoma, the larvae penetrate human skin when an individual enters contaminated water. After entering the body, they migrate to various organs, potentially causing severe health issues.