monogenid

Monogenids are a class of parasitic flatworms belonging to the phylum Platyhelminthes. They are commonly found as external parasites on fish and other aquatic animals, although some species can also infect amphibians and reptiles. Unlike other flatworms, monogenids have a relatively simple life cycle, typically involving a single host. They reproduce sexually, and the larval stage, known as an oncomiracidium, is free-swimming and infects a new host.

Monogenids attach to their hosts using a specialized posterior attachment organ called an opisthaptor. This structure is often complex and armed with hooks and suckers, allowing the parasite to firmly anchor itself to the host's skin, gills, or fins. Feeding typically involves rasping at the host's tissues or consuming mucus and blood.

While many monogenid infections are asymptomatic, heavy infestations can cause significant damage to the host. This can lead to respiratory distress, particularly if the parasites are attached to the gills, and can result in secondary bacterial or fungal infections. In aquaculture, monogenid outbreaks can cause substantial economic losses due to increased mortality and reduced growth rates in farmed fish. Identification and treatment of monogenid infections often involve microscopic examination of the host and the use of specific antiparasitic drugs.