Lernaea

Lernaea is a genus of parasitic copepods in the family Lernaeidae, commonly known as anchor worms. Species of Lernaea parasitize a wide range of freshwater fish worldwide and are a concern in aquaculture, pet trade, and aquarium settings due to their impact on fish health and growth.

Morphology and life cycle. The adult female Lernaea attaches to a fish host by a large anterior holdfast that becomes embedded in the host tissue. A long, threadlike posterior stalk extends from the host and contains the reproductive organs. The male is free-swimming and much smaller. The life cycle includes free-living larval stages (nauplius and copepodid) that develop in the water, and a parasitic phase in which the female attaches to a host and releases larvae to seek new hosts. Progeny emerge to continue the cycle, facilitating spread within a population.

Hosts and signs. Lernaea species infect a broad range of freshwater fish and can occasionally be found in brackish environments. Infected fish exhibit irritation and rubbing against surfaces, flashing, and skin ulcers or hemorrhages at the attachment site. Heavy infestations can cause reduced growth, osmoregulatory stress, secondary infections, and increased mortality.

Diagnosis and management. Diagnosis is based on observation of the protruding anchor-like structure attached to the fish. Management typically involves removing the visible protruding female manually when feasible, followed by treatment of the water with approved antiparasitic products under veterinary or occupational guidance. Additional measures include quarantine and careful tank hygiene to prevent reinfection and monitor for new cases.

Prevention. Effective prevention includes quarantining new fish, inspecting for signs of anchor worms before introduction, maintaining good water quality, avoiding overcrowding, and promptly addressing any signs of parasitic infection.