"what's on my fish" ?


Lernaea species, commonly known as “anchorworms,” are crustacean, copepod parasites that can infect and cause disease & mortality in many types of freshwater fishes, especially wild-caught and pond-raised species.

Infestations with Lernaea are most prevalent in the summer months and occur more commonly in stagnant or slow-moving water bodies. Approximately 110 species of lernaeids (Lernaea and Lernaea-like parasites) have been described.

Lernaea Coprinaceae, one of the more common species, is found worldwide. It is most common in cyprinids, including koi, common carp, and goldfish; however, it can infect other species of fish and has caused major kills in Arkansas catfish in ponds that were also stocked with bighead carp.

Lernaea has also been reported to infect amphibians

Anchor Worm Life Cycle Because Lernaea is a copepod and crustacean, it is related to crabs, lobsters, and shrimp, all of which have a multi-stage life cycle Lernaea is unusual, however, as most common copepod species are free-living and do not cause disease.

Although organisms belonging to this group have complex life cycles, they do not need to pass through an intermediate host; rather they can spread directly from fish to fish.

This direct life cycle can take from 18 to 25 days to complete, and only a fish (or an amphibian) is necessary for the organism to develop from egg to mature adult.

The Anchor worm life cycle is similar whether the host is a fish or amphibian, different life stages during development live on and off the fish.

After a male and female parasite mate, the male dies and the female bores into the host tissue, eventually using a large anchor on her anterior (“head”).

To Permanently embed into the skin and muscle of the fish The female matures into an adult and, within 24 hours, may begin to release eggs from a pair of sacs on its posterior (“back”) end.

Each released egg hatches within 24–36 hours. Females are very prolific and can produce batches of up to 250 juveniles (nauplii) every two weeks for up to 16 weeks at temperatures warmer than 25°C.

Newly hatched nauplii are free-living (not parasitic) and develop through three different naupliar stages in about 4 days.

At that point, they moult into the first copepodid stage, become parasitic, and attach to a host, often on the gills.

Over the next 7 days, the parasite develops through five different “copepodid” stages. The copepodid stages typically are also found on the gills but are not permanently embedded in the tissue.

Once in the final copepodid stage, the male detaches, but the female remains parasitic, attached to the current host or moving to another fish.

Adult males die within 24 hours. In one study, the entire life cycle took approximately 18–25 days when fish were held at 29°C. The optimal temperature range for Lernaea is 26–28°C.

If Temperatures fall below 20°C, juvenile Lernaea is unable to complete their development, and at 14°C, females will not reproduce. However, adult females can overwinter on the fish host, producing eggs when water temperatures warm up in the spring