Invasion History

First Non-native North American Tidal Record: 1948
First Non-native West Coast Tidal Record: 1948
First Non-native East/Gulf Coast Tidal Record: 1978

General Invasion History:

Lernaea cyprinacea was first described from Europe in 1745 under a trinomial name, and was redescribed by Linnaeus in 1758 (Kabata 1979). This freshwater parasitic copepod infects a wide range of teleost fish (100+ species) and also amphibians (Hoffman 1967; Kabata 1979). Consequently, it has been widely spread throughout most of the world with ornamental and stocked fishes. Stocks and escapes of Carassius auratus (Goldfish) and Cyprinus carpio (Common Carp) may be the most likely vectors (Hoffman 1967; Tidd 1934). It is probably native to Asia, including Japan, and has been introduced to mainland Europe, the British Isles, Africa, Australia, North America, and South America (Hall 1983; Hoffman 1967; Kabata 1979; Kennedy 1993).

Lernaea cyprinacea was first reported (as L. carassii) in North America from goldfish farms in Ohio (1929) and Indiana (Tidd 1934). Wilson (1918) mentioned it in a global survey of the genus, but did not report it from this continent. Tidd (1934) notes: 'If Lernaea carassii were a species native to the United States, it seems strange that it could have so long escaped the attention of fanciers of ornamental fish and fisheries biologists. While at present I have records for the occurrence of the 'anchor parasite' in Ohio and Indiana only, I would not be surprised to find that it already has a wide distribution range'. Even at this early date, L. cyprinacea was already known from nine species of fishes (Tidd 1934). Hoffman (1967) cited records from 11 states, including many midwestern states, and Maryland, California, Washington, and Arizona. A search of recent citations adds 10 states to this list, so L. cyprinacea is probably found in most of North America. Records from estuaries are spotty, probably because few surveys of freshwater fish parasites have been conducted in tidal waters. This parasite is likely to occur in most tidal fresh waters in temperate North America.

North American Invasion History:

Invasion History on the West Coast:

In the Columbia River system, Lernaea cyprinacea was found in Lake Oswego, Oregon, adjacent to the tidal Willamette River, above Portland, on Oncorhychus tshawytscha (Chinook Salmon) and in Tigard, Oregon, in a small private pond, on Oncorhychus mykiss (Rainbow Trout) (both in 1948, Uzman and Rayner 1958). In the non-tidal watershed, it was found in the lower Yakima River on four species of introduced fishes and four species of native fishes in 1957 (Uzman and Rayner 1958).

In the San Francisco Bay estuary, L. cyprinacea was collected at the Fish screen facility in Tracy, California in the Sacramento-San Joaquin Delta during a survey of fish parasites in 1973. It was found on introduced Ameiurus catus (White Catfish) and four native fishes Mylopharodon conocephalus (Hardhead); Orthodon microlepidotus (Sacramento Blackfish); Pogonichthys macrolepidotus (Splittail); and Ptychocheilus grandis (Sacramento Squawfish) (Hensley and Nahhas 1975).

Invasion History on the East Coast:

Lernaea cyprinacea was listed as a fish parasite in the Coastal Zone of South Carolina, from White Catfish (Amieurus catus) (Lawler 1978). It is probably widespread in fresh and low-salinity zones of many East and Gulf Coast estuaries. We did not find records from tidal waters of Chesapeake Bay, but it was abundant in a pond in College Park, Maryland (Haley and Winn 1959) and in the Susquehanna River in central Pennsylvania (Deutsch 1977; 1978; and 1984), affecting at least 18 species of native and introduced fishes.

Invasion History Elsewhere in the World:

Lernaea cyprinacea may have been introduced to Western Europe with Common Carp (Cyprinus carpio) in Roman times, or later with Goldfish (Carassius auratus). However, it was not reported from England until 1960 (Kennedy 1993) and in the Ebro River system, Spain it was first reported in 1995 (Oscoz et al. 2009), so it may still be extending its range.

In Africa, it was found in Lake Victoria by 1956, and was widespread in South Africa by the 1990s (Robinson and Avenant-Oldewage 1996). It was present in Australia by the 1970s (Hall 1983; Marina et al. 2008) and Brazil by the 1980s (Maghalaes 2006). In each case, it spread rapidly onto native fishes.


Lernaea cyprinacea is an ectoparasitic copepod, whose adult females normally parasitize freshwater fishes, but occasionally attack amphibians. The free-swimming opepodites, the adult male, and the pre-attachment female are somewhat like that of a cyclopoid copepod. The adult female metamorphoses after attachment to a host and becomes highly modified, with the cephalothorax expanded laterally into 2 pairs of horns (part of its holdfast) and a wormlike, elongated thoracic portion, with 3 pairs of vestigial swimming legs along its length. At the end of the thorax is a pregenital swelling, anterior to the oviducts, where paired egg-sacs are attached. There is a short, conical abdomen, usually at an angle to the rest of the body, ending in pair of hair-like caudal rami. The lateral horns and long body give rise to the name 'anchor-worm'. The horns are derived from the maxillipeds and 1st swimming legs. They are quite variable in shape, with the dorsal pair much larger than the ventral, divided into two branches, some distance from their bases. The ventral pair is slender, and usually simple. The overall length of the attached female is 10-20 mm. Description based on: Tidd 1930; Demaree 1967; Kabata 1979; and Robinson and Avenant-Oldewage 1996.

Pre-attachment females and males are similar in general body shape. The cephalothorax is shield-shaped, with a rounded anterior and parallel sides. A U-shaped groove divides the head from the 1st leg-bearing segment. There are five thoracic segments, and a urosome consisting of 4 segments. Overall, the female body tapers uniformly – the 1st urosome (genital) segment is about the same width as the 5th thoracic segment. The small, tapered, caudal rami have small lateral setae and single long terminal setae. The antennules (1st antennae) are uniramous, with 6 segments. Pre-attachment females are 1.2-1.4 mm long (Kabata 1979).

Male L. cyprinacea have a narrower urosome and genital segment than the female. The antennules have 8 segments. They are smaller than the pre-metamorphosis females, about 1.1 mm in size (Grabda 1963; Kabata 1979). After hatching, this copepod goes through 3 nauplius stages, and 5 copedite stages, before molting into a 'cyclopoid' adult stage (Grabda 1963). This is the final development stage for males, but females go through a radical transformation into a wormlike form, after attachment to a host, usually a fish, but sometimes a frog (Grabda 1963; Kabata 1979).

The taxonomy of this copepod is complex, because the morphology of the attachment structures varies greatly in the adult female according to the site of attachment, the shape and behavior of the host, and the surrounding environment (Kabata 1979).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Maxillopoda
Subclass:   Copepoda
Order:   Caligoida
Family:   Lernaeidae
Genus:   Lernaea
Species:   cyprinacea


Lernaea carassii (Tidd, 1933)
Lernaea elegans (None, None)
Lernaea esocina (Burmeister, 1835)
Lernaea ranae (Stunkard & Cable, 1931)
Lernaea tentaculis quattor (Linnaeus, 1758)
Lernaeocera cyprinacea (Blainville, 1822)
Lernaeocera gasterostei (Bruhl, 1860)

Potentially Misidentified Species

Lernaea anomala
On Micropterus spp., North Carolina, Louisiana

Lernaea cruciata
On Ambloplites rupestris, Micropterus spp. (Lake Erie), Lepomis gibbosus, Morone americana; Massachusetts



Lernaea cyprinacea is a parasitic copepod, in which the adult female, after fertilization, becomes a worm-like parasite, permanently attached to a fish or amphibian host. The transformed female produces many batches of attached, paired egg sacs, which hatch into non-feeding nauplius larvae. After three nauplius stages, the animal molts into the copepodite I stage. This stage, and successive stages II-V attach temporarily to fish hosts and feed from them. However, they are capable of swimming and moving from one host to another. Copepodite V molts into a free-swimming cyclopoid (adult) stage. Females attach to the surface of a host (not clear if this happens before or after mating), and mating occurs. The fertilized female then undergoes its transformation, penetrating the skin of a host and anchoring in the muscle tissue (Grabda 1963; Kabata 1979; Wilson 1918).

Lernaea cyprinacea is an ectoparasite with an extraordinary range of hosts, primarily fishes (more than 100 species), but also frogs (Bullfrogs- Lithobates catesbiana, Rana pipiens, Rana clamitans) and other species (Hofmann 1968; Shields and Tidd 1968; Kabata 1978). We have no records of this parasite from brackish waters. It has infected the euryhaline fish Fundulus heteroclitus (Mummichog) under experimental conditions, and tolerated salinities up to 12 PSU, but eggs did not develop at salinities above 3 .5 PSU (Shields and Sperber 1974). 


Fishes (many species); Frogs (Rana sp.)

Trophic Status:




General HabitatFresh (nontidal) MarshNone
General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
General HabitatNontidal FreshwaterNone
General HabitatTidal Fresh MarshNone
General HabitatUnstructured BottomNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Tidal RangeSubtidalNone
Vertical HabitatNektonicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)0Based on geographic range
Maximum Temperature (ºC)36Highest temperature tested (Shields and Tidd 1968).
Minimum Salinity (‰)0A freshwater species.
Maximum Salinity (‰)13For adult parasites attached to the euryhaline fish Fundulus heteroclitus (Mummichog) (Shields and Sperber (1979).
Minimum Reproductive Temperature20Experimental (Shields and Tidd 1968
Maximum Reproductive Temperature36Highest temperature tested (Shields and Tidd 1968).
Minimum Reproductive Salinity0A freshwater species.
Maximum Reproductive Salinity3.5For adult parasites attached to the euryhaline fish Fundulus heteroclitus (Mummichog) (Shields and Sperber (1979).
Broad Temperature RangeNoneCold temperate-Tropical
Broad Salinity RangeNoneNontidal Limnetic-Tidal Limnetic

General Impacts

Economic Impacts

Fisheries: Lernaea cyprinacea is now distributed throughout the temperate and tropical regions of the world, and is known from 100+species of fishes (Hoffman 1967; Hoffman and Schubert 1984; Kabata 1979). In cultured fish populations, it can be devastating, causing extensive mortality of fishes such as goldfish and carp, as well as unsightly lesions (Khalifa and Post 1976; Tidd 1934). High densities of fish in rearing ponds are likely to greatly favor this and other parasites (Wilson 1918).

While the occurrence of L. cyprinacea in wild fish populations has been frequently studied, its effects on population density, biomass, and structure are poorly known (Eisen 1983). Consequently, its effects on fisheries cannot be quantified. However, high rates of parasitism by L. cyprinacea are likely to detract from the perceived food and sporting qualities of freshwater fish.

Ecological Impacts

Parasitism: The occurrence, seasonal abundance, and host preference of Lernaea cyprinacea has been widely studied throughout its range (e.g. Adams 1984; Deutsch 1977; Deutsch 1978; Deutsch 1989; Haley and Winn 1959; Marcogliese 1991; Timmons and Hemstreet 1980). Although L. cyprinacea shows some preference for cyprinids and related families (e.g. Haley and Winn 1959), it is known to feed on more than 100 fish species, as well as the tadpoles of frogs and salamanders (Hoffman 1967; Kabata 1979; Tidd and Shields 1963). Infection of tadpoles with L. cyprinacea have been seen in the field as well as in the laboratory.

In experiments, copepodites of Lernaea cyprinacea favored the fins of Carassius auratus and the mouth and branchial chamber of tadpoles of Rana clamitans and Rana pipiens (Shields and Tidd 1974). However, in field surveys, gill infestations by copepodites are common (e.g., Deutsch 1978; Haley and Winn 1959). Heavy infestations of L. cyprinacea copepodites on the fins can result in fatal inflammation (Shields and Tidd 1974). Heavy infections of copepodites are especially damaging to the gill tissues, causing irritation and necrosis, and can kill the fish through lack of oxygen (Khalifa and Post 1976).

Adult L. cyprinacea can attack any part of the body surface of a fish, but the fins and gills are the most frequent sites of attachment (Deutsch 1978; Haley and Winn 1959; Timmons and Hemstreet 1980). The attached transformed adult female penetrates the skin of fishes and becomes deeply embedded in the host tissue, causing lesions which become hemorrhagic and eventually, necrotic. Muscle bundles near the site of penetration are also destroyed; penetration of the cranium and the walls of the intestine can also occur. The host response includes inflammation and occasionally the development of tumor-like growths around the site of penetration. Secondary bacterial and fungal infections around the lesion are also common (Khalifa and Post 1976). In tadpoles, the anchor of the parasite can affect the kidneys, liver, and spinal cord, as well as the muscle. However, the skin does not show the inflammation and abnormal growth responses characteristic of L. cyprinacea infestation in fishes (Tidd and Shields 1963). Parasitism by L. cyprinacea frequently causes mortality in fishes and tadpoles, particularly in smaller individuals. This may vary with the site of penetration, among other factors (Khalifa and Post 1976). However, parasitized fish are capable of rejecting adult parasites, even after host penetration. The host's ability to do this is highly variable, and may depend on immunological history and overall health (Shields and Goode 1978).

While L. cyprinacea has been extensively studied in terms of prevalence and pathology, and it is known as a serious pest in aquaculture situations, its impact on the density, biomass, and age-structure of natural fish populations is not well understood. Parasitism by L. cyprinacea did not influence mortality due to predation in parasitized Pimephales promelas (Fathead Minnow) exposed to Walleye (Sander vitreus) and Northern Pike (Esox lucius) (Vaughan and Coble 1975). In many natural populations, while a high percentage of fish are infested, most have only one parasite. Eisen (1983) has modeled the mortality as a function of parasite prevalence, parasites per fish, and the proportion of a fish's surface which is 'critical', where penetration is likely to be lethal. He argues that the parasite population is regulated by the mortality of the host, but that parasite density does not regulate the host population (Eisen 1983). However, empirical studies of natural populations of the host and parasite have not been conducted.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
GL-II Lake Erie 1931 Def Estab
P090 San Francisco Bay 1973 Def Estab
P260 Columbia River 1948 Def Estab
S060 Winyah Bay 1978 Def Estab
S070 North/South Santee Rivers 1978 Def Estab
S080 Charleston Harbor 1978 Def Estab
S090 Stono/North Edisto Rivers 1978 Def Estab
S110 Broad River 1978 Def Estab
S100 St. Helena Sound 1978 Def Estab
S120 Savannah River 1978 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
31778 OSPR - Historic Data 1973 9999-01-01 Fish screen facility, Tracy Def 37.7965 -121.5849


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