Belongs within: Podoplea.
The Lernaeidae are long-bodied freshwater copepods that are ecto- or mesoparasites of fish.
Anchor worm
Published 27 February 2023
Parasitic lifestyles have evolved in copepods on a number of occasions. Often, these parasites are highly modified, requiring close inspection to even be recognized as copepods. Take, for instance, the anchor worms of the Lernaeidae.
The Lernaeidae are a family of cyclopoid copepods found in fresh water where most of them are parasites of fish. Only the adult females are parasitic; juveniles and males are free-living, and look much more like ordinary copepods than the females. In the best known species, Lernaea cyprinacea, the males and females mate on the host fish during the fourth copepodid stage of the life cycle. After copulation, the males presumably die while the females attach to their host, transform into adults and begin egg production (Plaul et al. 2010). Gills look to be a common target of attachment though at least some species may also attach elsewhere on the body.
Ho et al. (1998) divided the lernaeids between two subfamilies, the Lernaeinae and Lamprogleninae. The adult females of both subfamilies are long-bodied. Members of the Lamprogleninae and the genus Pillainus of the Lernaeinae are ectoparasites, clinging to their host with large maxillae. The remaining Lernaeinae are mesoparasites with the cephalothorax transformed into a radiating holdfast embedded in the host tissue; these are the forms commonly referred to as ‘anchor worms’. In most genera, the segments of the metasoma are fused into a neck and trunk, though they remain indistinctly separated in the genera Lamproglena and Pseudolamproglena. Eggs are produced in a uniseriate sac in the Lamprogleninae but the egg sac is multiseriate in most Lernaeinae (again, excepting Pillainus).
About 110 species of Lernaeidae have been described to date with the highest diversity in Africa and southern Asia (Ho et al. 1998), though it may be questioned how much this reflects a bias in study. Some have become notable pests from a human perspective. Lamproglena monodi, a parasite of the gills of cichlids such as tilapia, has spread from its native home in Africa to South America in association with its hosts (Azevedo et al. 2012). The anchor worm Lernaea cyprinacea is similarly a native of Eurasia and Africa that is now almost cosmopolitan. Though originally described from carp, L. cyprinacea is very much a generalist, known from a wide range of host fishes as well as amphibians. It has even been recorded on freshwater insects, albeit with some question as to whether it was actively drawing nutrients from them (McAllister et al. 2011). Infestations of L. cyprinacea can have a significant impact on their hosts, causing (among other things) ulceration, blood loss, emaciation and potentially death (Plaul et al. 2010). These effects can add up to a significant economic loss for affected fish industries. Infestation with L. cyprinacea is strongly correlated with warm temperatures; as water temperatures rise due to climate change, the area affected reaches higher latitudes.
Systematics of Lernaeidae
<==Lernaeidae |--Lernaea Linnaeus 1758L58 | |--L. argentinensisPRB10 | |--L. asellina Linnaeus 1758L58 | |--L. branchialisG20 | |--L. cyprinacea Linnaeus 1758L58 | `--L. salmonea Linnaeus 1758L58 |--Lamproglena von Nordmann 1832II00 | |--L. angustaII00 | |--L. barbicolaII00 | |--L. cleopatra Humes 1957II00 | |--L. hemprichii von Nordmann 1832II00 | |--L. monodi Capart 1944II00 | |--L. nyasae Fryer 1961II00 | `--L. werneriII00 |--Areotrachelus truchaePRB10 `--TaurocherosPRB10 |--T. salminisiiPRB10 `--T. tarangophilusPRB10
*Type species of generic name indicated
References
Azevedo, R. K. de, V. D. Abdallah, R. J. da Silva, T. M. P. de Azevedo, M. L. Martins & J. L. Luque. 2012. Expanded description of Lamproglena monodi (Copepoda: Lernaeidae), parasitizing native and introduced fishes in Brazil. Rev. Bras. Parasitol. Vet., Jaboticabal 21 (3): 263–269.
[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.
Ho, J.-S. 1998. Cladistics of the Lernaeidae (Cyclopoida), a major family of freshwater fish parasites. Journal of Marine Systems 15: 177–183.
[II00] Ibraheem, M. H., & K. Izawa. 2000. On the morphology of Lamproglena monodi Capart, a parasitic copepod on the gills of tilapia in Egypt. Zoology in the Middle East 21: 103–108.
[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.
McAllister, C. T., C. R. Bursey & S. D. Martin. 2011. Lernaea cyprinacea (Crustacea: Copepoda: Lernaeidae) anchorworms from two larval aquatic insects (Ephemeroptera: Baetidae, Trichoptera: Hydropsychidae) in northeastern Oklahoma. Proc. Okla. Acad. Sci. 91: 37–40.
[PRB10] Plaul, S. E., N. G. Romero & C. G. Barbeito. 2010. Distribution of the exotic parasite, Lernaea cyprinacea (Copepoda, Lernaeidae) in Argentina. Bulletin of the European Association of Fish Pathologists 30 (2): 65–73.