Cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...

and related species in the family Gadidae are susceptible to a variety of diseases and parasites.

''Laenaeocera branchialis''

Lernaeocera branchialis ''Lernaeocera branchialis'', sometimes called cod worm, is a parasite of marine fish, found mainly in the North Atlantic. It is a marine copepod which starts life as a small pelagic crustacean larva. It is among the largest of copepods, ranging ...

'', the "cod worm", is a

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

that infects gadoids. The first host used by cod worm is a

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish order (biology), order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the ...

lumpsucker The Cyclopteridae are a family of marine fishes, commonly known as lumpsuckers or lumpfish, in the order Scorpaeniformes. They are found in the cold waters of the Arctic, North Atlantic, and North Pacific oceans. The greatest number of species ar ...

, which it captures with grasping hooks at the front of its body. It penetrates the lumpsucker with a thin

filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * Solar filament ...

, which it uses to suck the host's blood. The nourished cod worm then mates with another one on the lumpsucker.Matthews B (1998
''An Introduction to Parasitology''
Page 73–74. Cambridge University Press. . The female worm, with her now-fertilized eggs, then finds a cod, or a cod-like fish, such as a

haddock The haddock (''Melanogrammus aeglefinus'') is a saltwater ray-finned fish from the family Gadidae, the true cods. It is the only species in the monotypic genus ''Melanogrammus''. It is found in the North Atlantic Ocean and associated seas where ...

or whiting. There, the worm clings to the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s while it metamorphoses into a plump, sinusoidal, worm-like body, with a coiled mass of egg strings at the rear. The front part of the worm's body penetrates the body of the cod until it enters the rear bulb of the host's

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

. There, firmly rooted in the cod's circulatory system, the front part of the parasite develops like the branches of a tree, reaching into the main

artery An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...

. In this way, the worm extracts nutrients from the cod's blood, remaining safely tucked beneath the cod's gill cover until it releases a new generation of offspring into the water.

Parasites of Atlantic cod

Nematoda Gadus Morhua Fish MArket Atlantic Canada

Atlantic cod act as intermediate, paratenic, or definitive hosts to a large number of parasite species; 107 taxa are listed by Hemmingsen and MacKenzie (2001)Perdiguero-Alonso D., Montero F. E., Raga J. A. & Kostadinova A. (2008). "Composition and structure of the parasite faunas of cod, ''Gadus morhua'' L. (Teleostei: Gadidae), in the North East Atlantic". ''

Parasites & Vectors ''Parasites & Vectors'' is a peer-reviewed open-access medical journal published by BioMed Central. The journal publishes articles on the biology of parasites, parasitic diseases, intermediate hosts, vectors and vector-borne pathogens. ''Parasites ...

'' 1: 23. with seven new records by Perdiguero-Alonso ''et al.'' (2008). The predominant groups of cod parasites in the northeast Atlantic were trematodes (19 species) and nematodes (13 species), including larval anisakids, which comprised 58.2% of the total number of individuals. Parasites of Atlantic cod include copepods, digeneans, monogeneans, acanthocephalans, cestodes, nematodes, myxozoans and protozoans:

Monogenea Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reprod ...

* ''

Diclidophora merlangi ''Diclidophora'' is a genus of flatworms belonging to the family Diclidophoridae. The genus has almost cosmopolitan distribution. Species: *'' Diclidophora caudospina'' *'' Diclidophora denticulata'' *'' Diclidophora embiotocae'' *'' Diclid ...

Trematoda Trematoda is a Class (biology), class of flatworms known as flukes. They are obligate parasite, obligate internal Parasitism, parasites with a complex biological life cycle, life cycle requiring at least two Host_(biology), hosts. The intermedia ...

– metacercariae * Bucephalinae gen. sp. * '' Cryptocotyle lingua'' * '' Otodistomum'' sp. * '' Prosorynchoides gracilescens'' * '' Prosorhynchus crucibulum'' * ''

Rhipidocotyle Bucephalidae is a family of trematodes that parasitize fish. They lack suckers, having instead a muscular organ called a "rhynchus" at the front end which they use to attach to their hosts. The characteristics of the rhynchus are used to help def ...

'' sp. Trematoda – adult * '' Derogenes varicus'' * '' Fellodistomum'' sp. * '' Gonocerca phycidis'' * '' Hemiurus communis'' * '' Hemiurus levinseni'' * '' Hemiurus luehei'' * '' Lecithaster'' sp. ?''gibbosus'' * '' Lepidapedon elongatum'' * '' Lepidapedon rachion'' * '' Opechona bacillaris'' * '' Podocotyle reflexa'' * '' Stephanostomum'' spp. * '' Steringotrema'' sp.

Cestoda Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of man ...

– larval forms * '' Grillotia'' sp. * '' Hepatoxylon'' sp. * '' Lacistorhynchus'' sp. * '' Scolex pleuronectis'' * Pseudophyllidea fam. gen. sp. * '' Schistocephalus gasterostei'' *

Trypanorhyncha ''Trypanorhyncha'' is an order of cestodes, a type of flatworm. Some species infect gamefish, such as sciaenids, during the parasitic worm's plerocercoid stage, and are commonly called spaghetti worm because of their appearance, approximating ...

fam. gen. sp. * Unidentified plerocercoids

– adult * '' Abothrium gadi'' Nematoda – larval forms * ''

Anisakis simplex ''Anisakis simplex'', known as the herring worm, is a species of nematode in the genus ''Anisakis''. Like other nematodes, it infects and settles in the organs of marine animals, such as salmon, Mackerel, mackerels and Squid, squids. It is commo ...

'' (s.l.) * ''

Contracaecum osculatum ''Contracaecum'' is genus of parasitic nematodes from the family Anisakidae. These nematodes are parasites of warm-blooded, fish eating animals, i.e. mammals and birds, as sexually mature adults. The eggs and the successive stages of their larvae ...

'' (s.l.) * ''

Hysterothylacium aduncum ''Hysterothylacium'' is a genus of parasitic roundworms in the family Raphidascarididae. As of 2020 it consists of over 70 species and is considered one of the largest of the ascaridoid genera parasitising fish. Ecology Species in the genus com ...

'' * '' Hysterothylacium rigidum'' * ''

Pseudoterranova decipiens ''Pseudoterranova'' is a genus within the family Anisakidae of parasitic nematodes with an aquatic life cycle. The lifecycle of ''Pseudoterranova'' spp. involves marine mammals, pinnipeds (sea lions, seals and walruses) as definitive hosts, plank ...

'' (s.l.) * '' Rhapidascaris'' sp. Nematoda – adults * '' Ascarophis morrhuae'' * '' Ascarophis crassicollis'' * '' Ascarophis filiformis'' * '' Capillaria gracilis'' * '' Cucullanus cirratus'' * ''

Cucullanus ''Cucullanus'' is a genus of parasitic nematodes.Shamsi, S. (2016). ''Cucullanus'' Müller, 1777. In: Guilini, K.; Bezerra, T.N.; Deprez, T.; Fonseca, G.; Holovachov, O.; Leduc, D.; Miljutin, D.; Moens, T.; Sharma, J.; Smol, N.; Tchesunov, A.; M ...

'' sp. * ''

'' * '' Spinitectus'' sp. Acanthocephala – post-cystacanths * ''

Corynosoma semerme ''Corynosoma'' is a genus of parasitic worms belonging to the family Polymorphidae. The genus has almost cosmopolitan distribution. Species: *''Corynosoma alaskensis'' *''Corynosoma australe'' *'' Corynosoma beaglense'' *'' Corynosoma bullo ...

'' * ''

Corynosoma strumosum ''Corynosoma'' is a genus of parasitic worms belonging to the family Polymorphidae. The genus has almost cosmopolitan distribution. Species: *''Corynosoma alaskensis'' *''Corynosoma australe'' *'' Corynosoma beaglense'' *'' Corynosoma bullo ...

'' Acanthocephala – adults * '' Echinorhynchus gadi'' (s.l.) Hirudinea – adults * '' Calliobdella nodulifera'' * '' Johanssonia arctica'' Copepoda - larval forms * ''

Caligus ''Caligus'' is a genus of sea lice in the family Caligidae. The species are parasites of marine fishes and could be vectors of viruses. , the World Register of Marine Species includes the following species: *'' Caligus absens'' Ho, Lin & Che ...

'' sp. copepodite * Copepoda fam. gen. sp. copepodite Copepoda – adults * '' Acanthochondria soleae'' * ''

Caligus curtus ''Caligus curtus'' is a sea louse species. It is a parasite of the Atlantic cod. References

Siphonostomatoida Crustaceans of the Atlantic Ocean Parasitic crustaceans Animal parasites of fish Crustaceans described in 1785 Taxa named by Ot ...

'' * '' Caligus diaphanus'' * ''

Caligus elongatus ''Caligus'' is a genus of sea lice in the family Caligidae. The species are parasites of marine fishes and could be vectors of viruses. , the World Register of Marine Species includes the following species: *'' Caligus absens'' Ho, Lin & Che ...

'' * '' Chondracanthus ornatus'' * '' Clavella adunca'' * '' Holobomolochus confusus'' * ''

Amphipoda Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far desc ...

* '' Lafystius sturionis''

Isopoda Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

* '' Gnathia elongata'' (praniza larva)

References

This article incorporates CC-BY-2.0 text from the reference: Perdiguero-Alonso D., Montero F. E., Raga J. A. & Kostadinova A. (2008). "Composition and structure of the parasite faunas of cod, ''Gadus morhua'' L. (Teleostei: Gadidae), in the North East Atlantic". ''

'' 2008, 1: 23. doi:10.1186/1756-3305-1-23

''Laenaeocera branchialis''

Parasites of Atlantic cod

References

Further reading