Overview

Distribution

southern Gaspe waters (Baie des Chaleurs, Gaspe Bay to American, Orphan and Bradelle banks; eastern boundary: eastern Bradelle Valley), Magdalen Islands (from Eastern Bradelle valley to the west, as far as Cape North, including the Cape Breton Channel), Prince Edward Island (from the northern tip of Miscou Island, N.B. to Cape Breton Island south of Cheticamp, including the Northumberland Strait and Georges Bay to the Canso Strait causeway), upper North Shore (between Sept- Iles and Pointe des Monts), middle North Shore (from Sept - Iles to Cape Whittle, including the Mingan Island), Lower North Shore, Laurentian Channel (bathyal zone) to the Northeast of Anticosti Island (=Jacques Cartier Strait), Laurentian Channel (bathyal zone)(=Esquiman Channel), lower Laurentian Channel (bathyal zone as far as Cabot Strait: Cape North, N.S., St. Paul Island to Cape Ray, NL.), western slope of Newfoundland, including the southern part of the Strait of Belle Isle but excluding the upper 50m in the area southwest of Newfoundland, and including the Southwest slope of NL
  • North-West Atlantic Ocean species (NWARMS)
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Geographic Range

Lernaeocera branchialis is an ectoparasitic crustacean of cod and haddock found mainly in the North Atlantic.

Biogeographic Regions: atlantic ocean (Native )

  • Jones, J. 1998. Distant water sailors: parasitic copepoda of the open ocean. J. Marine Systems, 15: 207-214.
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Physical Description

Morphology

Physical Description

Lernaeocera branchialis is among the largest of copepods. It ranges in size from 2-3 mm as a chalimus (a specialized copepodid larva) to more than 40 mm as an adult. Lernaeocera branchialis is highly evolved as an adult, having lost all semblance of crustacean heritage, and is therefore identified by its larval stages. As an adult, it appears S-shaped with 2 pairs of antennae on its head. This ectoparasite also has 2 pairs of maxillae used for piercing gill flesh, 1 pair of mandibles, and reduced antennules. Although the division between its head and trunk is not clearly defined, its posterior body segmentation in its larval stages is distinguishably crustacean. As a female adult, it appears as a mass of egg strings with a large egg sac. On a host, these parts of L. branchialis are seen external to the fish's body, and its egg sac is connected to other parts that lie internal to the fish host. These parts consist of a complex of antlers used for piercing, sucking, and maintaining feeding position. Respiration in L. branchialis is achieved through gills, and sometimes through its body surface.

Range length: 40 (high) mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

  • Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology. 6th Ed.. USA: McGraw-Hill Companies, Inc..
  • Scholz, T. 2001. Parasites in cultured and feral fish. Veterinary Parasitology, 84: 317-335.
  • Schram, T., P. Heuch. 2001. The egg string attachment mechanism of selected pennellid copepods. J. Mar. Biol. Ass. U. K., 81: 23-32.
  • Van Damme, P. 1995. . Morphological and morphometric study on crustacean parasites with the genus Lernaeocera . International J. for Parasitology, 25: 1401-1411.
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Ecology

Habitat

ectoparasite found as larvae on Cyclopterus lumpus and Gadus morhua; bathyal and circalittoral of the Gulf and estuary
  • North-West Atlantic Ocean species (NWARMS)
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Lernaeocera branchialis is strictly aquatic, being pelagic and in the upper 200 m of open ocean.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: pelagic

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Trophic Strategy

Food Habits

Lernaeocera branchialis parasitizes cod and haddock. It feeds on blood though root-like attachment organs, which invade throughout host tissue. Like other species of the Pennellidae family, it has a characteristic anterior site of growth and feeding. Lernaeocera branchialis attaches to the host fish in the branchial area. The parasite's cephalothorax grows into and through the ventral aorta, which is accomplished with its grotesque antler complex. The parasite inserts its antlers into the host's fleshy gill cavity by 3 branched processes, aided by strong antennae and maxillae for piercing into the wall of the bulbus arteriosus.

Animal Foods: body fluids

Primary Diet: carnivore (Eats body fluids)

  • Matthews, B. 1998. An Introduction to Parasitology. Cambridge: University Press.
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Associations

Ecosystem Roles

Lernaeocera branchialis parasitizes cod and haddock.

Ecosystem Impact: parasite

Species Used as Host:

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Predation

Larval mortality is high as few individuals make it to the suitable host. This species may be preyed on by fish.

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Life History and Behavior

Behavior

Communication and Perception

Crustaceans have various sensory resceptors, mainly setae over the body. Photoreceptors are also generally present.

Communication Channels: tactile ; chemical

Perception Channels: tactile ; chemical

  • Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusets: Sinauer Associates, Inc..
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Life Cycle

Development

The development of L. branchialis consists of several stages, begining when the animal hatches from an egg as a non-parasitic, free-swimming nauplius (the early larval stage of crustaceans). Three pairs of appendages (antennules, antennae, and mandibles) are used mainly for locomotion. Lernaeocera branchialis develops into a copepodid, which attaches to an intermediate host, such as a lumpfish (e.g. Cyclopterus lumpus), sculpin (Cottidae), or flounder (Pleuronectidae). After development into a chalimus, it copulates with another chalimus of the opposite sex and detaches. Lernaeocera branchialis is only 2 to 3 mm long at this point and is still resembles a copepod. It then undergoes a pelagic stage and searches for a definitive host. Once attached to the gill area of a cod or haddock, it undergoes profound metamorphosis and develops an egg sac and antlers. Any recognizable external segmentation is lost, and it grows more than 40 mm, excluding egg strings. In its final stages, L. branchialis appears reddish and worm-like, with its head (connected by a neck to a soft body) buried in gills. As a feeding adult, it is reduced to body parts needed for reproduction, feeding, and holding its position within the cod or haddock.

In comparison to other pennelids, its larval stage is almost indistinguishable from the larva of its free-living adult relatives. Although the biological role of L. branchialis larvae is unchanged, its adult form has adopted parasitism.

Development - Life Cycle: metamorphosis

  • Croll, N. 1966. Ecology of Parasites. Cambridge: Harvard University Press.
  • Lapage, G. 1951. Parasitic Animals. Cambridge: University Press.
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Reproduction

Lernaeocera branchialis develops into a copepodid, which attaches to an intermediate host, such as a lumpfish (e.g. Cyclopterus lumpus), sculpin (Cottidae), or flounder (Pleuronectidae). After development into a chalimus, it copulates with another chalimus of the opposite sex and detaches. Lernaeocera branchialis is only 2 to 3 mm long at this point and is still resembles a copepod. It then undergoes a pelagic stage and searches for a definitive host. Once attached to the gill area of a cod or haddock, it undergoes profound metamorphosis and develops an egg sac and antlers. Any recognizable external segmentation is lost, and it grows more than 40 mm, excluding egg strings.

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

Parental Investment: pre-fertilization (Provisioning)

  • Croll, N. 1966. Ecology of Parasites. Cambridge: Harvard University Press.
  • Lapage, G. 1951. Parasitic Animals. Cambridge: University Press.
  • Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology. 6th Ed.. USA: McGraw-Hill Companies, Inc..
  • Van Damme, P. 1995. . Morphological and morphometric study on crustacean parasites with the genus Lernaeocera . International J. for Parasitology, 25: 1401-1411.
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Conservation

Conservation Status

US Federal List: no special status

CITES: no special status

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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Lernaeocera branchialis causes severe damage by invasively feeding on blood. Death of the fish may occur from open lesions, too much blood loss, or possible formations of clots and occlusions of the aorta or blood vessels. Lernaeocera branchialis also causes a 20-30% loss of weight and liver fat in fish from the effects of growth retardation. It also has profound effects on reproduction by delaying gonad development and sexual maturity, and its presence influences fish behavior and reduces its resistance to other stresses. Lernaeocera branchialis is also known to be one of the most serious agents of trypanosomal parasites in Gadus mordua (cod). Overall, the parasite's changes on fish body weight loss and increased mortality affects commercial fisheries by making it more expensive to market cod, haddock, and flounder.

  • Rohde, K. 1993. Ecology of Marine Parasites: An Introduction to Marine Parasitology. 2nd Ed.. Trowbridge (UK): Redwood Books.
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Wikipedia

Lernaeocera branchialis

Lernaeocera branchialis, sometimes called cod worm, is a parasite of marine fish, found mainly in the North Atlantic.[2] It is a marine copepod which starts life as a small pelagic crustacean larvae. It is among the largest of copepods, ranging in size from 2–3 millimetres when it matures as a copepodid larva to more than 40 millimetres (1.6 in) as an adult.

Lernaeocera branchialis is ectoparasitic, which means it is a parasite that lives primarily on the surface of its hosts. It has many life stages, some of which are motile and some of which are sessile. It goes through two parasitic stages, one where it parasites as a secondary host a flounder or lumpsucker, and another stage where it parasites as a primary host a cod or other fishes of the cod family (gadoids). It is a pathogen that negatively impacts the commercial fishing and mariculture of cod-like fish.

Life stages[edit]

The life-cycle of a cod worm involves a complex progression of life stages, including two successive hosts. It comprises "two free-swimming nauplius stages, one infective copepodid stage, four chalimus stages and the adult copepod, each separated by a moult".[3]

The cycle begins with the females laying eggs which hatch into a nauplius, the usual early larval stage of crustaceans.[4] This nauplius moults about 10 minutes after hatching to produce nauplius II, and 48 hours later, nauplius II moults to a copepodid stage. At this point the copepodid is pelagic and free-swimming with an average length of about 0.5 mm.[3]

The next stage is finding a secondary or intermediate host, a demersal fish like a flounder or lumpfish which is often stationary and therefore easy to catch. The copepodid have only a day to find such a fish and attach themselves to its gills.[4]

When they locate such a fish, they capture it with grasping hooks at the front of their body. They penetrate the fish with a thin filament which they use to suck its blood. The nourished cod worms then progress via four moults from the naupliar stage to the mature chalimus stage. At this point the males transfer sperm to the females. Both sexes develop swimming setae, detach from the flounder or lumpfish and again swim freely as pelagic organisms.[4][5]

The female worm still resembles a copepod and is 2 to 3 mm long. She now undergoes another pelagic quest, searching this time for a definitive or primary host. With her fertilised eggs, she looks for a cod or a fish belonging to the same family as cod, such as a haddock or whiting.[4]

When she locates one the worm enters the gill chamber. There she clings to the gills and metamorphoses into a plump, sinusoidal, wormlike body, with a coiled mass of egg strings at her rear.[4] These bodies are mostly about 20 mm long, but can measure up to 50 mm.[6] 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. There, firmly rooted in the cod's circulatory system, the front part of the parasite develops in the shape of antlers or branches on a tree, reaching into the main artery. In this way, while safely tucked beneath the cod's gill cover, the worm feeds from one end on cod blood while it pumps new offspring out the other end.[4][5]

Behaviour[edit]

It is not known how L. branchialis searches for its fish hosts, but it probably uses chemoreceptors and mechanoreceptors, and follows physical clues in the water column such as those provided by haloclines and thermoclines.[3]

Effects on fisheries[edit]

The most serious parasitic crustaceans among fish in general are sea lice.[7] However, L. branchialis is probably the most serious parasitic crustacean among cod. Infestation reduces the efficiency with which food can be utilised, delaying the development of the gonads. Up to 30% loss in weight can occur, with increases in mortality because of open lesions with loss of blood, and possibly occlusion of vessels or aorta.[7] These can have commercial impacts on wild fisheries, making cod-like fishes more expensive to market.[7][8] Gadoids, particularly cod, are emerging marine aquaculture species in some North Atlantic countries. L. branchialis present potential problems for their successful mariculture.[9]

References[edit]

  1. ^ Geoff Boxshall (2011). "Lernaeocera branchialis (Linnaeus, 1767)". In T. Chad Walter & Geoff Boxshall. World Copepoda database. World Register of Marine Species. Retrieved March 11, 2011. 
  2. ^ J. B. Jones (1998). "Distant water sailors: parasitic Copepoda of the open ocean". Journal of Marine Systems 15: 207–214. doi:10.1016/S0924-7963(97)00056-0. 
  3. ^ a b c Adam Jonathan Brooker (2007). Aspects of the biology and behaviour of Lernaeocera branchialis (Linnaeus, 1767) (Copepoda : Pennellidae) (PDF) (PhD thesis). University of Stirling. 
  4. ^ a b c d e f Bernard E. Matthews (1998). "From host to host". An Introduction to Parasitology. Cambridge University Press. pp. 52–78. ISBN 978-0-521-57691-8. 
  5. ^ a b Ross Piper (2007). "Cod worm". Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Greenwood Press. pp. 180–182. ISBN 978-0-313-33922-6. 
  6. ^ Z. Kabata (1979). Parasitic Copepoda of British Fishes. London: Ray Society. ISBN 978-0-903874-05-2. 
  7. ^ a b c Tomáš Scholz (1999). "Parasites in cultured and feral fish" (PDF). Veterinary Parasitology 84 (3–4): 317–335. doi:10.1016/S0304-4017(99)00039-4. PMID 10456421. 
  8. ^ Klaus Rohde (1993). Ecology of Marine Parasites: An Introduction to Marine Parasitology (2nd ed.). CAB International. p. 198. ISBN 978-0-85198-845-0. 
  9. ^ Fisheries Research Services (2005) Final report of the Aquaculture Health Joint Working Group sub-group on disease risks and interactions between farmed salmonids and emerging marine aquaculture species Page 29. Scotland. ISBN 0-9546490-8-7

Further reading[edit]

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