Lernaeocera branchialisthroat-ogre

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Geographic Range

Lernaeocera branchialis is an ectoparasitic crustacean of cod and haddock found mainly in the North Atlantic. (Jones, 1998)

Habitat

Lernaeocera branchialis is strictly aquatic, being pelagic and in the upper 200 m of open ocean. (Jones, 1998)

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. (Roberts and Janovy Jr., 2000; Scholz, 2001; Schram and Heuch, 2001; Van Damme, 1995)

  • Range length
    40 (high) mm
    1.57 (high) in

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. (Croll, 1966; Lapage, 1951; Roberts and Janovy Jr., 2000; Van Damme, 1995)

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. (Croll, 1966; Lapage, 1951; Roberts and Janovy Jr., 2000; Van Damme, 1995)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Parental Investment
  • pre-fertilization
    • provisioning

Behavior

This species is a parasite which is motile or sessile, depending on its life stage.

Communication and Perception

Crustaceans have various sensory resceptors, mainly setae over the body. Photoreceptors are also generally present. (Brusca and Brusca, 2003)

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. (Matthews, 1998; Roberts and Janovy Jr., 2000)

  • Animal Foods
  • body fluids

Predation

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

Ecosystem Roles

Lernaeocera branchialis parasitizes cod and haddock.

Species Used as Host

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. (Lapage, 1951; Rohde, 1993; Scholz, 2001)

Conservation Status

Contributors

Renee Sherman Mulcrone (editor).

Aimee Austria (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

References

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

Croll, N. 1966. Ecology of Parasites. Cambridge: Harvard University Press.

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

Lapage, G. 1951. Parasitic Animals. Cambridge: University Press.

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

Roberts, L., J. Janovy Jr.. 2000. Foundations of Parasitology. 6th Ed.. USA: McGraw-Hill Companies, Inc..

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

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.