Life Cycle of Copepods
Copepods are a group of waterborne crustaceans that can be found is every ocean, sea and freshwater habitat. They can live both as planktonic (free swimming) or benthic (on the floor) while some live an amphibious lifestyle. Large concentrations of these parasites can be found in underwater caves and sinkholes. Some copepods are parasitic in nature, while others are do not depend on host organisms to survive. Copepods have been identified as being one of the most important organisms in the carbon cycle.
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History and Significance
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Copepods are important contributions to the environment. Due to their large numbers, they make up a significant portion of the zooplankton that many aquatic species of fish and other life eat. Many scientists speculate that they are the most populous animal species on the planet. There are subspecies of copepods that live as internal parasites, others as external parasites and can attach themselves to a wide number of hosts including: sharks, fish, mollusks, whales and dolphins. Some can even invade humans.
Reproduction
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Reproduction occurs sexually in copepods. The eggs may be laid directly into the water or held in a specialized sac within the female until hatching occurs. If the eggs are laid directly into the water, they are enclosed in a tough shell which will protect them for an extended period of time, even if the pond dries out.
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Early Development
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The eggs hatch into a larvae which will feed, grow and molt several times before becoming a copepdid larva. This is the teenage stage of the life cycle. The copepdid larva closely resembles an adult, though certain characteristics have not developed, such as a segmented body or the development of the remaining pairs of legs.
Maturation
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After three more molts, the copepod is considered an adult and capable of reproducing. This process can take from seven days up to a year to complete, based on the species.
Human Infection
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A specific invasive worm known as Dracunculus medinensis, or guinea worm is known to cause Dracunculiasis, or guinea worm disease in humans. Copepods will ingest the larvae of the guinea worm, becoming the intermidiary host. Humans become infected by drinking untreated water that contains the infected copepods. After ingestion, the adult copepods will die and release the larvae that have been living inside the crustacean. The larvae penetrate the lining of the stomach of the new primary host and take up residence inside the abdominal cavity. After maturation, the female guinea worm will release a chemical that causes a large blister to form on the skin. When the skin comes into contact with water, the female worm will emerge and release the newly hatched larvae into the water. These larvae are ingested by adult copepods where they will develop into infective larvae and then wait to be consumed again to start the process over again.
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