Nematomorpha

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Nematomorpha
Also known as -Gordian Worms -Horsehair Worms
Biodiversity Institute of Ontario
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Onychophora
Tardigrada
Arthropoda
Nematoda
Ecdysozoa
Nematomorpha
Priapulida
Loricifera
Kinorhyncha
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Morphology

• Extremely long and thin worms. They are only 1-2
  mm in diameter, but up to 3 feet long
• Known as the horsehair or gordian worms.
• Non-segmented with an indistinct head no wider
  than the body.
• Found predominantly in freshwater (with a few
  marine exceptions). Adults are free-living but
  larvae are parasitic.

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Biological Systems

• They are pseudocoelomates and have no specialized
  circulatory or respiratory system and also lack
  excretory organs
• Have a digestive system that has atrophied and
  they absorb soluble nutrients across their body
  wall.

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Life Cycle

• Have both a parasitic stage, and free-living
  stage
• Four life stages
• Egg
• Pre-parasitic larva
• Parasitic larva
• Free-living adult

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Larva

• Egg laid in water hatches in 15-80 days producing
  a swimming larva with an eversible barbed
  probosicis.
• Larva enters the body cavity of an arthropod host
  where it lives for about a year, grows, and
  undergoes metamorphosis (many species have two
  hosts).

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Adult

• Once larva has almost reached adult stage, it
  begins manipulating the hosts behavior.
• When ready to emerge, the adults manipulate the
  host into entering water. The mechanism is
  unknown.
• The adult bursts from the body cavity of the
  host, killing it in the process.

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Adults

• Once the adults emerge, they stop feeding and all
  of the worms energy is directed towards
  reproduction.
• Nematomorphs reproduce sexually and a female
  nematomorph may deposit one million eggs in
  water..

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Different Life Cycles

• Larva ? Intermediate host ? Definitive Host
• Most common
• Larva ? Plant matter ? Definitive Host
• Often found in species that live in temporary
  ponds.
• Larva ? Definitive Host
• Least common

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Common Life Cycle
http//www.nematomorpha.net/Nematomorphs.html
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Distribution

• They are found worldwide and there are about 325
  described species, although many more undescribed
  species undoubtedly exist.