Biodiversity Institute of Ontario
Also known as:
-Gordian Worms
-Horsehair Worms

Ecdysozoa
Onychophora
Tardigrada
Arthropoda
Nematoda
Nematomorpha
Priapulida
Loricifera
Kinorhyncha

 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.

 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.

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

 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).

 Once larva has almost reached adult stage, it begins manipulating the host’s 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.

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

 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

http://www.nematomorpha.net/Nematomorphs.html

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