Topic 10 Nematomorpha
Download
Report
Transcript Topic 10 Nematomorpha
Nematomorpha
Also known as:
-Gordian Worms
-Horsehair Worms
Biodiversity Institute of Ontario
Onychophora
Tardigrada
Arthropoda
Ecdysozoa
Nematoda
Nematomorpha
Priapulida
Loricifera
Kinorhyncha
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.
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.
Life Cycle
Have both a parasitic stage, and free-living stage
Four life stages:
Egg
Pre-parasitic larva
Parasitic larva
Free-living adult
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).
Adult
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.
Adults
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..
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
Common Life Cycle
http://www.nematomorpha.net/Nematomorphs.html
Distribution
They are found worldwide and there are about 325
described species, although many more undescribed
species undoubtedly exist.