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Phylum Nematoda
Common name: round worms
>20,000 species. Mostly widespread and
abundant of all metazoans 90,000 worms in a
decomposing apple. Marine and freshwater
benthos, soil, parasites on plants and animals
hooge.developmentalbiology.com/meiofauna/media
Phylum Nematoda - Anatomy
Most freeliving <2.5 mm in length. Some parasites > 50 cm in length.
Body is cylindrical with a pseudocoel
/creatures.ifas.ufl.edu/nematode
Nerve cords
Ovaries Excretory canal
Digestive tract
Complex cuticle Must molt (Ecdysis)
Anterior end is radially symmetrical but the rest of the body has bilateral symmetry
/creatures.ifas.ufl.edu/nematode
Phylum Nematoda - Head RegionNervous system
/creatures.ifas.ufl.edu/nematode
Brain
Ring-like brain
Sensilla Chemosensory Males also have them
near the anus
Sensilla
www.unice.fr/LEML/coursJDV/images/biologie/
Sensilla
www.unice.fr/LEML/coursJDV/images/biologie/
Dorsal, ventral and lateral nerve cords
/creatures.ifas.ufl.edu/nematode
Phylum Nematoda - Head Region
3-6 lips at the mouth3 to 6 lips
Buccal Cavity
Stylet - like aHypodermic needle
Buccal Cavity varies depending on prey Bacteria - no teeth or
stylet Plant root - stylet Carnivore - small teeth
and sometimes stylet Intestine - large hook-
like teeth
Muscular pharynx
Pharynx
/creatures.ifas.ufl.edu/nematode
Phylum Nematoda - Digestive tract/creatures.ifas.ufl.edu/nematode
Foregut (buccal cavity and pharynx shown earlier)
/creatures.ifas.ufl.edu/nematode
Midgut -Intestine
Intestine
Cuticle
/creatures.ifas.ufl.edu/nematode
Hindgut - RectumRectum
Anus
Phylum Nematoda – Excretion
Excretory glands and canals thought to be involved in: Osmoregulation Ionic regulation Excretion of waste metabolites
Ammonia secreted through body wall
Nerve cords
Ovaries Excretory canal
Digestive tract
www.ustboniface.mb.ca/cusb/abernier/Animaux/Pseudocoelom
LongitudinalMuscles
Phylum Nematoda – Musculature
Longitudinal muscles only!
Nerve cords
Ovaries Excretory canal
Digestive tract
www.ustboniface.mb.ca/cusb/abernier/Animaux/Pseudocoelom
LongitudinalMuscles
Phylum Nematoda - Reproduction
Separate sexes - usually Males have hook-like posterior
Testis Male Rectum - Cloaca
Reproduction Digestive waste
Spicule for sperm transfer Retractable
www.apsnet.org/education/LessonsPlantPath/PineWilt/images/
creatures.ifas.ufl.edu/nematode/
Spicule Testis
Rectum - Cloaca
Phylum Nematoda - Reproduction
Females Ovaries Eggs Vulva Seminal Receptacle
creatures.ifas.ufl.edu/nematode/
creatures.ifas.ufl.edu/nematode/
Ovary
Eggs
Seminal recepticle
Vulva
Phylum Nematoda - Parasites: Roundworm Life Cycles
www.extension.umn.edu/distribution/cropsystems/images
Plant parasite
Racoon parasite
Baylisacaris procyonis
Human ParasiteAscaris lumbricoides