ZOO 115 Invertebrate Zoology

Nematoda

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

Phylum Nematoda - Parasites: Hookworm

www.biosci.ohio-state.edu/~parasite/lifecycles

Phylum Nematoda - Parasites: Trichinella

Phylum Nematoda - Parasites: Filariasis

www.cvm.okstate.edu/~users/jcfox/htdocs/DISK1/IMAGES/