Roundworms

Brittney Jackson, Kaylee Kraft, Jessica Lin

Basic Information

• Phylum Nematoda• Key roles in decomposition and nutrient recycling• Habitat:  soil, marine, freshwater sediment• More than 15,000 species• Most are free living • Parasites in animals and plants

Roundworm Bodies

• Microscopic bodies• Movements produced by contraction of longitudinal muscles• Elongated, cylindrical, threadlike body which is pointed at

both ends and covered by a tough, flexible cuticle• Cuticle gives nematode body shape and protection• Epidermis not composed of distinct cells•  Beneath epidermis is a layer of longitudinal muscles• No circular muscles present in the body wall• Fluid filled pseudocoelom (fluid filled cavity that contains

transports nutrients) that serves as a hydrostatic skeleton• Bilateral symmetry, complete digestive tract, complete

digestive tract, three definite tissue layers, and definite organ systems

Roundworm Bodies Continued

• Lack specific circulatory structures• Sexes are usually seperate• Male is smaller than the female• Absence of a well-defined head

Gas Exchange/ secretion

• no circulatory system• gas exchange and secretion by diffusion

Response to Stimuli

• Sensory Organso sensory hairs and papillae over the entire bodyo  Amphids- located on the head; small cavities; function as chemical

receptors• Nervous System

o 4 main nerves entire length of the body

o dorsal nerve controls muscle movement

o lateral nerves sensory information

o ventral nerve motor skills

• Braino  rings of the four primary nerveso motor responseso move to or away from stimuli

Movement

• thrash around• coil and uncoil • movement produced by the longitudinal muscles

Classification and Evolution

• Traditionally classified as a single phylum based on wormlike body strucutre

• Molecular evidence suggests roundworms evolved from complex animals by a simplification of their bodies

• Probably related to arthropods and can be classified as Ecdysozoa since like other arthropods/ecdysozoans they shed their cuticles periodically

Diseases• Ascariasis

o Symptoms: coughing, shortness of breath, weight loss, nausea, blood in stool, worms in stool

o Cause: contaminated food/water, Ascaris ( white worm)• Guinea worm disease

o Symptoms: start a year after infection when the worm is ready to lay eggs, which emerges through the skin producing a painful blister

o Cause: contaminated water• Loiasis

o Symptoms: itchy eyes, blurred vision, people see worms move across their eyes

o Cause:  Loa loa transmitted by day-biting flies•  Lymphatic filariasis

o  Symptoms: swelling/scarring of the legs/groino Cause: mosquito bites

• River blindnesso Symptoms: itchy rash, lose skin pigment, lose visiono Cause: spread by day-biting flies, leading cause of worldwide blindnes

Diseases Continued

• Trichinosiso Symptoms: diarrhea, high fever, muscle pain, sensitivity

to light, headache, and pink eyeo Cause: eating uncooked meat

• Threadwormo Symptoms: nausea, diarrhea, fever, coughing up blood, 

Ascariasis  Guinea worm disease  Lymphatic filariasis 

Ascaris

• 10 inches long• adult life in human intestine• separate sexes• female can produce up to 200,000 eggs a day

o leave human body with feces human waste as fertilizer, encourages the parasite

1. eggs hatch in the intestine– larvae burrow through the intestinal wall into blood or lymph

vessels– carried through the heart and lungs (cause damage)– eventually go back to the small intestine where they settle

and mature

Hookworm

• less than 1.5 cm• live in the human intestine• larvae hatch and feed on bacteria in the soil• host walks barefoot; microscopic larvae burrow into the skin;

then enter the bloodstream• move to the intestine for maturation• hook onto the lining of the intestine and suck the blood

Trichina Worm

• can live in pigs, rats, and bears• infection occurs in humans by eating raw or undercooked

meat• live in the small intestine• larvae migrate to the skeletal muscle and encyst• in order to survive the host needs to be eaten

o if not, the larvae are not freed from their cysts and eventually die

• cysts are calcified and remain in the muscleso cause stiffness

Pinworms

• found commonly in children• ingested by eating with hands contaminated with the small

eggs• live in the large intestine• female worms move to the anal region to deposit the eggs

o causes itchiness• the eggs may be distributed through the air and therefore

around the house

Reproduction

• sexual• Female: ovary, oviduct, uterus (fertilized

here)• Male:sperm cells made in the testis, sperm

cells pass through the spicule  • eggs deposited into the soil after fertilization