RIDWAN BIN SHAMSUDINMARIAMAH BINTI ARON

PHYLUM NEMATODA: ROUNDWORMS

The most important phylum of parasitic animal groups

Nematodes are the most smallest ecdysozoan animals.

The habitat in the sea, in fresh water and in soil. Good topsoil may contain billions of nematodes per acre.

Nematodes parasitize virtually every type of animal and many plants.

Introduction…

Unique sensory amphids or phasmids Body bilaterally symmetrical Triploblastic body Digestive system completed Body wall has longitudinal muscles Sensory system includes papillae and

setae for touch Parthenogenesis occur rarely (http://

plpnemweb.ucdavis.edu/nemaplex/General/Physiology/repstrat.htm)

No respiratory or circulatory systems

General characteristics

Most nematodes are 5 cm long, and many are microscopic but some parasitic nematodes are over a meter in length.

The outer body is covering by non-cellular cuticle which are secreted by the hypodermis.

The most conspicuous feature of nematodes is the present of pseudocoelom that act as a hydrostatic skeleton.

Form and functions…

Pseudocoelomate…

Structure of nematodes

Structure of nematodes

Layers of the cuticle is composed of collagen.

Function:- The cuticle is a multi-functional exoskeleton. It is a highly

impervious barrier between the animal and its environment. It is essential for maintenance of body morphology and integrity.

- Plays a role in locomotion via attachments to body-wall muscles

Cont…

The longitudinal muscles arranged in 4 bands that projects inwards to the pseudocoelom.

The body wall muscle in nematodes is that the muscle extend to processes to synapse with nerve cord rather than nerves extending an axon to synapse with muscle.

The fluid filled pseudocoelom constitutes a hydrostatic skeleton.

Cont…

Parasitic nematodes are obligate aerobes.

The parasitic nematodes have an energy metabolism; a Krebs cycle and cytochrome system.

Nematodes derive energy through glycolysis and some additional electron-transport sequences.

Cont…

The gut tube comprises a mouth, a muscular pharynx, non-muscular intestine, a short rectum and a terminal anus.

Digestive system

The cylindrical pharynx has radial muscles that insert on the cuticular lining of its lumen and on a basement membrane.

When muscles in the anterior of the pharynx contract, they open the lumen and suck food inside.

The relaxation of muscles close the pharyngeal lumen and forces the food posteriorly toward the intestine.

Most nematodes are dioecious. Males are smaller than females. Fertilization is internal, and shelled

zygotes or embryos and stored in the uterus until deposition.

There are four juvenile stages, each separated by a shedding of the cuticle.

Many parasitic nematodes have free living juvenile stages and others require an intermediate host.

Reproductive system

http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html

http://www.earthlife.net/inverts/nematoda.html

http://www.niaid.nih.gov/topics/parasiticroundworm/pages/default.aspx

http://www.umm.edu/altmed/articles/roundworms-000144.htm

An extra information…

Nematode parasites…

Ascaris lumbricoidesTrichina wormHookwormsPinwormFilarial worm

ASCARIS LIMBRIOCOIDESLarge human roundworm (parasites of human).Ascaris Suum found in pig and have same morphologically similar as in human.Female of both species : up 30 length and can produce 200000 egg a day.Adult : occupy a small intestineEgg : leave host body in feces.

Extreme resistance to adverse conditionInfection by: Ingestion of ova containing embryos in contaminated food.Effects;

alveoli : cause pneumonia intestine : abdominal symptoms and

allergic reaction, in large number can block intestine.

Cont..

HOOKWORMS

Hookworms are so named because their interior end curves dorsally, suggesting a hook.Most common species is a Necator americanus (L.necator,killer) whose female are up to 11 mm and male 9mm in length.They suck blood and pump it through their intestine, partially digesting it and absorbing the nutrients.

Infection by ; contact with the soil infested with juveniles that burrow into the skin.

Effects ; cause anemia, mental retardation in children, physical growth and general loss of energy.

Cont..

TRICHINA WORM

Trichinella spiralis tiny nematode that responsible for the potential lethal disease trichinosis.Adult worm burrow in the mucosa of the host small intestine, where females produce living juvenilesJuveniles penetrate blood vessel and carried throughout body then penetrate in skeletal muscle cells.

Infection by; ingestion of infected musclesEffects;

- juveniles cause astonishing redirection of gene expression in host cell, which loses it striation and become nurse cell.

- heavy infection may cause death.

Cont..

PINWORMS

Cause relatively little disease, but they are the most common in the United States.Length about 12 mm.Migrate to anal at night to lay eggs, eggs develop rapidly and become infective within 6 hours at room temperature.

Adult occupy large intestine and cecum.Haplodiploidy ; male is haploid produced parthenogenetically and female is diploid arise from fertilized egg.Infection by; Scratching the resultant itch effectively contaminates hands and bedclothes.

Cont..

FILARIAL WORMS

Brugia malayi and etcInfect the lymphatic system, and females may be 100 mm long.Females worm release tiny microfilariae into the blood and lymph of the host.Microfilariae ingested by mosquitoes and develop to the infective stages and can be transmitted by mosquito to new host.Long and repeated exposure can cause elephantiasis.Another filarial worm causes river blindness carried by blackflies.

Elephantiasis disease