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.
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/Physiolo gy/repstrat.htm) No respiratory or circulatory systems
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.
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
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.
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.
The gut tube comprises a mouth, a muscular pharynx, non-muscular intestine, a short rectum and a terminal anus. The cylindrical pharynx has The relaxation of muscles close radial muscles that insert on the pharyngeal lumen and the cuticular lining of its forces the food posteriorly lumen and on a basement toward the intestine. membrane. When muscles in the anterior of the pharynx contract, they open the lumen and suck food inside.
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.
Large human roundworm (parasites ofhuman).Ascaris Suum found in pig and have samemorphologically similar as in human.Female of both species : up 30 length and canproduce 200000 egg a day.Adult : occupy a small intestineEgg : leave host body in feces.
Extreme resistance to adverse conditionInfection by: Ingestion of ova containingembryos in contaminated food.Effects; alveoli : cause pneumonia intestine : abdominal symptoms and allergicreaction, in large number can block intestine.
Hookworms are so named because theirinterior end curves dorsally, suggesting a hook.Most common species is a Necator americanus(L.necator,killer) whose female are up to 11 mmand male 9mm in length.They suck blood and pump it through theirintestine, partially digesting it and absorbingthe nutrients.
Infection by ; contact with the soil infestedwith juveniles that burrow into the skin.Effects ; cause anemia, mental retardation inchildren, physical growth and general loss ofenergy.
Trichinella spiralis tiny nematode thatresponsible for the potential lethal diseasetrichinosis.Adult worm burrow in the mucosa of the hostsmall intestine, where females produce livingjuvenilesJuveniles penetrate blood vessel and carriedthroughout body then penetrate in skeletalmuscle cells.
Infection by; ingestion of infected musclesEffects; - juveniles cause astonishing redirection ofgene expression in host cell, which loses itstriation and become nurse cell. - heavy infection may cause death.
Cause relatively little disease, but they are themost common in the United States.Length about 12 mm.Migrate to anal at night to lay eggs, eggsdevelop rapidly and become infective within 6hours at room temperature.
Adult occupy large intestine and cecum.Haplodiploidy ; male is haploid producedparthenogenetically and female is diploid arisefrom fertilized egg.Infection by; Scratching the resultant itcheffectively contaminates hands and bedclothes.
Brugia malayi and etcInfect the lymphatic system, and females may be100 mm long.Females worm release tiny microfilariae into theblood and lymph of the host.Microfilariae ingested by mosquitoes and developto the infective stages and can be transmitted bymosquito to new host.Long and repeated exposure can causeelephantiasis.Another filarial worm causes river blindnesscarried by blackflies.