Nematode

• Nematodes are a type of helminths known as Nemahelminthes.
• Platyhelminthes are a type of helminths known as Flatworms.
• Trematodes are a type of helminths known as Fluke, which are flat, unsegmented.
• Cestodes are a type of helminths known as Tapeworms, which are flat, segmented.
• Nematodes are characterized by being elongated and cylindrical in shape, with bilateral symmetry, and are non-segmented.
• The anterior end of a nematode is rounded and the posterior end is tapered.
• Nematodes are light cream-white in color.
• The body wall of a nematode consists of the cuticle, hypodermis, and somatic musculature.
• The cuticle of a nematode is covered by a tough, elastic protective covering, is metabolically active and periodically undergoes molting, and also lines the buccal cavity, esophagus, rectum, cloaca, vagina, and excretory pore.
• The cuticle of a nematode has four layers: the epicuticle, exocuticle, mesocuticle, and endocuticle.
• The basal lamina is a structure that separates the cuticle from the underlying hypodermis.
• The hypodermis of a nematode is a thin, cellular structure that secretes the cuticle, protruding into the pseudocoelom along the mid-dorsal, mid-ventral, and lateral lines to form the longitudinal hypodermal cords where the hypodermal organelles are confined.
• The somatic musculature of a nematode is one or more layers of longitudinally arranged muscle cells.
• The pseudocoelom of a nematode is a cavity that contains fluid called hemolymph which bathes the internal organs, offering protection by acting as a cushion, and acts as a hydrostatic skeleton, providing support and rigidity.
• The digestive tract of a nematode includes a complete digestive tract with both oral and anal openings, consisting of the foregut, midgut, hindgut, and cloaca (male).
• The nervous system of a nematode consists of two major nerve centers, the circumesophageal commissure or nerve ring, ganglia from longitudinal nerves, rectal commissure, and ganglia from ventral longitudinal nerve.
• Parthenogenetic nematodes develop a female (rarely a male) gamete (sex cell) without fertilization, this is known as asexual reproduction.
• Adult female nematodes can be oviparous, viviparous (larviparous), or parthenogenetic.
• The mode of transmission of nematodes includes ingestion of embryonated egg, ingestion of infective larvae, skin penetration, and autoinfection.
• Phasmids are a class of nematode containing sensory organs at the caudal end.
• Some nematodes are parthenogenetic: males are smaller than females, males are curved posteriorly, females are flat posteriorly.
• Aphasmids are a class of nematode containing sensory organs at the anterior end.
• Sexes in nematodes are separate: dioecious.
• Larval stages are present in some nematodes.
• Trichinella spiralis, Trichuris trichiura, Capillaria philippinensis are examples of aphasmids.
• Viviparous nematodes bring forth live young that have developed inside the body of the adult female nematode.
• The ova stage is the infective stage in nematodes.
• The larva stage is the infective stage in nematodes.
• The male reproductive organ of nematodes consists of a single tubule, one or two testes, its smaller end, which extends into a vas deferens and seminal vesicle, terminates in an ejaculatory duct opening into the cloaca, and is associated with one or more chitinized copulatory spicules.
• Hookworms, Ascaris lumbricoides, Strongyloides stercoralis, Enterobius vermicularis are examples of phasmids.
• Chemoreceptors are located anteriorly in amphids and posteriorly in phasmids.
• The female reproductive organ of nematodes is usually didelphic, containing two cylindrical ovaries which expand into uteri, the uteri unite to form a common vagina, and are associated with a single gonophore or vulva.
• The excretory system of nematodes includes renettes, which are large unicellular glands that empty through an excretory pore.
• The adult stage is the diagnostic stage in nematodes.
• Oviparous nematodes produce egg, and the young hatches after being expelled from the body.
• The habitat of adult worms in hosts can include the small intestine, large intestine, tissue, and skin.
• Mechanoreceptors are located around the mouth of a nematode, and include labial papilla and cephalic papilla.
• Piperazine is a treatment for partial intestinal obstructive due to parasite bolus, acting as a GABA receptor agonist.
• War on Worms (WOW) is a prevention and control strategy for parasitic worms, involving surveillance and monitoring of stool using Kato-Katz method, and reinfection usually occurs 4 months post-treatment.
• Trichuris trichiura, also known as whipworm, is a soil-transmitted helminth (STH) along with Ascaris lumbricoides and hookworms, with a worldwide distribution and common in tropical regions with poor sanitation.