Nematodes PDF

KINGDOM : ANIMALIA SUBKINGDOM: METAZOA PHYLUM : NEMA THELMINTHES ‫شعبة الديدان االسطوانية‬ NEMATODA 1- Order : Ascaridata Ex. Ascaris 2- Order: Strongyleta Ex. Ancylostoma Ex. Ascaris  Class Nematoda (Round worms) General characteristics of the p...

KINGDOM : ANIMALIA SUBKINGDOM: METAZOA PHYLUM : NEMA THELMINTHES ‫شعبة الديدان االسطوانية‬ NEMATODA 1- Order : Ascaridata Ex. Ascaris 2- Order: Strongyleta Ex. Ancylostoma Ex. Ascaris  Class Nematoda (Round worms) General characteristics of the phylum: Triploplastic Acoelomata Bilaterally symmetrical Unsegmented Perivisceral cavity Single muscle layer Separate sex The alimentary canal open by mouth and anus Parasitic or free- living females usually larger than males Nematoda is a very large phylum occurs in nearly every habitats - Body cylindrical , bilaterally symmetrical , unsegmented 1/10 mm to 1 m in length. Usually with separate sexes ; Pharynx Mouth - free-living or parasitic , in plants Circum-pharyngeal nerve ring Excretory pore and animals Body structure: A nematode is a tube within tube , the outer is the body wall ; the inner is the alimentary canal ; the cavity between them is the pseudocoelom and contains the reproductive organs. Body covered with a tough flexible cuticle , molts 4 times during the life of a nematode to reach the adult stage Poctodaeum at the anterior end (head )there is a mouth surrounded by 6 lips (in parasitic forms fuse to give 3 lips ) oral cavity Leads pharynx ( triangular in cross section ) and pumps food into tubular intestine to short proctodaeum in female it opens to outside through an anus ; in males it joins the genital duct and both open to outside through a common cloaca. Body structure: Nervous system is a circum pharyngeal nerve ring from which 6 long longitudinal nerve cords extend posteriorly and 6 shorter nerve cords extend anteriorly towards the mouth No circulatory and respiratory systems Excretory system: excess water and metabolic wastes excreted by renette gland; opens by a ventral excretory pore behind the mouth. Reproduction : most nematodes have separate sexes , with paired reproductive organs in pseudocoelom. When mating , male introduces sperm to female vagina with the help of 2 spicules projecting from cloaca. Fertilization internal and female lays eggs. Young nematode hatches from egg and passes through 4 molts before reaching maturity https://www.studyandscore.com/studymaterial-detail/ascaris-male-reproductive-system-female-reproductive- Reproduction Male reproductive system: The male has one filamentous testicle, from which a larger vas deferens that leads to the vesicula seminalis It ends in a short muscular duct, the ejeculatory duct. The ejaculatory duct unites with the anal passage in the cloaca. On the dorsal side of the anal passage there are a pair of muscular sacs, the sac of the penisIt contains copulatory spicules Female reproductive organs lie in the posterior two-thirds of the pseudocoel and consist of ovaries, oviducts, uteri, and vagina. There are two ovaries. From the distal end of each ovary, there arises a thick, wider, and twisted oviduct. Each oviduct leads into a much wider, thicker, and almost untwisted tube, the uterus. At the anterior one-third of the body two uteri combine to form a short and highly muscular tube called a vagina, having an inner lining of the cuticle. https://www.studyandscore.com/studymaterial-detail/ascaris-male-reproductive-system-female-reproductive- Digestive system Life cycle: After mating a female Ascaris may lay eggs, the fertilized ovum is oval in shape contain one cell (zygote) and surrounded by a thin shell an inner coat and a thick brown shell at outer surface. Egg carried by the host's feces. Given suitable soil conditions, embryos develop into infective juveniles within 2 weeks. Direct sunlight and high temperatures are rapidly lethal, but the eggs have an amazing tolerance to other adverse conditions, such as desiccation or lack of oxygen. Infection usually occurs when eggs are ingested with uncooked vegetables or when children put soiled fingers or toys in their mouths. When a host swallows embryonated eggs, the tiny juveniles hatch. They burrow through the intestinal wall into veins or lymph vessels and are carried through the heart to the lungs. There they break out into alveoli and are carried up to the trachea. Not found circulatory system and respiratory system in Ascaris.