Classes of Aschelminthes Powerpoint Presentation

This presentation describes two classes of aschelminthes that are phylum nematoda and phylum kinorhyncha
This presentation gives us basic information of these two phylas.

1. CLASSIFICATION OF PHYLUM ASCHELMINTHES Class: ADP (ZBC)

2. PHYLUM NEMATODA The organisms belonging to the phylum Nematoda are also known as “roundworms”. There are 28000 species of Nematoda identified till date. They are unsegmented vermiform animals. The epidermis has dorsal and ventral nerve cords.

3. ORGAN SYSTEMS Digestive System : Nematodes have a complete digestive system comprising a mouth, pharynx, intestine, and anus. Food particles are ingested through the mouth and pass through the muscular pharynx into the intestine, where digestion occurs. Nervous System : Nematodes have a basic nervous system consisting of a nerve ring surrounding the pharynx and a ventral nerve cord. These structures help in sensory perception, coordination, and movement. Reproductive System : Nematodes reproduce sexually, and each individual possesses separate male and female reproductive structures. Males have specialized copulatory organs called spicules, while females have a uterus, ovary, and vulva.

4. CONT… Excretory System : The excretory system of nematodes consists of specialized excretory cells called excretory glands or canals. These structures help in osmoregulation and waste elimination. Muscular System : Nematodes have longitudinal muscles that run along their body, enabling them to move in a wriggling motion. These muscles also play a role in feeding and reproduction. Respiratory System : Nematodes lack a specialized respiratory system. Instead, gases are exchanged through their body wall via diffusion. Sensory Organs : Despite their small size, nematodes possess sensory organs such as papillae, amphids, and phasmids, which help them detect chemical cues, temperature, and touch.

5. REPRODUCTION Nematodes, also known as roundworms, exhibit diverse reproductive strategies within the phylum Nematoda. Here are some key aspects of their reproduction: Sexual Reproduction : Most nematodes reproduce sexually with separate male and female individuals. However, some species are hermaphroditic, possessing both male and female reproductive organs within the same individual. In such cases, they can either self-fertilize or cross-fertilize with other individuals . Nematodes practice internal fertilization, where sperm is transferred and fertilizes eggs inside the female's reproductive tract.

6. DEVELOPMENT Embryonic Development : After fertilization, the egg begins embryonic development. Nematodes undergo spiral cleavage, a type of cell division, resulting in a multicellular embryo. The embryo develops into a larva within the eggshell. Larval Stages : Nematodes typically go through several larval stages during their development. The number of larval stages can vary, ranging from three to more than five, depending on the species. Each larval stage resembles the adult form but is smaller and lacks reproductive structures. Molting : As nematodes grow, they outgrow their external cuticle, which is a protective covering. To accommodate their growth, nematodes shed their old cuticle in a process called molting. During molts, the nematode secretes a new cuticle and sheds the old one, allowing for continued growth.

7. CONT… Life Cycle Variation : The life cycle of nematodes can vary widely, depending on the species and their ecological niche. Some nematodes have direct life cycles, where the larvae simply mature and develop into adults. In contrast, others have more complex life cycles involving intermediate hosts or environmental stages. It's important to note that nematode life cycles can be influenced by various factors such as environmental conditions, host availability, and feeding habits. The specific details of reproduction and development may differ among the numerous species within the phylum Nematoda.

8. PHYLUM KINORHYNCHA Marine, microscopic worm-like. Superficial segmentation of body into 13 or 14 overlapping rings (Zonites). Body surface with spiny cuticle but no cilia. Mouth cone  or head protrusible and covered with  scalids . A pair of adhesive tubes in the front part of the ventral surface.

9. CONT… Pseudocoel with fluid containing amoebocytes. A nerve ring with a ventral cord with a ganglion in each Zonite. Eyespots in some.

10. I mportant N ematode P arasites of Humans Ascaris lumbricoides : Commonly known as the intestinal roundworm, Ascaris lumbricoides is one of the most common nematode parasites in humans. Infection occurs by ingesting eggs present in contaminated food, water, or soil. The adult worms reside in the small intestine, causing symptoms like abdominal pain, diarrhea, and weight loss. Trichuris trichiura : Also known as the whipworm, Trichuris trichiura is found worldwide. Infection occurs when humans ingest the eggs present in contaminated soil. The adult worms reside in the large intestine, causing symptoms like bloody stools, abdominal pain, and fatigue.

11. CONT… Enterobius vermicularis : Commonly known as the pinworm, Enterobius vermicularis is one of the most common intestinal parasites. Infection occurs by ingesting or inhaling the eggs, which are easily transmitted from contaminated hands, bedding, or clothing. The adult worms reside in the lower part of the small intestine and the cecum, causing symptoms like anal itching and disturbed sleep. Necator americanus and Ancylostoma duodenale : These two species are hookworms that can cause human infection. Larvae present in soil can penetrate the skin, usually through the feet, and migrate to the lungs. From there, they are coughed up and then swallowed, allowing them to reach the small intestine. Adult worms attach to the intestinal wall and feed on blood, potentially causing anemia, abdominal pain, and fatigue.