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Nematoda By Liviu, Ross, and Yuchen Ross.

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1 Nematoda By Liviu, Ross, and Yuchen Ross

2 Overview Nematodes are slender worm-like animals that are usually microscopic, but can grow to as long as 2 inches, or even a meter, long. Their bodies will often have ridges, rings, warts, bristles, hooks, etc. The main difference between nematodes (roundworms) and all other worms is that these are NOT SEGMENTED. Ross

3 Phylum & Sample Animals Phylum: Nematoda Sample animals: Roundworms. Thats it. Metazoa: Animals with fixed body plan –Eumatzoa: All animals but sponges Bilateria: Bilaterally Symmetric /roundworm.jpg Ross

4 Body Cavity and Symmetry Body Cavity - Nematodes have fake body cavities and thus are called Pseudocoelomate. The cavity is partially lined by tissue derived from the mesoderm. The other is separated by the digestive cavity that is not derived from the mesoderm. They are bilateral - if you cut them from the mouth you can only get one plane of symmetry. Think worms. Yuchen

5 Circulatory and Nervous System They DO NOT have a circulatory system ;_; They DO have an Nervous system which form an central ring near the anterior end of the nematode that forms a pseudo-brain. The rest is 4 nerve chords that run along the 4 sides (dorsal, ventral and laterals) of the worm. The dorsal is responsible more motor control while the laterals are for sensory. The thickest chord ventral combines the two functions. Yuchen

6 Digestive System Food enters and exits the worm in this order: oral cavity, pharynx, intestines, anus Roundworms have no stomach The oral cavity is coated with a tough material called cuticle Ross

7 Excretory System Longitudinal excretory ducts. The waste is simply filtered through these ducts and taken outside of the worm. In simpler species, a unicellular gland called a renette cell pumps out toxins through an excretory pore. Ross

8 Muscle System/Locomotion Underneath the epidermis lies a layer of muscle cells. These muscles are longitudinal (test question), meaning that they are unable to elongate the body and do not inch like earthworms or snakes do. Their movement is characterized by alternating contractions of the muscle, which looks like a thrashing or a wagging tail. Ross

9 Skeletal Type The cuticle is the closest thing a roundworm has to a skeleton because the cuticle is used for movement and support. There are no distinct joints. Ross

10 Sensory structures/features Sensory Bristles along the cuticle. (sensilla) Sensory organs at posterior, involved in reproduction. (phasmids) Two Amphids located on the head Amphids: Specialized Sensillia that can sense better than normal ones on the cuticle Bibliography for this slide: 11.1 Created by Livius Cesar Cengher Liviu Cengher

11 Both sexes possess one or two tubular gonads In males, the sperm are produced at the end of the gonad, and migrate along its length as they mature. In females, the ovaries each open into an oviduct and then a glandular uterus Male Rep. Organ Female Rep. Organ Bibliography for this slide: Liviu Cengher Reproduction

12 Gas exchange Diffusion across the cuticle. O2, CO2, ETC. Semi Permeable Cuticle O 2 CO 2 Bibliography for this slide: Liviu Cengher

13 Other unique features, sketches They have a tough Cuticle (a mass of cellular material and nuclei without separate membranes that coats the body) which is periodically shed. The word "nematode" comes from a Greek word Νεμα (Nema), which means "thread. Nematodes are able to suspend their life processes completely when conditions are unfavorable, then return to life when favorable conditions return. This is called cryptobiosis. Bibliography for this slide: * PowerPoint Clipart * * * ** * Liviu Cengher

14 Pictures Ross

15 Test Question 1 Food is processed in nematodes in which order? a.Pharynx, stomach, intestines, anus b.Oral cavity, pharynx, stomach, excretory ducts c.Pharynx, intestines, excretory ducts d.Oral cavity, intestines, anus e.Oral cavity, pharynx, intestines, anus Ross ANSWER: E.

16 Test Question 2 Nematodes have all of the following systems EXCEPT a.Excretory b.Circulatory c.Skeletal d.Nervous e.Digestive Ross ANSWER: B.

17 Test Questions 3 & 4 Which of these breathe through their tough cuticle? a.Onychophora b.Arthropoda c.Nematoda d.Mollusca Which of these feel through sensillia on their tough cuticle? a.Nematoda b.Brachiopoda c.Cnidaria d.Annelida Liviu Cengher 3. C 4. A (because our ppt is on nematodes obviously) Those Things

18 Bibliography Info: Pictures: 11.1 Created by Liviu Cengher * PowerPoint Clipart Liviu Cengher

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