BIOL 3454 1nd Edition Lecture 19 I II Smaller Ecdysozoans Phylum Nematoda a 25 000 species and probably many more b Live everywhere c Especially abundant in topsoil d Parasitic and on nearly everything e Species Caenorhabditis elegans is the model organism in developmental biology f Every cell in the body traced from its origin to final state g Hugely economically important to agriculture medicine h Above bacteria but still microscopic i Form and function i Eutely fixed number of somatic cells ii Cylindrical shape iii Flexible nonliving cuticle like epidermis of skin iv No motile cilia or flagella except in one species v No protonephridia excretory system made of glands emptying into a pore simple vi Muscular pharynx vii Most less than 5cm a few over 1m j Covering and body structure i Thick noncellular cuticle secreted by a hypodermis ii Mostly made of collagen iii Contains the hydrostatic pressure iv Protects the worm from dessicattion v No circular muscles only longitudinal fixed length vi Each muscle has a contractile fibrillar portion and a noncontractile sarcoplasmic portion vii Each cell body has a muscle arm that extends to the central or dorsal nerve viii Fluid filled pseudocoelom gut tube not lined with mesoderm k Nematode digestion and metabolism i Mouth muscular pharynx a long nonmuscular intestine rectum and anus ii Intestine only one cell layer thick easy short distance iii Defecation by muscles pulling the anus open high hydrostatic pressure simply forces waste out iv Many have anaerobic metabolism no krebs and or cytochrome cycle glycolysis fermentation v Some obligate aerobes and have the corresponding cellular machinery l Nerves and reproduction i Ring of nerve tissue around pharynx These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute m n o p q ii Gives rise to both dorsal and ventral nerve cord iii Sensory papillae clustered around head iv Pair of better sense organs called amohids that open on each side of the head in parasitic forms they called phasmids deep cellular pit with cilia v Most dioecious males usually have a pair of copulatory spicules fertilization internal eggs stored in uterus until deposition vi 4 juvenile stages each separated by a cuticle molt vii Hooked end is male Ascaris lumbricoides species i Commonly used in labs bc of size and availability ii Very common iii Highly parasitic on humans some countries in the southeastern US have a 25 infection rate iv 200 000 eggs a day v Eggs are ingested on uncooked vegetables or from putting unwashed hands in mouth vi Life cycle 1 Host swallows eggs 2 Eggs hatch burrow through intestinal wall into veins or lymph vessels migrate to lungs through circulatory system 3 Break out of lungs crawl up trachea are swallowed 4 Go through stomach mature in intestine about 2 months after hatching hookworms i anterior ends curves dorsally ii large plates in mouth cut into intestinal wall iii suck blood pump through intestine iv extreme cases can cause growth problems v eggs pass in feces juveniles hatch in soil live on bacteria juveniles leave soil and burrow into skin when contract is made go through lungs into digestive tract Trichina sp i One of many species causing trichinosis ii Adult worms burrow in lining of intestine release living young juveniles penetrate blood get everywhere encyst intracellulary you get it from eating uncooked meat iii Only about 10 20 infections a year in the US iv Have a domestic life cycle and a sylvatic life cycle Filarial worms i Heart worms ii Many specieas names nc females release live young called microfilariae into circulatory system iii Some cause elephantitis after long and repeated exposure other cause river blindness get stuck in lymph nodes and cause deformation iv Most commonly known in US is the dog heartworm and spread by mosquitos Monsters inside me worm in my butt i Over eating weight loss ii Body cleanse iii iv v vi Stomach pain gassy Found worm coming out of butt 9 long Got it in Iraq and Anfganistan Treatment anti parasitic medication