Invertebrates Worms PDF

Invertebrates Worms  Kingdom: ANIMALIA PROTOZOA METAZOA kingdom : Prototista Eg : Ameoba PARAZOA EUMETAZO PHY : PORIFERA A...

Invertebrates Worms  Kingdom: ANIMALIA PROTOZOA METAZOA kingdom : Prototista Eg : Ameoba PARAZOA EUMETAZO PHY : PORIFERA A Eg : Sponges DIPLOBLASTIC RADIATA TRIPLOBLASTIC PHY : COELENTERATA BILATERIA Eg : Hydra Acoelomata Pseudocoelomata EUCOELOMATA Phy : Platyhelminthes Phy : Aschelminthes(nematoda) Eg : Ascaris Phy : Phy : Phy : Phy : PHY : Annelida Arthropoda Mollusca Echinodermata CHORDATA  Comparison of Body Organization of Flatworms, Roundworms, and Earthworms ( for differentiation of Coelom) ectoderm: blue mesoderm: red Flatworm endoderm: yellow Platyhelminthes acoelomate Roundworm Nematoda pseudocoel. Earthworm Annelida coelomate  IV- Helminthes= Worms A- Platyhelminthes (Flat worms) B- Nematoda (Rounded worms)  HELMINTHS Characteristics 1- Eukaryotic, multicellular animals that usually have digestive, circulatory, nervous, excretory, and reproductive systems. 2-Triploblastic animal (endoderm, mesoderm and ectoderm). 3- Worms with bilateral symmetry, head and tail, and tissue differentiation. 4-The parasitic forms may have more than one hosts.  5- Parasitic helminths spend most or all of their lives in or on host and usually have the following specializations: a -Have suckers, spins, hooks or lips for attachment. b - May have a digestive system (Trematods, nematods) or not (Cestods), absorb nutrients from host’s food, body fluids, or tissues. c- Have a reduced nervous system. d- Locomotory organs may reduced or absent. e- Sex separate or fused (hermaphrodite ), the reproductive system may be complex. f- The worms may produce hundreds or thousands of eggs  Helminths Life Cycle Extremely complex Intermediate hosts harbor larval (developmental) stage. Definitive host harbors adult stage. Sexual reproduction strategies: ◦Dioecious (sex separate): Male and female reproductive organs are found in separate individuals. ◦Monoecious (Hermaphroditic): One animal has both male and female sex organs. Most hermaphrodites copulate with other animals (cross - fertilization), a few copulate with themselves (self- fertilization).  Platyhelminthes Acoelomates - thin solid bodies Bilateral symmetry Approx. 14,500 species Platyhelminthes may be: Free (Live in salt and freshwater) 1- Class Turbellaria (Planarians) Parasitic as: 2- Class Trematoda- (Flukes) 3- Class Cestoda (Tapeworms) Flukes The digestive system The worm begins and attaches to host with two suckers: oral sucker (anterior) with mouth. The other sucker is the acetabulum ( ventral sucker). The mouth opens to pumping pharynx. Digestive tract divides into two blind pouches called cecae Mostly feed on host cells and cell fragments cecae Digestion and Nutrition Most are carnivores May eat small invertebrates, scavenge, dead animals Taken food via the pharynx on the ventral side, which can be extended (Turbellaria) or contracted in other species Gastrovascular cavity (digestive cavity, gut) may be unbranched or branched (and is absent in some genera) Digestion is partially external and partly internal  The excretory system Turbellarians have several specialized organs/cells involved in osmoregulation. Protonephridia are networks of tubules along the length of the body in parenchyma tissue (middle layer, a spongy mass of mesoderm cells). Flame cells are tiny, hollow enlargements at the tips of these tubules with beating cilia that create negative pressure. Pressure draws water into tubules, where it exits body via nephridiopores. The excretory system  Reproducti on 1- Asexual reproduction by:. Transverse fission in Planarian (divide into anterior and posterior individuals).. Although uncommon in nature, many planarians can regenerate most of their body from a small piece. This is termed regeneration. 2-Sexual reproduction; Most are monoecious (cross or self internal fertilization).  Have internal fertilization, sperm exchange between copulating animals. Eggs are deposited in cocoons Larvae usually resemble adults, but may spend some time as a free swimming larval stage. Classification of Platyhelminths Free living- a) Class Turbellaria (planarians) mostly predators Parasitic – b) Class Trematoda (internal flukes) exclusively parasitic complicated life-cycles c) Class Cestoda (tapeworms) exclusively parasitic  a) Turbellaria General Characteristics ~3,000 species  Free-living, bottom dwellers in freshwater and marine environments (plus a few tropical terrestrial species) eyespots sense light on “Spade” shaped head.  Range in size from