Ch. 10 Platyhelminthes (flatworms) Characteristics • Simple organ systems • 1mm to 25 meters long • 4 classes • Flat bodies Characteristics • Reproduction- sexually or asexually. Planaria use fission. Tapeworms form chains Echinodermata Uniramia Chordata Lophophorates Chelicerata Protochordates Crustacea Arthropoda Hemichordata Annelida Mollusca Other pseudocoelomates Nemertea Platyhelminthes Nematoda Ctenophora Cnidaria Mesozoa Placozoa Sarcomastigophora Ciliophora Porifera Apicomplexa Microspora Myxozoa Class Turbellaria • Ex: Planaria • Free living. Some in fresh and some salt water. Beating cilia create turbulence in water. • Predators & scavengers. Carnivores. • Food gets sucked into intestine. Waste goes back out through pharynx. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Turbellaria Sense Organs • Auricles- look like earlobes. Have chemoreceptors for food location. • Ocelli- light sensitive eyespots Class Monogenea • Ex: Flukes • Single Host- eggs hatch, then attach. • External parasites (mainly on fish, some frogs, turtles) • Usually don’t harm host Class Trematoda • Ex: Flukes • Parasites of vertebrates (as adults) • Complex life cycle- many intermediate stages. • Usually “shelled eggs” leaves host in excrement & reaches water to develop further. Class Cestoidea • Ex: Tapeworms • Parasites inside vertebrate digestive system. • Lack mouth & digestive tract. Absorb nutrients through body wall (tegument). Class Cestoidea • Scolex- suckers & hooks for attachment to host intestine. • Proglottids- reproductive segments (in a chain). • Requires at least two hosts. Scolex Proglottid Testes Uterus Vas deferens Seminal receptacle Ovary Yolk gland Class Cestoidea • Reproduction: new proglottids form behind scolex. Cross fertilize. Shelled embryos expelled through uterine pore. • OR, entire proglottid breaks off. Worm movies on Notebook.