Phylum Platyhelminthes flatworms Prepared by Nada H Lubbad

Phylum Platyhelminthes ( flatworms ) Prepared by : Nada H. Lubbad

Ø General characteristic: o Metazoa. o Triploblastic : - Ectoderm - Mesoderm - Endoderm o Acoelomate. o Bilaterally symmetrical, and dorsoventrally flattened (flat worms ) , cephalization was established. o Free-living or parasites ( both ecto-and endoparasites). o Usually hermaphrodite, The individual produces the male as well as the female gamete, Sexes are present together. Platyhelminthes Turbellaria Trematoda Cestoda

v Class Turbellaria: o Free-living , mostly marine organisms and freshwater. o Ciliated glandular epidermis. o Mouth ventral and posterior in position. o Most move by means of cilia and mucous. o Muscle contractions also permit turning, twisting and folding of the body. o Turbellarians are carnivores and prey on other animals or eat dead animal remains (scavenge). o They have well developed sensory structures, including eyespots, mechanoreceptors, and chemoreceptors

Ø Planaria External features

Internal features

T. S of Planarian

v Class Trematoda o Flukes are parasites. o Leaf like body without ciliated epidermis in the adult, but covered by a thick tegument. o They have a suckers, which they cling to the body of the host. o They have 2 -branched alimentary canal with an anterior mouth. o They are divided into two subclasses: - Monogenea, ectoparasites and develop directly on a single type of host. - Digenea, endoparasites and develop in more than one host.

Ø Fasciola: liver fluke o Fasciola hepatica , Digenea. o Have to suckers : oral and ventral o They live in the bile ducts of cattle , feeding on the bile and causing the disease known as “ liver rot “ as a result of the irritation caused by their surface spines.

Ø Schistosoma (Bilharzia): Blood flukes o Digenea. o It causes schistosomiasis or bilharziasis. o The life history is similar to Fasciola, but lacks the redia stage. o Schistosoma haematobium, lives in venous vesical plexus and drops its egg in the venules of urinary bladder to pass out with urine. - sexes are separate. - the intermediate hot is a freshwater snail called Bulinus truncatus

Schist. Haematobium egg

v Class Cestoda o Tapeworms, endoparasites and lack alimentary canal. o They have a great power of reproduction, both asexual and sexual. o Taenia, posses defining characteristics: proglottides , suckers with hooks. o T. saginata (beef tapworm) , T. solium (pork tapeworm) both infect man. o Hermaphrodite , each proglottis develop both sets of genital organs. o Self fertilization , occurs within the same proglottis or cross fertilization between different proglottides of the same or other worms.