Flatworms and Roundworms

ANCESTRAL PROTIST Porifera Ctenophora Cnidaria Acoela True Tissues Metazoa Eumetazoa Bilateria Hemichordata Echinodermata Chordata Platyhelminthes Rotifera Ectoprocta Brachiopoda Mollusca Annelida Nematoda Arthropoda Deuterostomia Lophotrochozoa Ecdysozoa Single common animal ancestor protostomes invertebrates Bilateral at some point Usually cephalized Triploblastic development

Terms of location (for bilateral organsims)

FLATWORMS (phylum platyhelminthes) Flattened body plan – Puts all cells close to ext. env. or GVC – No need for respiratory or circulatory systems – Gas exchange across ext. surface and gastrodermis Free living Parasitic forms Aceolomates (no body cavity) Most belong to Rhabditophora

Digestive System Gastrovascular Cavity—incomplete digestive system Highly branched (diverticula) Functions – Digestive chamber most digestion occurs extracellularly – distributes nutrients

Excretory System & Water Balance Protonephridia flame bulbs  internal  external env. through pores In freshwater species for maintaining water balance Some parasitic flatworms are isotonic with host and protonephridia eliminate nitrogenous waste

Interstitial fluid  cap cell of flame bulb  eliminated via ducts and pores

Nervous System: – Dual ventral nerve cords – “brain of ganglia” Reproduction; – Mostly cross fertilizing hermaphrodites – Some parasitic forms are dioecious CNS

Planaria free living Rabditophora FREE LIVING RABDITOPHORA predators and scavengers move w/ ventral cilia & mucus Sense Organs & NS – Photoreceptors (eyes) – Lateral flaps (auricles) that are chemoreceptor's

Trematodes Intermediate and final (ultimate) host – Blood flukes (schistosoma), liver flukes epicuticle of proteins and lipids instead of epidermis – digestion by the digestive enzyme in hosts

Schistosoma: unique among trematodes; are dioecious with distinct sexual dimorphism Large male that surrounds female Female is enclosed within the males gynacophoric canal for entire life of worms where they reproduce sexually.

Figure Human host Male Female 1 mm Mature flukes Ciliated larva Motile larva Snail host

Tapeworms Mostly inside vertebrates Scollex for attachment No GVC; direct absorption of nutrients Proglottids = reproductive segments Reproduction is usually sexual between proglottids of adjacent individuals

Tapeworms

Roundworms (phylum Nematoda) Bilateria-protostoma-ecdysozoa Cyclinderical shaped bodies that taper to tips at both ends Psuedocoel Usually dioecious Free living in soil, fresh, and salt water – decomposers: important ecological role as decomposers Many important parasitic forms – Parasitize crop plants – Parasitize humans (~50 species) e.g., trhinella spiralis—trichinoisis – Parasitize non-human animals – Parasitic forms manipulate host cells

BODY COVERING Cuticle (collagen based) that must be shed – Ecdysis/molting GAS AND WASTE EXCAHNGE Directly across body wall (gas & nitrogenous wastes) Some species w/ glands to excrete salt No circulatory system Nutrients transported by fluid in psuedocoel.

Digestive System Complete digestive tract (alimentary canal) Continuous feeding Specialized regions/organs – Mouth, sucking pharynx, intestines, rectum, anus – Contents propelled by body movements

Nervous system 4 nerve cords + “brain” of neuron cluster surrounding pharynx. ventral nerve largest Muscles: Longitudinal muscles only Psuedocoel acts as a hydrostatic skeleton

Schistosomiasis, also known as bilharzia, snail fever, and Katayama fever Schistosomiasis affects almost 210 million people worldwide, [5] and an estimated 12,000 [6] to 200,000 people die from it a year. [7] The disease is most commonly found in Africa, as well as Asia and South America. [3] Around 700 million people, in more than 70 countries, live in areas where the disease is common. [7][8] Schistosomiasis is second only tomalaria, as a parasitic disease with the greatest economic impact. [9] It is classified as a neglected tropical disease. [10] [5] [6] [7]AfricaAsiaSouth America [3] [7][8]malaria [9]neglected tropical disease [10]