Unsegmented Worms

Flatworms

Belong to the phylum platyhelminthes. (Plat = flat) There are three classes: –Turbellaria –Trematoda –Cestoda

Characteristics of Flatworms They are acoelomates (they don’t have body cavities) They have bilateral symmetry Show cephalization Respiration through skin Single opening to digestive tract (pharynx)

Class Turbellaria Spade-shaped head and two eyespots Eat protozoans for scavenge Flame cells remove waste Are hermaphrodites (have male and female reproductive parts) Can reproduce by regeneration Are free-living

Class Trematoda Are parasitic flukes Have suckers on both ends of the body Can live inside or outside of host

Class Trematoda Nervous and excretory systems like turbellarians Hermaphrodites Have complex life cycles

Fluke Life-Cycles The long and complex life-cycle of the fluke can be made easier to understand through the use of a nonsense mnemonic : Every - Egg Mirror - Miracidium (free-living in water) Spotted - Sporocyst (in snail) Red - Redia (in snail) Certainly - Cercaria (free-living in water/snail) Met - Metacercaria (in 2nd intermediate host) Approval - Adult

Class Cestoda Parasitic Tapeworms Long, ribbon-like bodies Absorbs nutrients from host Hermaphrodites

Tapeworm Anatomy

Roundworms

Belong to phylum Nematoda Pseudocoelomates (fluid filled body cavity) Slender bodies that taper on both ends Have mouth and anus Can be free-living or parasitic

Pinworms live in human intestines

Trichinosis- a disease from eating infected pork

Cysts in Contaminated Pork

Rotifers Known as rotifers or wheel animals Transparent, free-swimming microscopic animal Freshwater & marine Have a ring of cilia around mouth that rotates like a wheel to bring in food Feed on unicellular algae, bacteria, & protozoa

Rotifers Have a muscular organ called the mastax behind the pharynx to chop food Nervous system composed of anterior ganglia & 2 long nerve cords Show cephalization (head end) Have 2 anterior, light- sensitive eyespots

Rotifer Anatomy