unsegmented worms. flatworms belong to the phylum platyhelminthes. (plat = flat) there are three...
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Unsegmented WormsUnsegmented Worms
Flatworms
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-CyclesThe long and complex life-cycle of the fluke can be made easier to understand through the use of a nonsense mnemonic :Every - EggMirror - 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
RoundwormsRoundworms
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