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Biology 11 – Kingdom Animalia Study of the Primitive Worms Phylum Platyhelminthes: Flatworms Phylum Nematoda: Roundworms BIOL 316 Phylum Platyhelminthes 1 Phylum Platyhelminthes – the Flatworms The Planarians The Tapeworms The Flukes BIOL 316 Phylum Platyhelminthes 2 Importance of the Flatworms to Evolution Bilateral body plan – left side mirror image of right Cephalization – development of the head sense organs and nerves concentrated in head region Centralization of nervous system: Nerve cord accompanies cephalization and bilateral symmetry. Advanced muscle tissue present; Primitive excretory system allows removal of metabolic wastes BIOL 316 Phylum Platyhelminthes 3 BIOL 316 Phylum Platyhelminthes 4 Phylum Platyhelminthes Characteristics Bilateral symmetry; anterior and posterior ends. Body flattened Well developed Epidermis No internal body cavity other than digestive tube (acoelomate) Parenchyma (connective tissue) fills space between organs. Incomplete digestive system Still one opening This critter eats and poops out of its mouth – mmmm, pass the popcorn BIOL 316 Phylum Platyhelminthes 5 Flatworm Nervous System and Excretory System Characteristics Nervous system with ganglia and longitudinal nerve cords and branches Simple sense organs; eyespots in some. Excretory system Lack circulatory, respiratory, and skeletal systems. Reproductive system complex; Well-developed gonads and accessory organs. Free-living (eg Planarians) have well developed digestive and nervous systems to seek-out and process food Parasitic Tapeworms – rely on host’s digestive system to process food, which absorb. No need for advancement of nervous system – not needed. BIOL 316 Phylum Platyhelminthes 6 Nervous System and Sense Organs Have a Nerve-net. Most have more complex system. Cerebral ganglion = primitive brain coordinates impulses. “Ladder” system carries impulses throughout body Many sense organs present Eyespots Chemoreceptors, touch sensors and rheoreceptors (sense direction) also common BIOL 316 Phylum Platyhelminthes 7 BIOL 316 Phylum Platyhelminthes 8 BIOL 316 Phylum Platyhelminthes 9 Advantage of Being Flat Surface area to volume ratio is important for organisms. 3mm many substances enter and leave through body surface. 3mm 3mm Volume = 3 x 3 x 3 = 27mm2 Area = 6(3 x 3) = 54mm3 Faster absorption and release of wastes 9mm 3mm 1mm Volume = 9 x 3 x 1 = 27mm2 Area = 2(9 x 1) + 2(3 x 1) + 2(3x9) = 78mm3 BIOL 316 Phylum Platyhelminthes 10 Cross Section of a Flatworm BIOL 316 Phylum Platyhelminthes 11 Nutrition and Digestion Typical digestive system includes a mouth, a pharynx, and an intestine. Parasitic Tapeworms and Flukes lack a digestive system Free living flatworms (Planarians) are carnivorous; suck prey into pharynx with mouth. Undigested food goes out mouth. Yes, folks, they eat and excrete out the same hole Parasitic flatworms, such as the Tapeworm absorb molecules from host. BIOL 316 Phylum Platyhelminthes 12 Reproduction – in Free-living Flatworms such as Planarians May reproduce sexually or asexually Asexual: Binary fission – split in two Sexual: Both sexes present in same flatworm (hermaphrodites). Fertilization internal, eggs produced Embryos emerge as juveniles resembling adults. BIOL 316 Phylum Platyhelminthes 13 Reproduction in theTapeworm! Lack digestive system Sucker and hooks on anterior end for attachment Neck produces new segments Called proglottids Each proglottid contains male and female gonads Reproductive output high Many proglottids per worm Many eggs per proglottid BIOL 316 Phylum Platyhelminthes 14 BIOL 316 Phylum Platyhelminthes 15 BIOL 316 Phylum Platyhelminthes 16 Tapeworm - Life Cycle BIOL 316 Phylum Platyhelminthes 17 Flukes -- Life Cycle of a Liver Fluke BIOL 316 Phylum Platyhelminthes 18 The Coelom or Body Cavity Advances BIOL 316 Phylum Platyhelminthes 19 Another Look at the Coelom BIOL 316 Phylum Platyhelminthes 20 Roundworms Phylum Nematoda Non-segmented; have smooth body wall Generally colorless, less than 5 cm in length, occur almost everywhere Parasitic roundworms Live anaerobically in every type of animal and many plants Have tube-within-a-tube body plan Digestive tract is complete; has both mouth & anus BIOL 316 Phylum Platyhelminthes 21 BIOL 316 Phylum Platyhelminthes 22 BIOL 316 Phylum Platyhelminthes 23 Roundworm Ecological Roles Carnivores that catch and eat algae, fungi, decaying matter Recyclers Parasites of Plants – eg. The Golden Nematode attacks potato crops, causing severe devastation Parasites of animals - BIOL 316 Phylum Platyhelminthes 24 Ascaris – Parasitic Roundworm of Pigs and Humans BIOL 316 Phylum Platyhelminthes 25 Unfortunately, they can Grow quite Big! BIOL 316 Phylum Platyhelminthes 26 BIOL 316 Phylum Platyhelminthes 27 Parasites: Your Pet's Enemies Tiny parasites that pose a gigantic threat Heart worms inside the dog's heart, can grow to a length of 14". What they do: Restrict blood flow and cause organ damage. Symptoms include coughing. labored breathing, heart failure. Untreated, heart worm disease can kill a dog. Death may occur within 72 hours. How they spread: Transmitted by over 70 species of mosquitoes. Virtually all dogs are at risk. Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice. BIOL 316 Phylum Platyhelminthes 28 Adult roundworms live in the dog's small intestine. What they do: Cause diarrhea, vomiting, stunted growth, rough coat, bloated belly. How they spread: Almost all puppies get roundworms from their mothers. Dogs can also pick up roundworms from the soil. Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice. BIOL 316 Phylum Platyhelminthes 29 Enlarged hook worm mouth showing 'teeth'. What they do: Attach to the dog's intestinal lining, leaving bleeding internal wounds. Cause blood loss, anemia, and diarrhea. As few as 100 hook worms can kill a puppy. How they spread: Eggs pass through the feces of an infected dog into the soil where they are easily swallowed or can penetrate through a dog's feet. Defending against them: Once a month prevention is recommended, contact your local veterinarian for advice. BIOL 316 Phylum Platyhelminthes 30 Symptoms: Larvae digested enter bloodstream and burrow into organs, causing absolutely horrendous pain and in some cases death. BIOL 316 Phylum Platyhelminthes 31 Filarial (threadlike worms) are nematodes that may block the passage of Fluids in the Body Disease: Elephantitis The disease is caused by parasitic worms, including Wuchereria bancrofti, Brugia malayi, and B. timori, all transmitted by mosquitoes. Lymphatic filariasis currently affects 120 million people worldwide, and 40 million Blocks Lymphatic nodes which drain fluid to and from the blood. Tropics, Africa and Asia BIOL 316 Phylum Platyhelminthes 32
