Lab 37 Platyhelminthes and Nematoda

Transcription

1 Lab 37 Platyhelminthes and Nematoda - Bilateral symmetry - Protostome (mouth 1 st ) development - Mesoderm present - Two groups: lophotrochozoa and edcysozoa - Body cavity may be present or absent

2 Phylum Platyhelminthes: flatworms

3 Phylum Platyhelminthes: flatworms Flatten unsegemented body Gut with one opening (absent in tapeworms) Organ level of organization: nerve cords, protonephridia (excretory organs), and gastrovascular cavity Lack a Circulatory system and respiratory system Lack body cavity Beginning of a cephalization and light sensing organs

4 Class Turbellaria: free living flatworms Skin is ciliated Ventral opening to gastrovascular cavity with pharynx Aquatic predators

5 Sketch each of the following: Planaria (live) dissecting scope label eye spots, auricle Planaria slide (student slide) COMPOUND scope Label Eyespot, auricle, gastrovascular cavity, pharynx,

6 Class Cestoidea: tapeworms Skin is not ciliated Parasites of vertebrates, in the digestive system Lack a mouth and digestive tract Anterior end with hooks and suckers (scolex) Body has repeating units (proglottids) Proglottid used in reproduction and dispersal Beef tapeworm (25 m) Pork tapeworm (Cysticercosis)

7 Observe the specimen on the jar of a tapeworm Sketch each of the following Taenia (group slide) COMPOUND scope Sketch the scolex label hooks and sucker disc Sketch a proglottid

8 Class Trematoda: Flukes Leaf like body Skin is not ciliated Oral and ventral suckers Parasites of vertebrates Chinese Liver fluke, Sheep liver fluke Blood flukes How do people Get it? Schistosomiasis is the second most socioeconomically devastating parasitic disease after malaria

9 Observe the specimens of flukes in jars Sketch the following: Clonorchis, chinese liver fluke (student slide) label oral sucker, uterus, intestine, testes, mouth and pharynx

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11 Ecdyzoa group: Nematoda and Arthropoda They have a cuticle (non-living outer layer secreted by epidermis) Cuticle restricts growth and must be sheded via ecdysis Members of Ecdysozoa shed their cuticle as they grow Regulation of molting achieved by the hormone ecdysone

12 Phylum Nematoda: Roundworms - Cylindrical worms with unsegmented body - Body covered by a collagen cuticle (elastic but restricts growth), molted 4 times during growth - Body wall has only longitudinal muscles only - Found in virtually all habitats (poles, deserts, hot springs) - Handful of soil contains thousands of nematodes - Nematode parasites exist in nearly all animal and plant species

13 Free living roundworms In aquatic environments: they play a role in decomposition In soil environments: Predators of other nematodes and bacteria Important as food for mites, insects Vinegar eels Feed on bacteria and fungi found in nonpasteurized vinegar. They are raised by aquarists, who use them to feed newly hatched fish. C. elegans 1 mm long, living in soil environments

14 C. elegans as a model organism Multicellular and eukaryote, that is easily bred and can be frozen and thawed Entire genome sequenced Developmental fate of every cell determined Every neuron mapped It is proven useful in the study of cell death and Alzheimer's disease

15 Sketch : Live vinegar eel, compound microscope

16 Parasitic roudnworms In humans Hookworms: Pinworms: Most common worm parasite in the US but causes little disease

17 Parasitic roudnworms Ascaris lumbricoides is one of the largest and most common parasites found in humans. It is estimated that 25% of the world's population is infected with this nematode. In dogs and cats: Heartworms In Plants: Damage roots and transmit viruses (potato, soybean, grape vine)

18 Sketch one of the preserve specimens of Ascaris Sketch following: Ascaris cross section (student slide) FEMALE Cuticle, Pseudocoelome, uterus, muscles cells and intestine

19 End of chapter questions 2, 3, 5