1. Invertebrates: Phylum Porifera
Sponges
Multicellular; body a loose aggregate of cells
All aquatic, mostly marine
Body with pores (ostia), canals, and chambers for circulation of water
Epidermis of flat cells, some with contractile fibers
Middle layer is semi-fluid, with wandering amebocytes
Inner layer of choanocytes-flagellated to move water

2. Phylum Porifera cont’d
Filter feeders- intracellular digestion
Cells get food from circulating water
Classified based on skeleton
Composed of spicules
Chalk sponges - spicules of calcium carbonate
Glass sponges - spicules of silica
Proteinaceous sponges - spongin fibers
Reproduction
asexual by budding, sexual by fusion of gametes

3. Sponge
Fig. 30.3

4. Invertebrates: Phylum Cnidaria
Cnidarians
Multicellular, tubular or bell-shaped animals- radial symmetry
All aquatic, mostly marine
2 germ layers during development
Organized at tissue level
Nematocysts
stinging cells unique to cnidarians

5. Cnidarians cont’d 2 body types-polyps and medusae
Life cycle alternates between both forms in some; in others one form is reduced or absent
Gastrovascular cavity-sac-like body plan
Includes corals, jellyfish, and hydrozoans
Corals- polyps
Jellyfish-medusae
Hydrozoans-may have both forms

6. Cnidarian diversity
Fig. 30.4

7. Cnidarians cont’d Hydra Representative organism (Class Hydrozoa)
Freshwater, attaches to rocks, leaf litter
Small tubular polyp, sac-like body plan with a single opening
Outer tissue layer – epidermis from ectoderm
Inner layer – gastrodermis from endoderm
Longitudinal and circular muscle fibers present
Diffuse nerve net between layers

8. Cnidarians cont’d
Digestion begins in gastrovascular cavity, completed in cells
Can reproduce sexually and asexually (budding)
Sexual reproduction- hydra develops an ovary or testis in body wall-produces gametes

9. Anatomy of Hydra
Fig. 30.5

10. Invertebrates: Phylum Platyhelminthes
Flatworms
Bilateral symmetry, three germ layers, acoelomate
Mesoderm gives greater complexity
Muscles, excretory, reproductive, and digestive systems in some
Respiration by diffusion and circulation

11. Platyhelminthes cont’d
Class Turbellaria - Planarians
Free-living flatworms
freshwater, feed on small living and dead organisms
Ladder-like nervous system
Ganglia and eyespots anterior
Auricles – chemosensitive receptores
Digestion:
Feed through muscular pharynx
Specialized cells for excretion: flame cells

12. Platyhelminthes cont’d
Class Turbellaria - Planarians cont’d
3 muscle layers- circular, longitudinal, and diagonal
Allows for more complex movements
Cephalization
Organized to have an anterior end and a posterior end
Hermaphroditic

13. Planarian
Fig. 30.6

14. Parasitic Platyhelminthes
Class Cestoda (Tapeworms)
Internal parasites as adults
Body Structure
Tegument: tough outer covering
protect from host’s enzymes
Scolex - head
Barbs/hooks for attachment
Proglottids: segments
Each contains organs of both sexes
Lack a digestive system- why?

15. Parasitic Platyhelminthes cont’d
Class Cestoda (Tapeworms) (cont’d)
Reproduction
Fertilization is internal
proglottids filled with fertilized eggs are called gravid
Gravid proglottids drop off and pass out in feces
Ingested by intermediate host
larvae become encysted
Intermediate host is then eaten by definitive host
Larvae mature to adults
Representative Organism: Tanea solium
Pork tapeworm

16. Life cycle of a tapeworm, Taenia
Fig. 30.7

17. Parasitic Platyhelminthes cont’d
Class Trematoda - Flukes
Endoparasites of many species
Body Structure
Tegument
Oral sucker and posterior sucker
Digestion
Well-developed digestive canal

18. Parasitic Platyhelminthes cont’d
Class Trematoda - Flukes cont’d
Muscles and excretory system much like free- living flatworms
Poorly developed sense organs- why might that be?
Reproduction
Hermaphroditic
Complex life cycle involving two intermediate hosts

19. Parasitic Platyhelminthes cont’d
Class Trematoda - Flukes cont’d
Representative Organism: Clonorchis sinensis
Liver Fluke
Transmission
Snails ingest eggs
Develop in to larvae, which leave the snail and burrow into muscles of a fish
Humans ingest fish
Larvae moves into bile ducts where adults develop
Eggs pass out of human in feces, cycle continues

20. Invertebrates: Phylum Nematoda
Roundworms
First appearance of
Tube-within-a-tube body plan
2 openings, mouth and anus
Body Cavity
Pseudocoelomates
Pseudocoel -filled with fluid, acts as hydrostatic skeleton
Many species; some are free-living in soil and water, others are parasitic

21. Coelom structure and function
Fig. 30.8

22. Parasitic Nematodes Ascaris Move with whip-like motion
Intestinal parasites in many animal species
Females are much longer than males and highly prolific
Eggs enter host in uncooked vegetables, soil, or feces
Larvae burrow out of intestine and migrate to heart and lungs
Larvae are coughed up and swallowed
Mature to adults in intestines
Estimated to infect 25% of world population

23. Roundworm anatomy
Fig. 30.9

24. Parasitic Nematodes cont’d
Trichinella spiralis
the trichina worm
Causes trichinosis
Humans contract the worm by eating undercooked pork
Larvae migrate out of intestines and form painful cysts in the muscles

25. Parasitic Nematodes cont’d
Wuchereria bancrofti
filarial worm that causes elephantiasis
Migrates into lymphatic vessels and prevents lymph drainage
Edema occurs

26. Parasitic Nematodes cont’d
Pinworms and hookworms
Roundworm parasites which cause problems in children
Much more common in U.S.
Pinworms are primarily an annoyance
Hookworms cause skin irritations and in some cases debilitating disease