Invertebrates: Phylum PoriferaSponges
Multicellular; body a loose aggregate of cells
All aquatic, mostly marineBody 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
30-1
Phylum Porifera cont’dFilter 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
30-2
Sponge
Fig. 30.3 30-3
Invertebrates: Phylum CnidariaCnidarians
◦Multicellular, tubular or bell-shaped animals-radial symmetry
◦All aquatic, mostly marine2 germ layers during
development◦Organized at tissue level
Nematocysts◦stinging cells unique to cnidarians
30-4
Cnidarians cont’d2 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
30-5
Cnidarian diversity
Fig. 30.4
30-6
Cnidarians cont’dHydra
◦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
30-7
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
30-8
Anatomy of Hydra
Fig. 30.5 30-9
Invertebrates: Phylum PlatyhelminthesFlatwormsBilateral symmetry, three germ
layers, acoelomateMesoderm gives greater
complexity◦Muscles, excretory, reproductive,
and digestive systems in some◦Respiration by diffusion and
circulation
30-10
Platyhelminthes cont’dClass 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
30-11
Platyhelminthes cont’dClass 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 30-12
Planarian
Fig. 30.6 30-13
Parasitic PlatyhelminthesClass 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?
30-14
Parasitic Platyhelminthes cont’dClass 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
30-15
Life cycle of a tapeworm, Taenia
Fig. 30.7 30-16
Parasitic Platyhelminthes cont’d
Class Trematoda - Flukes◦Endoparasites of many species
◦Body Structure Tegument Oral sucker and posterior sucker
◦Digestion Well-developed digestive canal
30-17
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
30-18
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
30-19
Invertebrates: Phylum NematodaRoundworms
◦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
30-20
Coelom structure and function
Fig. 30.8 30-21
Parasitic NematodesAscaris
◦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
30-22
Roundworm anatomy
Fig. 30.9 30-23
Parasitic Nematodes cont’dTrichinella 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
30-24
Parasitic Nematodes cont’d
Wuchereria bancrofti◦ filarial worm that
causes elephantiasis
◦ Migrates into lymphatic vessels and prevents lymph drainage
◦ Edema occurs
30-25
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
30-26
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