Non-Coelomate Animals
Porifera
• Simplest metazoan
• Cell level of organization
– Few cell types
– No true tissues
• Feed on material suspended in water
• Motile as larva - sessile as adult
• Ostia
Pores
– Small pores
– Water inlets
– Multiple ostia lead to canal system
• Osculum
– Large pores
– Water outlets
– Certain forms have more than one
Canal Structure
Four Types of Sponge Cells
Spicules
Hexactinellida – Glass Sponge
Demospongiae
Leuconoid
Forms
Demospongiae
Leuconoid Forms
Radiates
• Radial symmetry
• Tissue level organization
• Two germ layers
– Ectoderm and endoderm
• Nerve net (simple nervous system)
• Extracellular digestion
Radiate Phyla
• Cnidaria
• Ctenophore
Phylum Cnidaria
• Two forms
– Polyp
– Medusa
• Tentacles
• Nematocyst
Polyp and Medusa Forms
Hydra Tissue Structure
Obelia Life Cycle
Zoantharian
Coral
• Calcium carbonate
exoskeleton secreted
externally from base
• Contain mutualistic
zooxanthallae algae
• Live in colonies
• Hexamerous symmetry
Medusa
Hydra
Sea Anemone
Soft Corals
Coral Polyps
Phylum Ctenophora
• Comb Jellies
• Move using cilia
– Comb plates
• Do not have nematocysts
– Colloblasts capture food
Predatory Comb Jellies Approaching Prey
Predatory Comb Jelly Engulfing a Comb Jelly
Comb Jelly After a Meal
Acoelomate Phyla
• Platyhelminthes
– Flat worms
• Nemertea
– Ribbon worms
• Gnathostomulida
– Jaw worms
Why bilateral symmetry?
Movement toward prey or host
– Cephalization
– Directional sense organs
• Chemoreceptors
• Ocelli (light sensing eyespots)
• Rheoreceptors (sense water currents)
Acoelomates Key Features
• Three germ layers
– Ectoderm, endoderm, mesoderm
– Mesoderm forms muscle and mesenchyme
• Organ-system level of organization
– Cephalization
– Excretory system
– Some have circulatory and one-way alimentary
canal
Acoelomates Body Plan
Phylum Platyhelminthes
• Examples
– Planaria – freeliving
– Liver Flukes – endoparasite
– Tape Worms - endoparasite
Planaria
• Eye spots (Ocelli)
• Auricles - chemoreceptors
Liver Fluke – Digenetic Life Cycle
Liver Damage Caused By Flukes
• Scar tissue
• Blocked bile ducts
Tape Worm –
Digenetic Life Cycle
Tapeworm
• New proglottids are
added just behind the
scolex
Pseudocoelomates
• Pseudocoel
– Mesoderm muscle lined ectoderm
• Complete digestive tract
• Organs are within pseudocoel
Coelom
Phylum Nematoda
• Found everywhere
• Use pseudocoel as a hydrostatic skeleton
– Collagen cuticle
– Longitudinal muscles
• Free living and parasites
• Dioecious
Nematode Body Plan
Nematode Parasites
• Ascaris (roundworms)
– Found in intestine and lung.
• Hookworms
– Attach to intestine and suck blood.
• Trichina worm
– Forms cysts in muscle
– Causes trichinosis
• Pinworms
– Males are haploid, females diploid
– Live in large intestine
• Filarial worms
– Live in lymphatic system
Caenorhabditis elegans
• Extensively using in genetic and animal
development research
• Lineage of each cells is know and documented
• Whole genome is cloned and sequenced
Dirofilaria immitis
•
•
•
•
Dog and cat heart worm
Transmitted through mosquitoes
Most common in dogs
Infects heart and lungs
Brugia malayi
• Causes Elephantitis
• Swelling and blockage of
lymph ducts cause massive
swelling in late stages