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

Pores• Ostia– 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

DemospongiaeLeuconoid

Forms

DemospongiaeLeuconoid 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