How does Cnidaria fit in? - PowerPoint PPT Presentation

Cnidaria

3 classes:Hydrozoa, Scyphozoa, Anthozoa

Porifera

2 body types: polyp, medusa

diploblastic

3 body types

tissue level

of organization

choanocytes

cellular level

of organization

Blastula stage

heterotrophic

multicellular

unknown

common ancestor

eukaryote

the acoelomates

Platyhelminthes

Nemertea

Cnidaria

Porifera

unknown

common ancestor

The Acoelomates

Organ level of organization

Tissues are organized to for organs which are used to accomplish physiological functions

Triploblastic

3 Tissue Layers

gastrodermis

mesoderm

epidermis

3 Embryonic Germ Layers

endoderm

mesoderm

ectoderm

No body cavity

ectoderm

ectoderm

mesoderm

mesoderm

Gut

endoderm

endoderm

Triploblastic

Mesoderm (mesenchyme, parenchyma)

Gut

Ectoderm

Endoderm

Bilateral Symmetry

Anterior: toward the front of the body

Posterior: toward the rear of the body

Cephalization

the concentration of sensory organs in the head of the animal

Eye spots

Auricles

Phylum Platyhelminthes

the flatworms

Feeding

• Free-living, carnivorous
• parasitic

Digestion

• intestine is simple or branched
• incomplete system (no anus)
• digestive system reduced or absent in parasitic species

Osmoregulation and excretion

• Protonephridia and flame cells
• much excretion is via diffusion

protonephridia

flame cell

Cerebral ganglia

Nervous system

-ladder-like

-cephalization

-nervous system is

reduced in parasitic

species

Lateral nerve cords

Skeletal and circulatory systems

• absent

Reproduction

Asexual

Sexual

• usually monoecious, but most must cross fertilize
• Internal fertilization (usually reciprocal)

Class Turbellaria

Class Trematoda

Class Cestoda

• Free-living flatworms
• move on slime trails using cilia

• predatory
• use a pharynx to capture prey

pharynx

• have a branched (or lobed) gut

Reproduction

Asexual

• Fission

Reproduction

Sexual

• internal fertilization
• simple life cycle

• increased reproductive potential
• monoecious
• presence of adhesion organs (suckers, hooks)
• poorly developed sensory systems
• reduced, or absent, digestive system
• resistant cuticle
• complex life cycles with more than 1 host

• Parasitic Flukes
• endoparasitic

• have at least two hosts in their life cycle
• final host = vertebrate

Vertebrate host #1

infective stage in host muscle

Vertebrate host #2

adult fluke

(in host liver)

Invertebrate

host eats eggs

Parasitic tapeworms

2 body regions: scolex and proglottids

scolex

proglottids

Scolex

suckers

rostellum

• Proglottids
• repeating segments containing reproductive organs
• may be immature, mature, or gravid

Immature proglottids

• found at the anterior end of the tapeworm
• contain no noticeable sex organs

Mature proglottids

• found in the middle of the tapeworm
• contain noticeable sex organs
• sperm must come from either a different proglottid or a different individual

genital pore

Mature proglottids

sperm duct

vagina

uterus

ovary

testes

Gravid proglottids

• found at the posterior end of the tapeworm
• contain fertilized eggs
• entire proglottid is shed in the host’s feces

uterus

eggs

Adult tapeworm

(in host intestine)

Gravid proglottids

Vertebrate host #2

Infective stage in host muscle

eggs

Vertebrate host #1

• Parasitic flatworms infect many people in some parts of the world (for example, the Chinese liver fluke infects approx. 30 million people in Asia)
• Some Trematodes have display polyembyony: a single larvae can have up to 4 younger larvae developing within it
• Trematodes are a model system for studying host parasite coevolution

Phylum Nemertea

the ribbonworms

Feeding

• Free-living, carnivorous
• have an eversible proboscis that is not connected to the digestive system
• Proboscis is used to stab prey and may have a poisonous tip (or stylet)

rhynchocoel

proboscis

mouth

rhynchocoel

Digestion

• intestine is unbranched
• complete system (mouth and anus)

This is the first animal to have an anus!!!

Reproduction

Asexual

• Some species are capable of reproducing asexually through fragmentation and regeneration

• Sexual
• usually dioecious
• internal fertilization

Osmoregulation and excretion

• same as Platyhelminthes

Nervous system

• same as Platyhelminthes

Skeletal system

same as Platyhelminthes

Circulation

• closed circulatory system consisting of contractile blood vessels

This is the first animal to have a closed circulatory system!!!

• Nemerteans are mostly marine, although there are a few species found in freshwater (and even a few on land!)
• They range in size from a few millimeters to 30 meters
• Their biology is little known in part because they are extremely fragile and fragment easily

Nemertea

Platyhelminthes

acoelomate

Complete digestive system

acoelomate

Closed circ. system

Ladder-like nervous system

Cnidaria

proboscis

Porifera

cephalization

protonephridia

organ level of organization

triploblastic

unknown

common ancestor