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General Body Plan. Diploblastic epidermis gastrodermis Tissue Radially symmetrical Cnidocytes. General Body Plan. Dimorphism: 2 different body forms are usually present in the life cycle:. aboral. oral. aboral. oral. 3 Classes. Hydrozoa: polyp dominant Scyphozoa: medussa dominant

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general body plan
General Body Plan
  • Diploblastic
    • epidermis
    • gastrodermis
  • Tissue
  • Radially symmetrical
  • Cnidocytes
slide2

General Body Plan

Dimorphism: 2 different body forms are usually present in the life cycle:

aboral

oral

aboral

oral

slide3

3 Classes

  • Hydrozoa: polyp dominant
  • Scyphozoa: medussa dominant
  • Anthozoa: no medussa
the acoelomates

The Acoelomates

  • Trploblastic animals without a coelom
acoelomate characteristics triploblastic
Acoelomate Characteristics: Triploblastic

3 Tissue Layers

gastrodermis

mesoderm/

mesenchyme

epidermis

3 Embryonic Germ Layers

endoderm

mesoderm

ectoderm

slide6

zygote

blastocoel

archenteron

blastopore

ectoderm

endooderm

mesoderm

acoelomate characteristics no coelom
Acoelomate Characteristics: No coelom

What is a coelom?

A body cavity that is completely surrounded by mesodermal tissue. A coelom is not open to the outside of the animal.

acoelomate characteristics no coelom1
Acoelomate Characteristics: No coelom

gut

gut

endoderm

endoderm

gut

acoleomate characteristics level of organization
Acoleomate Characteristics:Level of Organization

Organ

  • Tissues are organized into organs
  • mesodermal tissue gives rise to many organs
acoleomate characteristics body plan
Acoleomate Characteristics:Body Plan

Bilateral Symmetry

Anterior: toward the front of the body

Posterior: toward the rear of the body

slide13

Acoleomate Characteristics:Body Plan

left

anterior

dorsal

right

posterior

ventral

body plan
Body Plan

Cephalization: the concentration of sensory organs in the head of the animal

Eye spots: photosensitive organs

Auricles: chemoseneory organs

slide15

Acoelomate Phyla

1. Gnathostomulida

2. Platyhelminthes

3. Nemaertea

slide17

Phylum Platyhelminthes:

  • Mostly aquatic, although there are a few terrestrial species.
  • Most are small (a few mm), but some can grow to be sever meters long.
  • Many are endoparasites of vertebrates.
feeding and digestion
Feeding and Digestion

Feeding

  • Free-living, carnivorous

Many predatory forms have a pharynx that is used to capture prey

feeding and digestion1
Feeding and Digestion

Pharynx: the pharynx is an extension of the gut that can be extruded though the mouth.

feeding and digestion2
Feeding and Digestion

Feeding

  • parasitic

Parasitic forms often have modified feeding structures (e.g. the anterior end of a tapeworm)

hooks

suckers

feeding and digestion3
Feeding and Digestion

Digestion

  • incomplete digestive system

mouth

gut: saclike

pharynx

pharyngeal opening

feeding and digestion4
Feeding and Digestion

Digestion

  • many forms have a branched gut

The trilobed gut of a planarian.

feeding and digestion5
Feeding and Digestion

Digestion

  • the digestive system is reduced (or absent) in many parasitic forms
feeding and digestion6
Feeding and Digestion

intestine

Taenia pisiformis

intestinal parasite

NO DIGESTIVE SYSTEM !

Bdelloura candida

Free-living:branched gut

Grylodactylus

liver fluke: relatively unbranched gut

feeding and digestion7
Feeding and Digestion

Digestion

  • extracellular (in the intestine)
    • proteolytic enzymes released by gastroodermal tissues
  • intracellular
    • phagocytosis by gastrodermal cells
osmoregulation and excretion
Osmoregulation and Excretion

Osmoregulation: the maintenance of salt/water balance

  • Protonephridia and flame cells
osmoregulation and excretion1
Osmoregulation and Excretion

Protonephridia

Protonephridia: a system of tubules used to collect fluid and transport it to the outside of the body

osmoregulation and excretion2
Osmoregulation and Excretion

The beating of the flame cell cilia creates negative pressure which pulls fluid out of the body

protonephridia

flame cell

osmoregulation and excretion3
Osmoregulation and Excretion

Excretion

  • Diffusion of waste
nervous system
Nervous System

The Cnidarian nerve net:

receptor

neuron

nervous system1
Nervous System

Platyhelminthes have a more complex nervous system

Cerebral ganglia

Lateral nerve cords

Transverse nerves

nervous system2
Nervous System

pigment cup

retinular cells

light sensitive region

support and locomotion
Support and Locomotion

Skeletal System

  • No skeletal system
locomotion
Locomotion

Many small flatworms crawl on “slime trails” using cilia.

locomotion1
Locomotion

cilia on the dorsal epidermis

rhabdites: produce mucus

locomotion2
Locomotion

Large species use circular and longitudinal muscles to swim.

locomotion3
Locomotion

circular muscles

longitudinal muscles

reproduction
Reproduction

Asexual: fission

many flatworms are capable of reproducing asexually by constricting their bodies and separating into two individuals

reproduction1
Reproduction

Asexual

Periods of asexual reproduction are common in many parasites.

reproduction2
Reproduction

Sexual

  • usually monoecious, but most must cross fertilize
  • Internal fertilization (usually reciprocal sperm transfer)
phylum platyhelminthes1
Phylum Platyhelminthes

Class Turbellaria

Class Trematoda

Class Cestoda

parasitic

class turbellaria
Class Turbellaria

Free-living flatworms

slide43

Body Plan

cerebral ganglion

eye spot

anterior branch of intestine

ovaries

nerve cords

pharynx

testes

posterior branches of intestine

digestive system1
Digestive System

triclad

polyclad

reproduction3
Reproduction

Asexual: fission

many flatworms are capable of reproducing asexually by constricting their bodies and separating into two individuals

reproduction4
Reproduction

Sexual

  • Internal fertilization
  • Simple life cycle
phylum platyhelminthes2
Phylum Platyhelminthes

Class Turbellaria

Class Trematoda

Class Cestoda

parasitic

adaptations for parasitism
Adaptations for Parasitism

Increased reproductive potential

The presence of adhesion organs

Poorly developed sensory systems

Reduced or absent digestive system

Resistant cuticle

Complex life cycles

class trematoda
Class Trematoda

Parasitic Flukes

Endoparasites of many animals

slide51

Body Plan

oral sucker and mouth

intestine

ventral sucker

reproductive organs

complex life cycle
Complex Life Cycle

Most Trematodes have at least two hosts in their life cycle: e.g. the Chinese liver fluke

  • Clonorchis:
  • Found throughout Asia
  • Infects 30 million people
  • 1 fluke can produce 4000 eggs/day and live for > 8 years
complex life cycles another example
Complex life cycles: another example
  • Schistostoma:
  • Found throughout Africa and South America
  • Infects 200 million people
slide54

oral suckers

female

gynecophoric canal

male

slide55

The creation of the Aswan Dam led to an epidemic of schistosomiasis.

About 50 % of Egyptians living near the dam are now infected.

body plan1
Body Plan

2 body regions: scolex and proglottids

scolex

proglottids

body plan tegument
Body Plan: tegument

glycocalyx

Microtriches: increase SA:V

And nutrient absorption

Syncitial epidermis: no cell membranes

circular muscles

longitudinal muscles

nucleus

body plan2
Body Plan

Scolex

suckers

rostellum

body plan3
Body Plan

Proglottids

repeating segments containing reproductive organs

May be immature, mature, or gravid

class cestoda1
Class Cestoda

Immature proglottids

Immature proglottids are found at the anterior end of the tapeworm and contain no noticeable sex organs

class cestoda2
Class Cestoda

Mature proglottids

Mature proglottids are found in the middle of the tapeworm and contain noticeable sex organs

class cestoda3
Class Cestoda

Female organs

yolk gland

ovary

seminal receptacle

genital pore

vagina

uterus

class cestoda4
Class Cestoda

Male organs

genital pore

seminal vesicle

sperm duct

testes

class cestoda5
Class Cestoda
  • Individuals are monoecious, Reproduction is sexual
    • between proglottids on 1 individual
    • between individuals
    • Sperm do not usually fertilize eggs produced within the same proglottid
class cestoda6
Class Cestoda

Gravid proglottids

Gravid proglottids are found at the posterior end of the tapeworm and are shed in the feces.

A single proglottid can contain thousands of eggs.

cestoda life cycle
Cestoda Life Cycle

Adult tapeworm (in host intestine)

Gravid proglottids

Vertebrate host #2

Infective stage in host muscle

eggs

Vertebrate host #1

slide68

+

-

Predation

Herbivory

Parasitism

Disease

Mutualism

+

Predation

Herbivory

Parasitism

Disease

Competition

-

how are parasites and disease different from predators
How are parasites and disease different from predators?
  • Predators kill their prey, but hosts are usually not killed by parasites. Parasites affect hosts in more subtle ways.
  • Some examples of non lethal effects of trematode parasites on their hosts.
trematodes and host behavior

Infected population

Uninfected population

Trematodes and Host Behavior

Fundulus parvipinnis

Euhaplorchis califoniensis

Lafferty and Morris 1996

trematodes and host morphology
Trematodes and Host Morphology

Limb deformities in amphibians have been recorded since the 1950’s.

Since the early 1990s, there has been an apparent increase in the number of frogs found with limb deformities.

Several hypotheses have been proposed to explain these: Pesticides, UV, parasites…

slide75

Deformities

Survival

Deformities

Survival

Johnson, et al. 1999

slide77

There might be more to the story than just parasites:

  • Deformities are more common near agricultural run-off.

Agricultural run-off

No run-off

From Kiesecker 2002

slide78

There might be more to the story than just parasites:

  • Pesticides affect a frog’s immune response to the parasite.

From Kiesecker 2002

slide79

There might be more to the story than just parasites:

  • Trematodes do not induce this type of deformity.
slide80

References:

Kiesecker, J. M. 2002. Synegism between trematode infection and pesticide exposure: a link to amphibian limb deformities in nature. PNAS 99(15): 9900-9904.

Johnson, P.T.J., et al. 1999. The effect of trematode infection on amphibian limb development and survivorship. Science 284: 802- 804.

phylum nemertea

Phylum Nemertea

the ribbonworms

physiology
Physiology

Feeding

  • Free-living, carnivorous
  • Have an eversible proboscis that is not connected to the digestive system
physiology1
Physiology

rhynchocoel

proboscis

mouth

anus

rhynchocoel

physiology2
Physiology

Digestion

  • extracellular (in the intestine)
  • intracellular (by gastrodermal cells)
  • intestine is unbranched
  • complete system (mouth and anus)
physiology3
Physiology

Reproduction

Asexual

  • Some species are capable of reproducing asexually through fragmentation and regeneration
physiology4
Physiology

Reproduction

Sexual

  • usually dioecious
  • Internal fertilization