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PROTOSTOMES
2
Platyzoans—Phylum PlatyhelminthesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Ch
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Protostomes
Spiralia
EcdysozoaLophotrochozoaPlatyzoa
• Flatworms are ciliated, soft-bodied animals
• Bodies are solid aside from an incomplete digestive cavity
• Many species are parasitic
• Others are free-living
• Marine, freshwater, moist terrestrial
3
Flatworms
10 mm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Tom Adams/Visuals Unlimited
• Only one opening to digestive cavity
• Muscular contractions in the pharynx allows food to be ingested
and torn into small bits
• Lack circulatory system
• Diffusion for gas transport
• Gut functions in digestion and food distribution
• Some particles digested extracellularly
• Cells engulf particles by phagocytosis
• Tapeworms (parasitic flatworms) lack digestive systems –
absorb food directly through body walls
4
5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EyespotProtruding pharynx
Mouth
Testis
Oviduct
Sperm
duct
Circular
muscles
Longitudinal
muscles
Parenchymal
muscle
EpidermisNerve cord
Intestine
6
Reproductive
System
Excretory
System
Nervous
System
Intestine
Nerve
cord
Testis
Ovary
Anterior
cerebral
ganglion
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Have an excretory and osmoregulatory system
• Network of fine tubules runs through body
• Flame cells located on the side branches
• Flagella move water and excretory substances into the
tubules and then to pores located between the epidermal
cells through which the liquid is expelled
• Metabolic wastes are excreted into the gut and eliminated
through the mouth
7
• Simple nervous system
• Anterior cerebral ganglion and nerve cords
• Eyespot can distinguish light from dark
• Reproduction
• Most are hermaphroditic
• Undergo sexual reproduction
• Also have capacity for asexual regeneration
8
• 2 major groups of flatworms
• Free-living Turbellaria
• Probably not monophyletic
• Dugesia – common planarian in bio labs
• Parasitic Neodermata
• Trematoda – flukes
• Attach within host body by suckers, anchors, or hooks
• Life cycle may have 2 or more hosts
• Clonorchis sinensis, oriental liver fluke
• Cercomeromorpha – tapeworms
9
10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Metacercarial
cysts in fish
muscle
Metacercariae are
consumed by humans
or other mammals
Adult flukeMiracidium hatches after
being eaten by snail
Liver
Bile
duct
Egg containing
miracidium in feces
(into water)
Cercaria
Sporocyst
Redia
57 µm© Dwight R. Kuhn
• One of most important trematodes to human health are
blood flukes Schistosoma
• Afflict 5% of world’s population
• About 800,000 people die each year from schistosomiasis or
bilharzia
• Fertilized egg must break through the wall of the blood vessels
in intestine or the urinary bladder to get out
11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
125 µm
© The Natural History Museum/Alamy
• Cercomeromorpha – tapeworms
• Adult hangs onto inner wall of host intestine using scolex
12
500 µm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Dennis Kunkel/Phototake
• Most of tapeworm body is proglottids
• Complete hermaphroditic unit, containing both male and female reproductive
organs
• Formed continuously
• Beef tapeworm, Taenia saginata
• Frequent human parasite
• From eating uninspected rare beef 13
Scolex
Hooks
Sucker
Proglottids
Scolex attached
to intestinal wall
Uterus
Proglottid
Genital
pore
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LOPHOTROCHOZOANS—PHYLUM MOLLUSCA
• Second in diversity only to arthropods
• Include snails, slugs, clams, octopuses and others
• Some have a shell, some do not
14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Ch
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Protostomes
SpiraliaEcdysozoa
LophotrochozoaPlatyzoa
a. b.
c. d.
a.
15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Marty Snyderman/Visuals Unlimited; b: © Alex Kerstitch/Visuals Unlimited; c: © Douglas Faulkner/Photo Researchers, Inc.; d: © agefotostock/SuperStock
• Range in size from microscopic to huge
• Giant clams may weigh 270 kg
• Evolved in the oceans, and most groups have remained there
• Important source of human food
• Economically significant in other ways
• Pearls are produced in oysters
• Mother-of-pearl is produced in the shells of abalone
• Pests – Zebra mussel (Dreissena polymorpha)
16
MOLLUSK BODY PLAN
• Mantle
• Thick epidermal sheet
• Bounds mantle cavity
• Secrete shell (if there is one)
• Foot
• Primary means of locomotion for many
• Divided into arms or tentacles in cephalopods
17
• Internal organs
• Coelom is highly reduced
• Limited to small spaces around the excretory organs, heart,
and part of the intestine
• Digestive, excretory, and reproductive organs are concentrated
in a visceral mass
• Ctenidia – gills in aquatic mollusks
• Also filter food in most bivalves
18
19
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Radula
Gut
Lung
Foot
Gastropods
Shell
Antenna
Radula
Mantle
Gut
Shell
Gill Foot
Chitons
20
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Gut
Gill
Gut
Gill
Foot Mantle
Shell
Cephalopods
Bivalves
Siphons
Siphon
EyeArmMantle
cavity
Adductor
muscle
Tentacle
• Shell
• Protects against predators and adverse environments
• Secreted by outer surface of mantle
• Clearly not essential – repeated loss or reduction
• Typical shell has 2 layers of calcium carbonate
• Internal layer may be mother-of-pearl or nacre
• Pearls are formed by coating foreign object with nacre to
reduce irritation
21
• Radula
• Characteristic of most mollusks
• Rasping, tonguelike structure used in feeding
• Used to scrape up algae
• In predatory gastropods, modified to drill through clam shells
• In Conus snails, modifies into harpoon with venom gland
• Bivalves do not have a radula
• Gills used in filter feeding
22
23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Esophagus
Radula tooth
Muscles
MouthRadulaMouth
25 µmBottom: © Eye of Science/Photo Researchers, Inc.
• Nitrogenous waste removal – nephridia
• Consist of cilia-lined openings called nephrostomes
• Tube to excretory pore to mantle cavity
• Circulatory system
• Open circulatory system
• Hemolymph sloshes around hemocoel
• 3-chambered heart
• Cephalopods have a closed circulatory system
24
MOLLUSK REPRODUCTION
• Most mollusks are gonochoric
• A few are hermaphroditic
• Some oysters change sex
• Most engage in external fertilization
• Gastropods have internal fertilization
• Mollusk zygote undergoes spiral cleavage
25
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CLASSES OF MOLLUSKS
• There are 7 or 8 recognized classes
1. Polyplacophora – chitons
2. Gastropoda – limpets, snails, slugs
3. Bivalvia – clams, oysters, scallops
4. Cephalopoda – squids, octopuses, cuttlefishes, and chambered
nautilus
LOPHOTROCHOZOANS—NEMERTEA
• About 900 species of cylindrical to flattened very long
worms
27
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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ata
Ch
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Protostomes
SpiraliaEcdysozoa
LophotrochozoaPlatyzoa
• Most are marine; a few species live in fresh water and humid
terrestrial habitats
• Lineus longissimus has been reported to measure 60 m in length –
the longest animal known!
• Body plan resembles a flatworm
• Has a complete gut
• Rhynchocoel – fluid filled coleomic cavity
28
• Gonochoric with sexual reproduction
• Asexual reproduction through fragmentation
• Belong to lophotrochozoans because
• Blood flows entirely in vessels
• Rhynchocoel
29
30
LOPHOTROCHOZOA
NSPHYLUM
ANNELIDA
• Segmented worms
• Body built of repeated
units
• Allows for specialization
• May not be monophyletic
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Ech
ino
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Ch
ord
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Protostomes
SpiraliaEcdysozoa
LophotrochozoaPlatyzoa
• Body plan
• Head has well-developed cerebral ganglion
• Sensory organs in ringlike segments
• Many species have eyes
• Segments divided internally by septa
• Each segment has a pair of excretory organs, a ganglion,
and locomotory structure
• Closed circulatory system
• Ventral nerve cord
31
32
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Brain
Dorsal blood
vessel
Septa
Intestine
Nephridium
Mouth
Pharynx
Esophagus
Clitellum
Setae
Ventral blood
vessel
Nerve cord
Female gonads
Male gonads
Segments
Hearts
• Each part of digestive tract specialized for different
function
• Locomotion
• Coelomic fluid creates a hydrostatic skeleton
• Alternating muscle contractions allows complex movements
• Chaetae – bristles of chitin found in most groups
• Closed circulatory system
• Gas exchange by diffusion across body surfaces
• Excretory system – nephridia similar to mollusks
33
• Roughly 12,000 described species of annelids occur in many
habitats
• 2 classes
1. Class Polychaeta
• Monophyly not well established
2. Class Clitella
• Oligochaeta
• Hirudinea
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Protostomes
SpiraliaEcdysozoa
LophotrochozoaPlatyzoa
Phylum Nematoda
• Vinegar eels, eelworms, and other roundworms
• Members of this phylum are found everywhere – abundant and
diverse
• Marine, freshwater, parasites, free-living
36
181.1µm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Educational Images Ltd., Elmira, NY, USA. Used by Permission
• Bilaterally symmetrical and unsegmented
• Covered by a flexible, thick cuticle that is molted as they grow
• Digestive system well developed
• Stylets – piercing organs near mouth
• Pharynx – creates sucking action
• Anus
37
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Mouth
Dorsal nerve cord
Intestine
Testis
PharynxExcretory pore
Muscle
Pseudocoelom
Excretory duct
Intestine
Testis
Epidermis
Ventral nerve cord
Cuticle
Genital pore
AnusSpicules
• Sexual reproduction
• Most gonochoric
• Sexual dimorphism – male smaller with hooked end
• Internal fertilization
• Indirect development – egg, larva, adult
• Eutely
• Adults consist of a fixed number of cells
• Caenorhabditis elegans has only 959 cells
• Important in genetic and developmental studies
39
• Lifestyles
• Many are active hunters, preying on protists and other small
animals
• Others are parasites of plants
• Still others live within the bodies of larger animals
• Largest known nematode, which can attain a length of 9 m,
parasitizes the placenta of sperm whales
40
• About 50 species cause human diseases
• Hookworms
• Common in southern U.S.
• Produce anemia
• Trichinella causes trichinosis
• Forms cysts in muscles
• Infection from eating undercooked meat
41
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
50 µm© Gary D. Gaugler/Photo Researchers, Inc.
• Pinworms, Enterobius vermicularis
• Infects 30% of children in U.S.
• Causes itching of the anus
• Ascaris lumbricoides – intestinal roundworm
• Infects 1 in 6 worldwide
• Adult female can be 30 cm long
• Rare in areas with modern plumbing
• Serious tropical nematode diseases
• Filariasis
• Elephantiasis
42
ARTHROPODA
43
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Protostomes
SpiraliaEcdysozoa
LophotrochozoaPlatyzoa
• By far the most successful animals
• Well over 1,000,000 species (2/3 of all named species)
• Arthropods affect all aspects of human life
• Divided into four extant classes
• Chelicerata
• Crustacea
• Hexapoda
• Myriapoda
44
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3.4% Crustaceans
36.2%
Beetles
12.1%
Flies
12.1%
Butterflies,
moths
10.3%
Bees, wasps,
ants
8.6%
Other
insects12.1%
Other
arthropods
5.2% Arachnids
Arthropods are a successful group
About two-thirds of all named species
are arthropods. About 80% of all
arthropods are insects, and about half
of the named species of insects are
beetles
ARTHROPOD MORPHOLOGY
• Part of arthropod success explained by
1. Segmentation
• In some classes specialized into tagmata
• Head, thorax, abdomen
• Head and thorax may be fused into cephalothorax or
prosoma
2. Exoskeleton
• Made of chitin and protein
• Protects against water loss
• Must undergo ecdysis – molting
47
3. Jointed appendages
• May be modified into antennae, mouthparts, or wings
• Can be extended and retracted48
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Compound eye
Head
Thorax
Antenna
Mouth parts
Air sac
Malpighian
tubules
Abdomen
Rectum
Sting
Poison
sac
MidgutSpiracles
• Open circulatory system
• Nervous system
• Double chain of
segmented ganglia
• Ventral ganglia control
most activities
• Can eat, move, or
copulate with brain
removed
49
Head Thorax Abdomen
Spiracles
Tympanum
Compound
eye
Ocellus
Antennae
BrainAorta Stomach Ovary
Heart Rectum
MouthCrop Gastric
ceca
Malpighian
tubules
Nerve
ganglia
a.
b.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Compound eyes are found in many arthropods
• Composed of independent visual units called ommatidia
• Other arthropods have simple eyes, or ocelli
• May be in addition to compound eyes
• Have single lenses
• Distinguish light from darkness
50
51
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Ommatidium
Corneal lens
Crystalline
cone
Rhabdom
Retinular
cells
Pigment
cell
NervefiberOmmatidium
Optic nerve
Compound Eye
• Respiratory system
• Many marine arthropods have gills
• Some tiny arthropods lack any structure for gas exchange
• Terrestrial arthropods use tracheae
• Branch into tracheoles in direct contact with cells
• Connected to the exterior by spiracles
• Valves control water loss
• Many spiders use book lungs
• Leaflike plates
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Trachea
Spiracles
Tracheoles
Spiracles
• Excretory system
• In aquatic arthropods much of the waste diffuses out of gills
• Terrestrial insects and some others use Malpighian tubules
• Eliminates nitrogenous wastes as concentrated uric acid or
guanine
• Efficient conservation of water
54
BrainAorta Stomach Ovary
Heart Rectum
MouthCrop Gastric
ceca
Malpighian
tubules
Nerve
ganglia
b.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.