The first bilaterally symmetrical coelomates Figure 33-1

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Chapter 33 PROTOSTOME ANIMALS

• The first bilaterally symmetrical coelomates

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Summary

• Why are protostomes important?
• General Characteristics
• Phylogeny
• Fossil record
• DNA analysis of rRNA
• Diversification
• Lophotrochozoans
• Ecdysozoans

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Figure 33-00
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Figure 33-2
Major protostome phyla
Major non-protostome phyla
Arthropoda
Chelicerates
Nematoda
Crustaceans
Myriapods
Insects
Mollusca
Platyhelminthes
Annelida
Ectoprocta
Chordata
Echinodermata
Cnidaria
Porifera
Other phyla
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Why Are We Interested in Protostome Animals?

• Food source crustaceans, mollusks
• Pollinate crops, enrich soil
• Eat crops
• Carry diseases, parasites
• Very diverse, very abundant
• Important in marine and terrestrial ecosystems.
• Research Drosophila C. elegans

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Figure 33-1
Fruit flies can be reared in bottles.
Caenorhabditis elegans is transparent and can be
reared in petri dishes.
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General Characteristics

• Embryonic development Protostomic, Triploblasty
• Bilateral symmetry
• Segmented bodies evolve in 2 groups
• Soft-bodied or exoskeletons of chitin or chitin
  CaCO3. i.e. Invertebrates

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General Characteristics

• Coelom ancester had a coelom however, some
  groups have reduced or lost the coelom, others
  have a pseudocoelom, fig 33.6

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Figure 33-6
Lophotrochozoa
Ecdysozoa
Platyhelminthes
Onychophora
Arthropoda
Tardigrada
Nematoda
Mollusca
Annelida
Rotifera
Deuterostomes
Acoelomorpha
No coelom
Reduced coelom
Pseudocoelom
Reduced coelom
Pseudocoelom
Coelom
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Phylogeny - Fossil Record

• Trilobites, extinct animals that existed 450-550
  mya. Segmented bodies, jointed appendages and a
  hard exoskeleton.
• Arthropods appeared about 520 mya
• Insects appeared about 400 mya around the time
  land plants proliferated.

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Phylogeny - DNA

• DNA analysis of rRNA produces 2 groups, fig 33.3
• Lophotrochozoa
• Ecdysozoa

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Figure 33-6
Lophotrochozoa
Ecdysozoa
Platyhelminthes
Onychophora
Arthropoda
Tardigrada
Nematoda
Mollusca
Annelida
Rotifera
Deuterostomes
Acoelomorpha
No coelom
Reduced coelom
Pseudocoelom
Reduced coelom
Pseudocoelom
Coelom
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Diversification

• Moved from water to land several times.
  Challenges were
• Various types of movement evolved
• Various eating structures evolved

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Lophotrochozoa

• Named for the feeding structure, lophophore, and
  larvae, trochophore, in some of the members, fig
  33.4.
• Grow by adding increments to their bodies.
• We will look at 4 of the 14 phyla Rotifera,
  Platyhelminthes, Annelida, and Mollusca.

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Figure 33-4
Lophophores function in suspension feeding in
adults.
Trochophore larvae swim and feed.
Food particles
Water current
Anus
Mouth
Mouth
Cilia used in locomotion and feeding
Anus
Gut
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Rotifera

• Free-living animals found in soil, marine and
  fresh water, fig 32.13

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Figure 33-12
Rotaria rotatoria
Corona
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Platyhelminthes - flatworms

• Parasitic and free-living varieties
• 3 classes Turbellaria, Trematoda and Cestoda,
  fig 33.13.

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Platyhelminthes

• Class Tuberllaria (planaria) free-living, feed
  on protists, small animals, dead animals.
  Reproduce by splitting in ½.
• Class Cestoda (tapeworms) endoparasites
• Attachment organ (scolex) with suckers and hooks.
  
• Eggs are produced, fertilized and develop into
  embryos in proglottids (sections). The sections
  break off and are excreted in feces of host.
  (Cattle and humans)

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Platyhelminthes

• Class Trematoda (flukes) endoparasites
• Life cycle involves 2 hosts - snail and
  vertebrate (fish and humans)
• Liver fluke (Clonorchis sinensis) and blood fluke
  (Schistosoma). (Snails and humans)

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Figure 33-13
Turbellarians are free living.
Cestodes are endoparasitic.
Trematodes are endoparasitic.
Taenia species
Pseudoceros ferrugineus
Dicrocoelium dendriticum
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Annelida segmented worms

• True coelom
• Series of segments are separated internally by
  septa.
• Closed circulatory system, beating blood
  vessels
• Digestive tract well-developed (pharynx,
  esophagus, crop, gizzard and intestine).
• Circular and longitudinal muscles for movement.

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Annelida 2 classes

• Class Polychaeta (bristle worms) many chaetae
• Some live in tubes, some are free swimmers or
  crawlers.

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Annelida 2 classes

• Class Clitellata -
• Mucous cocoon produced for fertilized eggs
  (clitellum).
• Hermaphroditic
• 2 groups
• Oligocheta (earthworms)
• Hirudinea (leeches)

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Figure 33-14
Most polychaetes are marine.
Most leeched live in freshwater.
Most oligochaetes are terrestrial.
Alvinella pompejana
Paranais litoralis
Hirudo medicinalis
Chaetae
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Mollusca

• Coelom reduced or absent
• Digestive, excretory and reproductive systems
  organized in visceral mass.
• Locomotion via muscular foot which is also used
  for attachment and food capture.
• Distinct head in some species

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Mollusca

• Mantle - membranous folds outer surface secretes
  a shell inner layer encloses visceral mass.
• Shell - protein covered, multiple layers of
  CaCO3 inside many produce mother-of-pearl.
• Visceral mass
• Gills
• Open circulatory system with a 3-chambered heart
  in most.
• Digestive system mouth, stomach, intestines,
  rectum and liver.
• Excretory system tubular structures called
  nephridia empty wastes into mantle cavity.
• Gonads

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Figure 33-7b
Mollusc body plan (internal view)
Gill
Muscular foot
Visceral mass (internal organs and external gill)
Mantle (secretes shell)
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Mollusca

• Muscualr foot
• Feeding
• Most have separate sexes, some are hermaphroditic
• External fertilization except gastropods

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Mollusca 4 classes

• Class Polyplacophora - Chitons have 8
  overlapping chitinous plates. Herbivores that
  graze along the floor of the ocean, fig 33.17.
• Class Gastropoda - Snails, slugs, nudibranchs.
  Mantle and anus moved toward mouth during
  development coiled shells or no shells.
  Herbivores and carnivores, aquatic and
  terrestrial, fig 33.16.

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Figure 33-17
Tonicella lineata
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Figure 33-16a
Snails have a single shell, which they use for
protection.
Maxacteon flammea
Land slugs and sea slugs (nudibranchs) lack
shells.
Chromodoris geminus
Bright colors warn potential predators of
presence of toxins
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Mollusca

• Class Bivalvia oysters, clams, scallops and
  mussels.
• 2 shells hinged together by a ligament. Mantle
  often secrete mother-of-pearl inside shells.
• Usually sessile (marine and fresh water), filter
  feeders.
• No distinct head but scallops have eyes along
  margin of mantle.

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Figure 33-15
Scallops live on the surface of the
substrate and suspension feed.
Lima scabra
Most clams burrow into soft subtrates and
suspension feed.
Water out
Food particles
Water in
Gill
Siphons
Gills are thin structures for gas exchange. They
also trap food particles as water passes through
them. Cilia move the particles to the mouth
Foot
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Mollusca

• Class Cephalopoda - octopuses, squids and
  nautiluses.
• Intelligent predators, foot has evolved into
  tentacles with suckers /or hooks. Beak-like jaw
  and a radula to capture prey

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Figure 33-10d
Jet propulsion
Cavity enclosed by mantle fills with water
Water is forced out through siphon animal moves
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Figure 33-18
Octopus dofleini
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Ecdyzoans

• Grow by molting shedding exoskeleton.
• Pseudocoeloms or reduced coeloms
• About 8 phyla 2 representative phyla are
  Nematoda and Arthropoda

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Nematoda - roundworms

• Pseudocoelom hydrostatic skeleton
• Includes marine fresh water varieties, soil
  varieties and parasites.

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Nematoda

• Sexual reproduction
• Includes hookworms, pinworms, Ascaris, etc.
• Diseases anemias, trinchinosis from pork and,
  filaria in lymph system (elephantiasis).

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Figure 33-21
Strongyloides species
Nematodes
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Arthropoda

• Development of jointed appendages and
  exoskeleton. Appendages include legs, antennae,
  mouthparts wings.
• Earths most successful animals
• Responsible for pollination of many crops
• Cause destruction of human food sources, and are
  carriers of diseases.
• Life cycle metamorphosis (2 types)

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Arthropoda

• Segmented body parts, usually fewer than
  annelids, some are fused.
• Distinct head
• Molting of exoskeleton
• Compound eyes, ommatidia, and simple eyes,
  ocelli.

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Arthropoda

• Open circulatory system, simple heart
• Nervous system brain ganglia
• Respiratory system
• Excretory system

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Figure 33-7a
Arthropod body plan (external view)
Tagma
Abdomen
Thorax
Head
Jointed limbs
Exoskeleton (covers body)
Segmented body
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Arthropoda S.P. Crustacea

• Crabs, shrimp, crayfish, lobster, barnacles, pill
  bugs, etc.
• Body has 2 regions, cephalothorax and abdomen
• 2 pair of antennae, 3 types of chewing appendages
  (biting mandibles), various numbers of legs.
• Gills or simple diffusion of gases
• Most have separate sexes, internal fertilization

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Figure 33-24
Deep-sea lobster
Red barnacle
Enoplometopus occidentalis
Tetraclita species
Barnacles secrete their own shells
Carapace
Fiddler crab
Uca vocans
Compound eyes on stalks
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Arthropoda S.P. Chelicerata

• Class Meristomata - horseshoe crabs.
• Class Arachnida - spiders, tarantulas, scorpions,
  mites and ticks.
• Terrestrial (silken webs) or marine
• Appendages paired fangs or pincers, paired
  pedipalps (used for copulation or develop into
  pincers), 4 pair of legs.
• Mostly carnivores, digestion before ingestion.
• Book lungs leaf-like plates for gas exchange,
  and tracheae.

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Figure 33-23
Spider, showing general chelicerate features
Mites are ectoparasitic.
Dolomedes fimbriatus
Dermatophagoides species
Posterior region
Anterior region
Chelicerae
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Arthropods S.P. Myriapoda

• Classes Chilopoda (centipedes) and Diplopoda
  (millipedes)
• Trachea for gas exchange Malpighian tubules for
  excretion of wastes.
• Head and numerous body segments, each with paired
  appendages, 1 pair/segment in centipedes and 2
  pair in millipedes.
• Internal fertilization, lay eggs
• Centipedes are carnivores, millipedes are
  herbivores.

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Figure 33-22
Scolopendra species
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Arthropoda S.P. Insecta

• Largest, most successful group
• Live everywhere, mostly terrestrial but some have
  invaded fresh and salt water.
• 3 body sections head, thorax, and abdomen. 3
  pair of legs on the thorax and 1 pair of antennae
• Compound and simple eyes

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Arthropoda S.P. Insecta

• 2 pair of wings, 1 pair may be modified, some
  have no wings
• Mouthparts 4 pair are modified for type of
  feeding.
• Larvae are wormlike (caterpillars)
• Movement swim, fly, walk or run.
• 10 major Orders of insects

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Figure 33-9
Leaf-cutter ants cut leaves.
Deer ticks pierce mammalian skin.
Nut weevils bore into hard fruit.
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Figure 33-23-Table 33-1-1
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Figure 33-23-Table 33-1-2