Download Nematoda and Arthropoda

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Phylum Rotifera
•  Freshwater, freeliving (most), few
marine
•  Linked to Lophotrochozoa?
•  Many habitats and shapes
•  Many interstitial
•  Roto-feeders
•  Telescopic; semi-flexible
•  Protonephridia and diffusion
•  Reproduction: parthenogenesis
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General Body Plan
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Rotifer
Reproduction
• Most Dioecious
Ciliated Head= Corona
• Some parthenogenetic
Often a ringed cuticle to
allow for contraction (antenna)
Jawed Mastax for chewing
heavy-shelled
dormant egg, much
yolk; dormant egg
survives the winter
Flame cells and bladder
movie
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Nematoda- the roundworms
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Phylum Nematoda
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Basic Nematode body plan
•  Freeliving and parasitic
pseudocoelmates
•  Body structure:
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high SA:vol
Complete digestive tract
Separate sexes
Cuticle
•  C. elegans: an experimental
model
•  Parasites:
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Pseudocoel: high hydrostatic pressure
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Ascaris lumbricoides - The
Large Human Roundworm
•  1.5 Billon
infected
worldwide
•  200K eggs/
day
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Hook Worm: Necator americanus
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Fig. 15.7
Hookworm Lifecycle
800 million
people worldwide
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Trichinella spiralis-
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encyst in skeletal muscle
modify gene expression in cells
Pinworm: Enterobius vermicularis
Most common nematode parasite; 30% in children, 16% in adults- US
Scotch tape anyone?
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Guinea worms
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•  Copepod host
•  5cm/day- 3 weeks
rod of Asclepius
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Phylum Arthropoda: “jointed foot”
•  Evolutionary Origin: Analogous or homologous to
annelids?
•  Evolutionary Trends
1. Specialization of segments
2. Loss or fusion of body segments (tagmata)
3. Increased cephalization
•  Unique Arthropod Features
1. Jointed appendages- Legs!!
2. Exoskeleton
3. Reduced coelom
4. Ecdysis (molting) and hormonal control
5. Open circulatory system
6. Gills, book lungs or trachael tubes
7. Tracheal system
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Exoskeleton
•  Protective yet flexible, in many ways
•  Protein layers are bound with the
polysaccharide Chitin.
•  Lightweight, tough, flexible.
•  Can also have CaCO3
•  Stable and hard surface to attach muscle
–  Effective levers for efficient and fast motion.
•  Made into myriad tools.
•  But, limited by size…can’t get too big, at
least on land.
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Phylum Arthropoda: Segmentation,
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Specialization, and Diversification
Modern Arthropods: 4 main
evolutionary lines…a divergence into 4 variations on
a common theme.
•  Arthropod Subphyla:
–  Subph. Trilobitamorpha
–  Subph. Cheliceriformes
–  Subph. Crustacea
–  Subph. Hexapoda
–  Subph. Myriapoda
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Molting- Ecdysis
•  Problem- How grow in an
armored suit?
•  Well studied hormonal control
•  Re-absorption of old inner cuticle
•  New soft cuticle formed
•  Old “shell” left behind
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Subphylum Trilobita: extinct
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Extinct for over 200 my
2 cm to almost 1 meter in length
Segmentation with some fusion
Basic body plan: cephalon, thorax (3 lobes),
pygidium
•  Segmental specialization
but little specialization
in appendages
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Subph. Cheliceriformes : horse-shoe
crabs, sea spiders, spiders, ticks, scorpions
•  General Features:
–  2 major body segments
–  6 pairs of appendages w/
specializations
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Class Pycnogonida
Sea “Spiders”
Long, thin legs and body
Proboscis mouth for sucking
Male parental care of eggs and young
•  1 pair chelicerae (“fangs”)
•  1 pair sensory palps
•  4+ pairs of walking legs
•  3 Classes: Xiphosurida
Arachnida, and
Pycnogonida
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Class Arachnida: spiders, scorpions,
•  Adaptations to land
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Ticks and mites
Its not the mites that get you…
ticks, mites
Waxy cuticle
Gill replaced by book lungs
Appendage spec.
Malpighian tubules (also in insects)- metabolic wastes
Sensory specializations
Spinnerets: abdominal silk glands
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Subphylum Crustacea:
Mostly marine but some terrestrial members
Several Classes
Biramous Appendage
Requirements: exoskeleton
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Respiration
Circulation
Nitrogen wastes
sensory
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External
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Larval
Crustaceans
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Compound Eye
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Class Branchiopoda
Artemia, Brine shrimp
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Class Ostracoda
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Class MaxillopodaCopepods
• Mating displays
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Class MaxillopodaCirripedia- Barnacles
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•  Largest class of crustaceans
•  Most common orders:
Longest penis relative
to body height10X
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Class Malacostraca
–  Isopoda- dorsoventral flattened
–  Amphipoda- laterally flattened
–  Euphausia- krill
–  Decapoda- crabs and shrimp
–  Stomatopoda- mantis shrimp
Isopods
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Amphipods
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Amphipods
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Euphausia
Caprellid “shrimp”-amphipods
Decapods
• 2 body parts: fusion and
segmentation
• Cephalothorax: Head: 5 pairs of
appendages: antennae, mandibles,
maxillae. Thorax: 3+ pairs of
walking legs
• Abdomen: special appendages
for locomotion and reproduction.
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Order Stomatopoda
Mantis Shrimp
Phylum Arthropoda
video
• they have stereo vision
with just one eye;
• each eye is up on a stalk,
with a wide range of
motion;
• stomatopods have up to
16 visual pigments (in
contrast, we humans have
three—red, blue, and
yellow);
• stomatopods can see
ultra-violet and infra-red
light, and some can even
see polarized light.
•  Subph. Hexapoda
–  Insect success
•  Insect Body plan
•  Growth and Development
•  Social Behavior and
Communication
•  Subph. Myriapoda
–  Class Diplopoda
–  Class Chilopoda
Raskoff
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Subph. Myriapoda:
•  All terrestrial
–  Class Diplopoda- Millipedes
•  Up to 200 Seg.; two pair of legs/seg (fusion?)
•  Herbivores
–  Class Chilopoda- Centipedes
•  Up to 177 Segments; one pair of legs/seg
•  1st seg.= poison claws; Carnivorous
Subph. Hexapoda
Insect Diversity!- 1,000,000 + species
2 ancestral radiations
•  Flight: 245-360 mya
•  Angiosperm coevolution: 65-145 mya
•  Reasons for success?
–  1.Small size
–  2.Specialization reduces competition
–  3.Metamorphosis: intraspecific
specialization, reduced competition
–  4.Flight
•  Light skeleton
Fossils from late Jurassic (China)
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Insect Success: the Insect Body Plan
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3. Abdomen
–  Body plan adapted for terrestrial existence
–  3 segments
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•  1. Head: fused segments oriented downwards
Insect Body Plan cont’d:
Tracheal system w/ spiracles (also in spiders)
Malpighian tubules- nitrogenous wastes
Open circulation w/ tubular heart and hemolymph
Fused ventral nerve cords w/ ganglia
–  Sensory - 1 pair compound eyes, 2-3 pair simple eyes, 1 pair
antennae
–  Feeding - mandibles and maxillae
•  2. Thorax: locomotion - 3 pairs legs and wings
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Tracheal system
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Malpighian tubules
Nitrogenous waste removal
Diffusion and “body breathing”
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Muscle systems
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Primitive = Dragonfly like w/ non-folding wings
Folding of wings opened up vast new habitats…why?
Beat frequencies of 1000+ bps!
Nerve vs. myogenic impulse
Fulcrum/ seesaw analogy- small muscle movement=big
wing flap
•  Ability- Low to high; hover, dart. Fly is better than any
bird- hover, fly upside down, turn in 1 body length!
Fastest-25 mph. Very few gliders
How compare to your hand?
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Insect Flight
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Metamorphosis
Primitive and Advances Insects
Holometabolous
Monarch Butterfly
Danaus plexippus
•  Gradual Metamorphosis (Incomplete;
hemimetabolous): cockroaches, grasshoppers. Nymphs
or naiads (aquatic)
•  Complete Metamorphosis (holometabolous):
–  egg, larva, pupa (dormant form), adult
Adaptive
significance of
larvae?
9/26 orders are
holo, but = 88%
of species!
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