PHYLUM ARTHROPODA

PHYLUM ARTHROPODA
“joint” “footed” animals
Reticulitermes
Termite
Fortress
0.2 mm
Coconut Crab
hellgrammite
Dust
Mite
Spider Crab holding man
Zoologists Are Interested in Embryology
WHY?
Arthropods are “EUCOELOMATE PROTOSTOMES”
Deuterostomes
Protostomes
e.g.
Echinoderms
Vertebrates
e.g.
Molluscs
Annelids
Arthropods
Deuterostomes
Protostomes
e.g.
Echinoderms
Vertebrates
e.g.
Molluscs
Annelids
Arthropods
Arthropods exhibit metamerism
3 3P3
Phyla
insects
Origin (Chapter 9)
“if my theory be true, it is indisputable
that before the lowest Silurian stratum …
the world swarmed with living creatures.”
“Cambrian Explosion”
ARTHROPOD SUCCESS ….
WHY??
*
*
*
Insects
750,000 named species
30 million total ??
1 Reason for Success: the
Exoskeleton = Cuticle
- protective
- allows flexibility & mobility
- versatile
“Quads”
Mobility
Grasshopper
Hind leg
“Hamstrings”
human elbow
joint
Joint-Muscle
Similarity?
Arthropod Cuticle
Layered
Protein
Endocuticle
Layered
Glycoprotein
The “glyco” in glycoprotein: CHITIN
Chitin is a polysaccharide similar to cellulose: Light weight
Mechanically tough
Chemically inert
Unmodified Chitin: clear, flexible, resilient
Contrasting Cuticles
Contrasting Cuticles
Contrasting Cuticles
Cuticle Modifications for Toughening
e.g., Grasshopper thorax
Exocuticle becomes “tanned” or sclerotized (increased
cross-linking within & between glycoprotein layers)
e.g., Crab “shell”, lobster claw
Procuticle becomes impregnated with Ca++ salts
Cuticle Modifications for Waterproofing
Insect Problem: Dessication
- small size
- air is dessicating
- cuticles not water-tight
CUTICLE
WAX
GLAND
Solution???
Structure of a WAX
O
C
Fatty
Acid
O
CH2
CH2
CH2
CH2
(CH2)n
(CH2)n
CH2
CH2
CH3
CH3
Alcohol
Pillbugs are land crustaceans!!
NO WAX
Arthropod cuticles have 1 BIG drawback …
They don’t expand to allow growth!!!
Vertebrate
Bone Growth
RADICAL arthropod solution: the MOLT
http://www.youtube.com/watch?v=rDK3IT29uoQ
http://www.youtube.com/watch?v=2A1i10ZIB-w
Ecdysone
Secretes
Molting Fluid
(chitinase, proteases)
Molting Fluid attacks
Endocuticle
Old endocuticle
dissolved away
Phylum Arthropoda
Subphylum Myriapoda “many footed”
Class Chilopoda centipedes
-2 legs per segment (mostly)
-Predators (venom claws)
-Fast
Subphylum Myriapoda “many footed”
Class Diplopoda millipedes
-”1000 feet”
-Secretive & slow
-4 legs per segment (mostly)
-herbivorous
Subphylum Chelicerata
Class Arachnida
Order Araneae
http://video.nationalgeographic.com/video/kids/animals-pets-kids/bugskids/leafcutter-ant-kids/
Wolf Spider with egg sac
Phylum Arthropoda
Subphylum Hexapoda
Class Entognatha (springtails, snow fleas, etc.)
Class Insecta
“BUGS”
7,000,000,000 humans on earth …
for every person …
200,000,000 insects !!
We live in “The Age of Insects”
Surprise: not found in world’s largest habitat
Breath-taking diversity …
Master Niche Fillers
Friend and Foe
The Honeybee
BROWN MARMORATED
STINK BUG
Halyomorpha halys
Basic Body Plan
3 “Tagmata” (body regions)
Head
Thorax
Abdomen
Body
Variety
Body Plan
Variety
H
T
A
Earwig
Cerci
Defense
Prey Capture
Mouthpart
Variety
(sponges)
Sensory
Variety
Darwin saw usefulness
Vision
Leg
Variety
INSECT MOBILITY
All insect muscles are striated!
Muscles & Endoskeletons
(flexion)
Antagonistic Pairs
(extension)
Muscles & Exoskeletons
Antagonistic Pairs
Q: Which muscle
produces the leap?
1st in Flight???
Not Birds … Not Bats
Flight has huge implications
(foraging, reproduction, migration, escape, etc.)
24 - 26 Orders of insects …
22 have winged forms
Wingless orders in this group: silverfish, bristletails,
proturans, and springtails
2 Pairs of Wings
BEETLES
Forewings are protective
Hindwings for flight
“flies” – Order Diptera
2
Wings
Mud Dauber
collecting and…
transporting mud
Spiders packed
into a cell
larva
Mud Dauber
Nests
Adult Escape
Holes
Optimal Foraging?
Creationist WING Argument:
Only fully-formed wings could be beneficial
How did Darwin respond??
Weak Flying?
Gliding?
Thermoregulation?
Gas Exchange?
Behavioral Signal?
Communication
Function??
Sustainable Flight Speeds
Small grasshoppers
Malaria mosquitos
Housefly
Blowfly
Honeybee
Large dragonfly
Deer bot fly
1.8 km/hr
3.2
6.4
11.0
22.4
30.0
40.0 !!
Roughly Bolt’s
Top Speed
Forward Thrust
Downstroke
AND
Upstroke
FLIGHT MUSCLES
Direct & Indirect
Tergum
Indirect
Flight Muscle
Direct
Flight Muscle
Sternum
Bird-like
Bat-like
Note locations of fulcrum
and muscle insertion
Downstroke
Both Muscle
Groups are Indirect
Fulcrum … yes
Muscle insertion … no
http://www.youtube.com/watch?v=iUNRkvwIUQ0
Slow wing beats … slow neuromuscular activity
EXAMPLE: butterflies @ 4 beats/sec
Synchronous Neural Stimulation
1 action potential
1 set of muscle
cell contractions
NMJ
1 wing beat
Extreme wing speed …
Can nervous systems keep up??
Asynchronous Stimulation
e.g., some midges exceed 1000 beats/sec
midge
1000 beats/sec = 1 beat per ms !!
This should be IMPOSSIBLE … why?
Neuron refractory periods: 5 – 10 ms
In other words, muscles are contracting faster than nervous
systems operate !!
MECHANISM
When the upstroke muscles contract,
they stretch the downstroke muscles.
Downstroke muscles respond by contracting
which stretches the upstroke muscles.
This antagonism may continue several cycles
before a neural input is needed to keep it going.
In extreme cases, 40 wingbeats have been
recorded for each neural input.
FLIGHT TEMPERATURES
Thoracic temperature of a flying sphinx moth (Manduca sexta)
mammals
Flying and running are energetically
demanding … super lungs and heart??
NO (!)
(at first look)
Insect
Respiration
Spiracle
Body
wall
branching resembles that
inside mammalian lungs
Flying insects have large aerobic
requirements while having a crude
OPEN circulatory system.
PARADOX?
How do insects “get away with”
this system?
Danger of
Dessication
High SA:VOL exacerbated by …
flying ??
high metabolic rate?
producing urine?
H2O
Spiracles are Valved
Water Loss
In Urine
Hemolymph (blood)
in the
Hemocoel (body cavity)
[NO CAPILLARIES]
Marcello Malpighi (1628-1694)
NITROGENOUS Waste Products of Animals
Ammonia
Urea
Uric Acid
Cost of Synthesis
none
low
high
Toxicity
high
moderate
low
Solubility
high
high
Diffusion Coefficient
high
intermediate
low
1
2
4
N per osmotic particle
very low
Active in
re-claiming water
Hyperosmotic Urine (U/P> 1)
Significance??
What animals can produce it??
- Mammals
- Birds
Potent Kidneys
- Arthropods
(Malpighian Tubules)
Animal urine can be dilute … or concentrated relative to body fluids
U/P
osmotic pressure of urine
osmotic pressure of plasma
INSECT DEVELOPMENT
Holometabolous
Development
(88% of all insects)
Maggot
Grubs
Radical
reconstruction
HEMIMETABOLOUS DEVELOPMENT
A gradual metamorphosis
e.g., grasshoppers, cicadas, preying mantis, mayflies, dragonflies
Class Insecta
Order Coleoptera
Lepidoptera
Hymenoptera
Know examples
Diptera
from each Order
Hemiptera
Homoptera
Orthoptera
Friday’s Lab
Optimal Foraging by Butterflies
Natural selection pushes species TO BE ADAPTED to
their environment.
Useful traits often appear optimized.
Why not maximized??
Swimming in
cold water
Blubber: What is optimal for a seal?
optimal
Food to stomach?
Air to lungs?
Blood to brain?
Wouldn’t an even
longer neck be
better??
Trade-offs?
How long is
long enough?
OPTIMALITY MODEL
Benefit
Amount of
Cost or
Benefit
MAX
Opt
“Extent” of Phenotype
Cost
“proboscis”
Flow = ΔPπr4
8lη
P = pressure inside proboscis
r = proboscis radius
l = proboscis length
η = fluid viscosity
Lab Variable
Amount/mL
Amount/mL
?
Costs?
Concentration
SUGAR CONCENTRATIONS (%): 8.75, 17.5, 35, 50, & 80
(η)