Phylum Arthropoda
(The Arthropods)
•By far and away, the most successful animal group ever to live
•Consists of over 1 million named species, 2 of every 3 animals
are arthropods. ~ 1018 individuals.
–Inhabit all ecosystems
•General characteristics
•All have a hard exoskeleton
•Composed of protein and chitin
–Allows for great variation in function - biological "swiss army
knives"
–Must molt as they grow
–Limits their size
•Have well developed body segments and appendages
•Have well developed sensory organs including true eyes and
antennae
•Have open circulatory systems & special gas exchange organs
Could this be possible?
Subphylum Chilicerata
(arachnids, horseshoe crabs & sea spiders)
• Divided into 3 classes; Arachnida, Merostomata &
Pycnogonida
• Body divided into 2 regions
– Abdomen
– Cephalothorax (fused head & thorax)
• Lack jaws
• Have 6 appendages & no antennae
– First appendages form chilicerae (frequently fangs)
Class Arachnida
(Spiders, Scorpions, Ticks & Mites)
• Very diverse class
• Most species parasitic
or predatory
• Many possess book
lungs for gas exchange
• Spiders are able to
produce a strong
polymer - silk
• Chilicera in form of
fangs
Spiders
More Spiders…
Tarantula
Black Widow
For the true arachnophobe…
The brown recluse and its bite wounds
The Camel Spider
Ticks & Mites
Ticks & Lyme Disease…
Common Mites
Dust Mite
Common Mite
Scorpions
Class Picogonida
(Sea Spiders)
Class Merostomata
• Ancient group of
species
• Changed little over
350 million years
• Aquatic, mostly
found on Atlantic &
gulf coasts of
United States
Subphylum Uniramai
(3 Classes)
• Class Insecta (insects)
• Class Chilopoda (Centipedes)
• Class Diplopoda (Millipedes)
Class Insecta
(the insects)
• Far & away the most diverse of animal
groups
– More types of insects alone than all other
animal groups combined
– Inhabit all terrestrial & freshwater
ecosystems.
– Success largely attributed to coevolution
with flowering plants.
Insect Body Plan
•
•
Insects have 6 legs
3 body parts
– Head
– Thorax
– Abdomen
•
•
•
Most insects have wings, however in many species these are vestigal
Have advanced excretory system composed of malphygian tubules
Exchange gasses through a complex tracheal system
Vision
• Have complex compound eye which is usually
extremely sensitive to motion and allows 3600
vision
• Most insects see well into the UV spectrum
Feeding / Mouthparts
• Insects usually have
specialized
jaws/mouthparts
suited to their
ecological niche
Metamorphosis
• Most insects undergo a process of metamorphosis - 2
types
• Incomplete metamorphosis
– Larva similar to adult, with differing body proportions
– Undergoes a series of molts resulting in adult phenotype
Complete Metamorphosis
• Larva is very unlike adult phenotype
• Envelopes self in a coccoon or chrysalis where
body breaks-down and reforms into adult form.
Classes Chiopoda & Diplopoda
•
Millipedes (diplopoda) are segmented worm-like animals
– Have 2 pairs of legs per segment
– Primarily herbivores & decomposers
•
Centipedes (Chilopoda)
– Usually terrestrial carnivores
– Have 1 pair of antennae
– Are often poisonous, using modified front claws to immobilize prey
Centipedes vs. Millipedes
Centipede
Millipede
Subphylum Crustacea
• Includes crabs,
lobsters, crayfish,
shrimp, krill &
barnacles
• Over 40,000
species
• Appendages are
often highly
specialized
• Gas exchange is
usually through
gills
• Many species taste
delicious in butter
Some Crustaceans
Crayfish
Marine Maine Lobster
Crabs
Barnacles