Phylum Arthropoda
Arthropods
“jointed foot”
“Arthro” = joint
“pod” = foot
Jointed legs
Arthropoda facts
• 750,000 species identified so far. More
than 3 times the number of all other
species.
• Include insects, crabs, centipedes and
spiders.
• They have a segmented body, a tough
exoskeleton and jointed appendages.
General Characteristics
• Segmented, bilateral
body
• Jointed appendages
• Exoskeleton
• Open circulatory
system
• Ventral nerve cord
• Compound eyes
The most successful animal!
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Number of species
Diversity
Distribution
Longevity
Reason for Success
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Versatile exoskeleton
Segmentation
Oxygen piped directly to cells (terrestrial)
Highly developed sensory organs
Complex behavior
Metamorphosis
Vocabulary
• Exoskeleton – a tough external covering
made of chitin.
• Chitin – a carbohydrate and protein.
• All arthropods have jointed appendages.
• Appendages – structures such as legs and
antennae that extend from the body wall.
Mayfly larvae
Form and Function in Arthropods
• They have specialized organs found only
in this phylum.
• They use tracheal tubes or other
specialized organs for respiration, have an
open circulatory system and excrete
wastes through saclike tubes.
Feeding
• Include herbivores, carnivores and
omnivores.
• They are bloodsuckers, filter feeders,
detritivores, and parasites.
• Many types of mouthparts: pincers, fangs,
and sickle-shaped jaws.
• Complete digestive system with two
openings
• Various mouthparts and structures that
aid in eating include chelicerae, fangs,
jaws, pedipalps, teeth, mandibles, etc.
Respiration
• Terrestrial arthropods obtain oxygen from
the air by branching tracheal tubes that
extend throughout the body. Air enters
and leaves through the spiracles. They
are small openings on the side of the
body.
• Spiders use book lungs. They are
respiratory organs stacked.
• Aquatic arthropods use featherlike gills.
Spiracles
Book Lungs
Circulation
• Arthropods have an open circulatory
system.
• They have a well developed heart which
pumps blood through arteries that go to
tissues. Blood leaves the tissues and
moves through the cavities. It collects in
the cavity around the heart where it is
pumped out again.
OPEN CIRCULATORY
SYSTEM
HEART with openings (OSTIA)
ARTERIES leaving heart but NO VEINS to
return hemolymph (blood)
Excretion
• Dispose of the nitrogen waste using
Malpighian tubes. They are saclike
organs that extract the waste from the
blood and add it to the feces.
• In aquatic arthropods, nitrogenous wastes
are removed by simple diffusion from the
body
Malpighian tubules
Response
• They have a well developed nervous
system. They have a brain and two
nerves that send incoming and outgoing
messages. They have sophisticated
sense organs and can see and taste
things very well.
Reproduction
• Terrestrial arthropods have internal
fertilization. Some species do have
external fertilization.
Movement, support, and body
plan
• Arthropods have an exoskeleton made of
protein, lipid, chitin, and calcium carbonate.
Chitin, a polysaccharide, is the major
component of the exoskeleton.
• Well-developed groups of muscles that flex
and extend to move appendages
• Arthropods will molt or shed their exoskeleton
to grow and develop.
• Coelomate
• Bilateral symmetry
• Segmented body (number of segments varies)
• Jointed appendages
Crayfish body plan
Growth and development
• When arthropods outgrow their
exoskeleton they must molt.
• The whole exoskeleton is molted.
• Skin glands digest the inner part of the old
exoskeleton and then it pulls it off.
p://www.baltimoresun.com/news/health/bal-cicadas-photos,1,7827762.special?coll=bal-spec
GROUPS OF ARTHROPODS
Characteristics to classify
arthropods
• Number and structure of their body
segments and appendages.
• Most focus on mouthparts.
Groups of Arthropods
• Subphylum Crustacea
• Subphylum Chelicerata
• Subphylum Uniramia
Crustaceans structures
• Two pairs of branched antennae.
• Mandibles – mouthparts
• Two or three body sections.
BODY PARTS
• Thorax – Section behind the head that houses
most of the internal organs.
• Cephalothorax – head fused to thorax.
• Abdomen – Posterior part of the body.
• Carapace – Part of the exoskeleton that covers
the cephalothorax.
• Mandible – mouth.
• Chelipeds – First pair of legs, usually bear
claws.
• Swimmerets – appendages used for swimming.
Chelicerates
• Include horseshoe crabs, spiders, ticks
and scorpions.
• They have four or five pairs of legs and
have mouthparts called chelicerae.
Death Stalker Scorpion
• A scorpion native to Northern Africa and
the Middle East.
It is a very aggressive type of scorpion.
• The sting is treatable, however if you do
not seek treatment after 48 hours most
stings are fatal to human.s
• Chelicerae – Contain fangs, which stab
and paralyze prey.
Pedipalps – Used to grab prey.
These events took place
in Australia.
A huge spider captured a
hapless bird which
became entangled in its
web - in a family's back
garden!
This is a Golden Orb
Weaver spider.
SPIDER BITES
Loxosceles reclusa
• Fiddle back spider
– Brown recluse
– Brown
– Violin
• Necrotoxin
51
Loxosceles reclusa
• Necrosis of tissue
52
Day 3
53
Day 4
54
Day 5
55
Day 6
56
Day 9
57
Day 10
58