Kingdom Animalia Subkingdom Eumetazoa
Bilateria Phylum Arthropoda
Professor Andrea Garrison Biology 3A
Illustrations ©2014 Cengage Learning unless otherwise noted
Phylum Arthropoda
• Insects, spiders, crabs, millipedes, centipedes, etc. (arthron = joint; podos = foot)
• Largest animal phylum (>3/4 all species)
• All habitats • Triploblastic • Protostomes • Bilateral w/cephalization
– Sensory structures • Antennae, compound and/or
simple eyes, sensory hairs, auditory organs, statocysts
Ecdysozoa; photo http://www.cdc.gov/dpdx/trichinellosis/ 2
Hard Exoskeleton
• Chitin w/varying amounts of calcium carbonate
• Muscles attached to inside of exoskeleton
• Molt to grow – Develop soft exoskeleton under
the old exoskeleton – Shed old exoskeleton – Aquatic
• Swell with water, then exoskeleton hardens
– Terrestrial • Swell with air then exoskeleton
hardens
– Vulnerable to predators until new exoskeleton hardens
Arthropoda; photo by A. Garrison 3
Segmented Body
• External joints allow movement • Tagmosis
– Segments fused or grouped together in body regions • May be covered by carapace so you
don’t see segments (can count appendages)
– Segments within a region are similar
– Segments differ between regions
• 1 pair appendages/segment • Appendages may vary in
function – Feeding, defense, walking,
swimming
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Body Regions
• Head – Brain – Sensory structures
• Eyes (compound or simple) • Touch, chemical, hearing
– Feeding appendages
• Thorax – Walking or swimming
appendages – Some with wings
• Abdomen – May or may not have
appendages
Arthropoda; top photo by Didier Descouens; ,://creativecommons.org/licenses/by-sa/3.0/deed.en’ bottom photo by Fir0002/Flagstaffotos
5
Fir0002/Flagstaffotos
Body Regions
• Some body regions may be fused
– Cephalothorax • Head and thorax fused
– Abdomen
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Phylum Arthropoda
• Coelomate
• Complete digestive system – Head appendages
modified as mouthparts
• Open circulatory system – Hemocoel fills with
hemolymph
• 2 ventral nerve cords with ganglia – Attached to nerve ring
around mouth w/ “brain”
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Phylum Arthropoda
• Respiratory system – Aquatic
• Gills
– Terrestrial • Book lungs • Trachea
• Excretory system – Aquatic
• Paired glands at base of antennae
– Terrestrial • Malphigian tubules joined to gut
• Reproductive system – Dioecious – Internal fertilization – Several stages of development
between molts • Successive stages may be similar
or abruptly different
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Phylum Arthropoda
• 5 subphyla
– Trilobita
– Chelicerata
– Crustacea
– Myriapoda
– Hexapoda
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Subphylum Trilobita
• Trilobites (tri = three; lobos = lobe) • All extinct • Lots of fossils
– Arthropods first organisms with hard parts, molt several exoskeletons
• 3 lobes of body – 1 median lobe, 2 lateral lobes
• Dorsoventrally flattened • Heavy exoskeleton • 3 body regions
– Head • sensory antennae • compound eyes
– Thorax w/appendages – Abdomen w/appendages – Appendages on thorax and abdomen all
similar
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Subphylum Chelicerata
• Horseshoe crabs, spiders, scorpions, mites, ticks (chela = claw; keras = horn)
• Marine, freshwater, few terrestrial • Predators or parasites • Cephalothorax
– 6 pr appendages • 1 pr chelicerae—pincers to assist in
feeding • 1 pr pedipalps—grasping, sensory,
walking (pincers in scorpion to right) • 4 pr walking legs
• Abdomen – May have appendages
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Subphylum Chelicerata
• Class Merostomata – Horseshoe crabs – Very ancient, primitive group – Nocturnal feeder
• Worms, molluscs
– Compound and simple eyes – Carapace covers cephalothorax
• 1 pr chelicerae • 5 pr walking legs
– Abdomen • 6 pr swimming appendages • Book gills
– Telson
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Subphylum Chelicerata
• Class Arachnida – Spiders, scorpions, mites,
ticks
– Cephalothorax • Simple eyes may be image
forming
• 1 pr chelicera
• 1 pr pedipalps
• 4 pr walking legs
– Abdomen • No appendages
– Spinnerets exception to this
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Subphylum Chelicerata, Arachnida
• Spiders – Active hunters or spin webs to
capture prey • Spinnerets on abdomen • Liquid silk hardens on contact with
air
• Mites – Tiny – Cephalothorax and abdomen fused – Agricultural pests – Mange – Dust mites cause allergies
• Ticks – Blood-sucking ectoparasites – Cephalothorax and abdomen fused – Transmit bacterial pathogens
• Rocky Mountain spotted fever • Lyme disease
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Subphylum Crustacea
• Shrimps, lobsters, crabs (crusta = crust, hard shell)
• Marine, freshwater, very few terrestrial
• Most with cephalothorax and abdomen, but some with all three body regions
• Tagmosis well developed – Different regions with
different functions and different appendages related to function • Walking vs swimming
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Subphylum Crustacea
• Cephalothorax – Often covered by carapace
– 5 pr appendages on head • 2 pr antennae
• 3 pr mouthparts – 1 pr mandibles
» Bite, chew
– 2 pr maxillae
» Pass food to mouth
– More appendages on thorax and abdomen • Decapods
– 5 pr legs on thorax
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Subphylum Crustacea
• Well-developed nervous system – Large ganglia – Antennae with chemical
and touch receptors – Compound eyes – Statocysts on head – sensory hairs in
exoskeleton
• Respiration – Gills under carapace
• Excretion • Antennal gland
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Subphylum Myriapoda
• Centipedes and millipedes (myrias = ten thousand; pod- = feet)
• Terrestrial – Under rocks, leaves
• 2 body regions – Head
• 1 pr antennae
– Segmented trunk
• Centipedes – 1 pr walking legs/trunk segment – Predators
• Invertebrates and small vertebrates • Powerful toxins
• Millipedes – 2 pr walking legs/trunk segment – Feed on decaying leaves, organic
matter in soil
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Subphylum Hexapoda
• Insects (hex = six; pod- = feet)
• Most successful animal group – Every habitat
– Wings • Cross environmental
barriers, disperse
– Wingless groups • not as successful as
winged groups
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Subphylum Hexapoda
• 3 body regions – Head
• 1 pr compund eyes • 2-3 simple eyes (ocelli) • Mouthparts
– 1 pr antennae – 1 pr mandibles – 1 pr maxillae – 1 labium & 1 labrum cover
mouthparts – Mouthparts vary with feeding
style of insect
– Thorax • 3 pr legs • 2 pr wings in most
– Abdomen • No walking legs • Appendages for copulation
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Subphylum Hexapoda
• Respiration via tracheal system
– Spiracles open into system
– Tracheal tubes extend to tissues
• Excretion via Malphigian tubules
– Carry nitrogenous wastes to intestine to be released with feces
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Insect Development and Ecdysis
• Developmental stages beyond the egg called instars
• 3 types of development – No metamorphosis
• All instars look like mini-adults
– Incomplete metamorphosis • Only minor differences with each instar
• Early nymphs lack wings
– Complete metamorphosis • Drastic changes with each instar
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Insect Development and Ecdysis
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Insect Development and Ecdysis
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Insect Development and Ecdysis
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