Arthropoda

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Chapter 36

• Section 1
• Arthropoda

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Characteristics

• Lobsters, crabs, crayfish, spiders, insects
• Arthropods- members of the Phylum Arthropoda
• Segmented animals with appendages- such as legs
  antennae
• Arthropod means jointed foot

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Characteristics

• Exoskeleton- protection support
• 3 layers of exoskeleton
• Outer- waxy/protein- prevents water loss and
  drying out
• Middle- protection layer made of protein
  chitin- tough carbohydrate
• Inner-flexible/muscles-movement

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Characteristics

• Cephalization- brain/sensory structures located
  at anterior end
• Appendages around mouth to aid with feeding
• Antennae specialized for detecting chemicals

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Characteristics

• Open circulatory system
• Compound eyes- eyes made of many individual light
  detectors with lenses

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Molting

• Molting- shedding of the exoskeleton to grow
• Hormones trigger molting
• Arthropods usually hide during this stage because
  they are vulnerable to predators

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Evolution Classification

• Trilobites- ancient extinct arthropod
• Tagma- specialized for feeding, locomotion,
  reproduction
• Two major mouthparts mandibles- jaw-like
  chelicerae- pincer-like

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REVIEW!!!

• Name three characteristics of arthropods.
• Why do arthropods molt?

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Chapter 36

• Section 2
• Subphylum Crustacea

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Characteristics

• Two-pairs of antennae
• Mandibles
• Pill bugs, lobster, crayfish
• Nauplius- free-swimming larva stage

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Diversity of Crustaceans

• Range of sizes, but most are small
• Copepods- no larger than a comma ( , )
• Japanese spider crab- 13 feet

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Aquatic Crustaceans

• Copepods- marine (plankton)
• Water fleas (Daphnia)- freshwater
• Barnacles- marine- sessile attach to many
  different surfaces
• Cirri- appendages that sweep food particles into
  barnacles mouth

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Terrestrial Crustaceans

• Isopods- pill or potato bug
• Lose water quickly through thin exoskeleton
• Live in moist environments
• Roll into a ball when threatened as a defense
• Feed on decaying vegetation

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Crayfish

• Freshwater crustacean
• Similar to lobster
• Well-studied because of abundance
• Decapods- crayfish, lobster, crab, shrimp
  (10-feet)

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External Structure

• Body divided into abdomen cephalothorax-
  consists of head thorax- eight segments lies
  behind head
• Carapace- dorsal exoskeleton
• Abdomen- six segments behind cephalothorax

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External Structure

• Two pairs of antennae- touch taste
• Antennules- touch, taste, balance
• Mandibles- chew food
• Maxillae- manipulate food draw water over gills
• Maxillipeds- manipulate food

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External Structure

• Cheliped- capture food pincer defense
• Swimmeret- creating water current transferring
  sperm
• Telson uropods- paddle-like tail
• Move in backward movement called tail flip

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Digestion

• Esophagus ? stomach ? teeth-like structures in
  stomach grind food to fine paste ? mixed with
  enzymes secreted by digestive gland ? enters
  intestine for digestion absorption ? anus

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Respiration

• Feather-like gills for respiration
• As crayfish walk, circulate water over gills

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Circulation

• Open-circulatory system
• Circulatory fluid called hemolymph
• Exchanges carbon dioxide with oxygen in water
• Gills ? dorsal part of crayfish ? heart

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Excretion

• Green glands- excess water, along with wastes is
  eliminated
• Waste from green glands leaves through a pore at
  the base of the antennae

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Neural Control

• Ganglia
• Controls mandibles, maxillae, maxillipeds
• Ventral nerve cord runs from the ganglia into the
  thorax abdomen

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Sensory Organs

• Sense vibrations chemicals by sensory hairs
  over entire body
• Compound eye sense light

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REVIEW!!!

• Name three appendages of the crayfish and the
  function of each appendage.
• How do crayfish digest food?
• How do crayfish sense their environment?