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Phylum Arthropoda :. Blueprint for Success Chapter 14 and 15. Characteristics of Arthropods. “Jointed foot” Modified segmentation – body regions specialized for specific functions ( tagmatization ). Chitinous exoskeleton used for support and protection Paired, jointed appendages

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phylum arthropoda

Phylum Arthropoda:

Blueprint for Success

Chapter 14 and 15

characteristics of arthropods
Characteristics of Arthropods
  • “Jointed foot”
  • Modified segmentation – body regions specialized for specific functions (tagmatization).
  • Chitinous exoskeleton used for support and protection
  • Paired, jointed appendages
  • Growth accompanied by molting (ecdysis)
characteristics of arthropods1
Characteristics of Arthropods
  • Ventral nervous system
  • True, but reduced coelom
  • Open circulatory system where blood is released into tissue spaces (hemocoel)
  • Complete digestive tract
  • Metamorphosis often present
  • Successful in almost all habitats on the earth.
  • Most abundant animals – Several million species identified
    • 30 to 50 million species may yet be undescribed
  • Triploblastic, protostome development
  • Exhibit bilateral symmetry
  • Four aspects contribute to arthropod success.
    • 1. Metamerism
    • 2. Exoskeleton
    • 3. The Hemocoel
    • 4. Metamorphosis
  • Segmentation, most evident externally
  • Each external segment bears a pair of appendages
  • Body cavity not divided internally
  • Permits the specialization of regions of the body for specific functions
  • Regional specialization = Tagmatization
    • Body regions (tagmata) specialized for: feeding, sensory perception, locomotion, visceral functions.
the exoskeleton
The Exoskeleton
  • External, jointed skeleton which encloses arthropods
  • Provides support, protection, and prevents water loss
  • System of levers for muscle attachment and movement
  • Secreted by epidermal cells
    • Epidermis covered by exoskeleton on outside
  • Consists of two layers:
    • 1. Epicuticle = outermost, waxy lipoprotein layer
    • 2. Procuticle/Endocuticle = bulky inner layer made of chitin
the exoskeleton1
The Exoskeleton
  • Hardening of the procuticle provides armor-like protection
  • Modifications of the exoskeleton
    • Formation of joints
    • Sensory receptors (bristles, lenses, etc)
    • Gas exchange
  • Must be periodically shed for growth (ecdysis)
the exoskeleton2
The Exoskeleton
  • Epicuticle and Procuticle:






the hemocoel
The Hemocoel
  • Provides an internal cavity for the open circulatory system of arthropods
  • Allows for the exchange of nutrients, wastes, and (sometimes) gases
  • Indirect development, a significant change in physiology as the immature form becomes an adult
  • Reduces competition between adults and immature stages
  • Evolution of arthropods has resulted in an increasing divergence of body forms, behaviors, and habitats between immature and adult stages.
    • Ex: Larval crabs feed on plankton, adult crabs prowl sandy bottoms for live prey.
    • Ex: Caterpillar feeds on leafy vegetables, adult butterfly feeds on nectar from flowers.
subphylum crustacea
Subphylum Crustacea
  • Examples:
    • Crayfish, crabs, lobster, shrimp, barnacles and copepods.
  • Two unique characteristics:
    • 1. Two pairs of antennae
    • 2. Biramous appendages
  • Five classes of crustaceans and numerous orders
    • Class Malacostraca**
    • Class Maxillopoda**
    • Class Branchiopoda
    • Class Remipedia
    • Class Cephalocarida
class malacostraca
Class Malacostraca
  • “Soft Shell”
  • Largest class of crustaceans:
    • crabs, lobsters, crayfish, shrimp, krill, isopods
  • Body divided into two regions
    • 1. Cephalothorax (fusion of sensory/feeding and locomotion tagmata)
    • 2. Abdomen (a muscular tail)
class malacostraca1
Class Malacostraca
  • Paired, biramous appendages in both body regions
  • Appendages on Cephalothorax:
    • Pairs 1 and 2 – Antennae (TWO pairs!)
    • Pairs 3 through 5 – Mouth appendages
      • Mandible Pair (Chewing)
      • Maxillae (Food handling)
    • Pairs 6 through 8 – Maxillipeds
      • Accessory sensory and food handling appendages
    • Pairs 9 through 13 – Pereopods (Walking legs)
      • Cheliped (Pincher-like: capturing prey)
  • Appendages on Abdomen
    • Pleopods (Swimmerets)
    • Telson used
class malacostraca3
Class Malacostraca


  • All crustaceans are dioecious
  • Mating occurs after molting of the female
  • In females, developing eggs attach to pleopods and are brooded until hatached
  • In males, pleopods are modified into claspers and used for sperm transfer
  • Crayfish have direct development
class malacostraca4
Class Malacostraca


Predators, herbivores, scavengers

Foregut includes an enlarged stomach, specialized for grinding

Midgut = “intestine”

Short hindgut ends in anus and used for water and salt regulation

class malacostraca5
Class Malacostraca

Gas Exchange & Circulation

Sensory & Regulation

Ventral nervous system

Compound eyes

Crayfish: Excretion organs are called “green glands”

Other crustaceans: maxillary glands

  • Gills in gill chamber
    • Between the carapace and body wall
  • Muscular Heart
  • Dorsal, anterior, and posterior arteries empty into sinuses of hemocoel
world s weirdest crustaceans
World’s Weirdest Crustaceans
class maxillopoda
Class Maxillopoda
  • Includes Barnacles and Copepods
  • Copepods are most abundant crustacean
    • Marine and Freshwater
  • Barnacles are sessile
    • Marine only
    • Most monoecious
    • Attach to various substrates
    • Some are parasitic
subphylum chelicerata
Subphylum Chelicerata
  • Class Arachnida
  • Spiders, scorpions, ticks, and mites
  • Eights Legs
  • No antennae or wings
  • Book lungs
  • Only two body segments
    • Cephalothorax
    • Abdomen

subphylum myriapoda
Subphylum Myriapoda
  • “Ten thousand foot”
  • Terrestrial
  • Contains millipedes and centipedes
  • Two body segments
    • Head
    • Trunk
subphylum hexapoda
Subphylum Hexapoda
  • “six foot”
  • Most successful land animals in terms of numbers of species and individuals
  • Bodies divided into three tagmata
  • Five pairs of head appendages
  • Three pairs of legs on thorax
world s weirdest insects
World’s Weirdest Insects
class insecta
Class Insecta
  • 30 Orders within Class Insecta!
  • Adult Generalized Insect Characterized by:
    • Body divided into head, thorax, abdomen
    • Three pairs of legs
    • Two pairs of wings
class insecta body plan
Class Insecta Body Plan
  • Head
    • Single pair of antennae
    • Mouthparts
    • Compound eyes
    • 0 to 3 ocelli (simple eyes)
  • Thorax
    • Three segments: prothorax, mesothorax, metathorax
    • One pair of legs attaches to each thoracic segment
    • Pair of wings attach at margin between mesothorax and metathorax
  • Abdomen
    • 10 to 11 abdominal segments
insect flight
Insect Flight
  • Insects utilize many forms of locomotion: walk, run, jump, swim, but flight is perhaps the most important
  • Insects were the first animals to fly
    • Important from an evolutionary perspective!
  • Wings most likely evolved from outgrowths of the thorax which protects the legs
  • Required thermoregulation
  • Some insects use a synchronous (direct) flight mechanism which others use an asynchronous (indirect) flight mechanism.
insect flight1
Insect Flight
  • Synchronous (Direct) Flight
    • Used by butterflies, dragonflies, and grasshoppers.
    • Flight muscles act on wing bases
    • A single nerve impulse in flight muscles results in a single wing cycle
  • Asynchronous (Indirect) Flight:
    • Used by flies and wasps
    • Flight muscles act on body wall
    • Changes in shape of the thorax cause wing movements.
    • A single nerve impulse results in many cycles of the wings
insect feeding
Insect Feeding
  • Variations in mouthparts include specializations for sucking or siphoning plant or animal fluids
  • Mouthparts:
    • Labrum- upper liplike structure, sensory and not derived from paired appendages
    • Mandibles- chewing mouthparts
    • Maxillae- have cutting surfaces and a sensory palp
    • Labium-sensory lower lip
    • All aid in food handling
insect digestive system
Insect Digestive System
  • Long and straight and consists of the foregut, midgut, and a hindgut.
  • Foregut
    • Behind pharynx is a crop that is used for storage
    • Proventriuculus or gizzard moves food to midgut helps grind
  • Midgut
    • Aids in digestion and absorption
    • Gastric cecae increase surface area
  • Hindgut
    • Primarily involved with reabsorption

of water

insect gas exchange
Insect Gas Exchange
  • Gas exchange with air requires a large surface area for the diffusion of gases
    • Accomplished through highly branched systems of chitin-lined tubes called tracheae
  • Tracheae open to outside of body through spiracles
    • Spiracles can close to prevent water loss
  • Most insects have ventilating mechanisms
    • Moves air into and out of tracheal system
    • Contracting flight muscles
    • Passive suction (vacuum) draws air in
    • Abdominal muscle contraction (pump)
insect circulation
Insect Circulation
  • Open circulatory system similar to other arthropods but blood vessels less well developed
  • Blood carries nutrients, hormones, wastes
  • Blood is not important in gas exchange
  • Most insects are ectotherms, but some generate heat using flight muscles
insect sensory functions
Insect Sensory Functions
  • Ganglion in head region
  • Sense organs specialized for functioning on land
  • Insects are capable of some learning have a memory
    • Bees recognize flowerlike objects
    • When bees are rewarded with nectar, they will choose flowers with that same odor in subsequent trials
  • Capable of detecting light
    • Used in orientation, navigation, feeding, etc
  • Compound eyes are well developed in adults