2 Phylum Arthropoda

Cards (125)

  • Arthropoda
    • Gk: arthrosjoints, podos – foot
  • Phylum Arthropoda - largest assemblage in the Animal Kingdom = 80% of all known species; 800,000 have been described; estimated total number of species is about 6 million
  • Characteristics of Phylum Arthropoda:
    1. Metamerism
    2. Exoskeleton
    3. Bilateral symmetry
    4. Paired jointed appendages
    5. Open & dorsal circulatory System
    6. Ventral nervous system
  • Metamerism – body is segmented, arranged into regions called tagmata (head, thorax, abdomen)
  • Exoskeletonchitinous covering (hard) that must be shed at intervals (ecdysis) or during growth (molting)
  • Hypothetical Evolution of Insect
    1. Segmented, legless, wormlike annelids
    2. Paired, bilateral, lobe-like appendages on the somite, with a pair of simple eye and antenna
    3. Bilateral appendages on each body segment becomes jointed, and with typical primitive mandibulate
    4. Differentiation of head, thorax and abdomen, with modified genitalia
  • Crustacea – e.g., lobsters, crabs, copepods
  • Crustacea - mostly aquatic gill-breathers
  • Crustacea - with 2 well-defined body regions: cephalothorax and abdomen
  • Crustacea - possess 2 pairs of cephalic appendages, antennae, and several pairs of branching appendages on remaining cephalothoracic segments, with few abdominal appendages
  • Crustacea - calcium salts impregnate the exoskeleton = rigidity
  • Arachnida – e.g., spiders, mites, ticks, scorpions
  • Arachnida - with 2 well-defined body regions: cephalothorax and abdomen
  • Arachnida - lack antennae with 6 pairs of appendages: 1 st pair – chelicerae (jawlike or fangs), 2nd pair – pedipalps (not leglike), remaining 4 pairs – legs
  • Myriapoda - with 2 body regions: head & trunk
  • Myriapoda - elongated, worm-like bodies, with 9 or more pairs of appendages
  • Diplopoda (milliepedes) - cylindrical or slightly flattened bodies
  • Diplopoda (millipedes) - with more than 30 pairs of legs, typically 2 pair of legs per body segment, and short antennae
  • Chilopoda (centipedes) - fewer legs than millipedes usually more than 15, with 1 pair per body segment
  • Insecta - contains the vast majority of medically important arthropods
  • Insecta - with 3 body regions (head, thorax and abdomen), 3 pairs of thoracic appendages, compound eyes and simple eyes (ocelli)
  • Phylum Arthropoda Members of Medical Importance:
    1. Crustacea
    2. Arachnida
    3. Myriapoda
    4. Insecta
  • Class Insecta: Integument/Exoskeleton
    • Body covering, made up of hardened/sclerotized plates (sclerites) separated by flexible ("membranous") regions, conjunctivae, or by grooves (sutures) = allows flexibility and protection
  • Class Insecta: Integument/Exoskeleton
    • Epidermissingle layer of cells that synthesizes and deposits the cuticle
  • Class Insecta: Integument/Exoskeleton
    • Dermal glandsinterspersed among the epidermal cells, secreting the outermost layer of cuticle including substances and various pheromones
  • Class Insecta: Integument/Exoskeleton
    • Apodemesinfoldings of the body wall (structural support) and attachment of muscle fibers
  • Class Insecta: Integument/Exoskeleton
    • Setaemulticellular, hairlike, one cell forming the projected portion (hair) and another cell forming the socket, pigmented and connected to a neuron and acting as sensory structures
  • Class Insecta: Integument/Exoskeleton
    • Spinesmulticellular, the cuticle of which is continuous with the integument
  • Class Insecta: Integument/Exoskeleton
    • Microtrichiasubcellular, tiny cuticular hairs that cover the cuticle
  • Class Insecta: General Insect Form
    • 3 regions: head, thorax & abdomen
  • Class Insecta: General Insect Form
    • Head – bears the mouthparts (ingestion) & sensory organs = a pair of compound eyes, simple eyes (dorsal ocelli), and a pair of antennae
  • Class Insecta: General Insect Form
    • Thorax (prothorax, mesothorax, & metathorax) – each thoracic segment bears pair of legs, when wings are present are borne on meso- and/or metathorax
  • Class Insecta: General Insect Form
    • Abdomen – composed of 11 segments: last segment is divided into a dorsal epiproct and lateroventral paraprocts and cerci/cercus, 8 and/or 9 segments bear the external genitalia
  • Class Insecta: Head
    • Head capsule – provides rigid points of attachment for mouthpart musculature
  • Class Insecta: Head
    • Cervixjoined the head capsule with the prothorax
  • Class Insecta: Head
    • Cervical scleritessmall plates in the cervix that provide articular points for both the posterior head capsule and the anterior edge of the prothorax
  • Class Insecta: Head
    • Foramen magnum – opening at the back of the head capsule where skeletal muscles, alimentary canal, aorta, and nerves enter
  • Class Insecta: Head
    • Frons - region between the compound eyes
  • Class Insecta: Head
    • Gena - lateral regions between the compound eyes
  • Class Insecta: Head
    • Vertex - located between the compound eyes at the dorsal of the head