ARTHROPODS

• Arthropods

  • They are bilaterally symmetrical. Their bodies are divided into a number of rings or segments. They have jointed appendages, which may take the form of legs, antennae, or mouthparts.
  • They have a hard chitinous exoskeleton (cuticle).
  • The exoskeleton is partitioned by chitinous plates (sclerite).
  • They have a body cavity called haemocoel, which contains hemolymph (blood and lymph) .
  • Ecdysis or moulting is where the cuticle is shed at regular intervals in order to accommodate the growing tissues.
• Arthropods have a complete digestive system. They also have a

  circulatory system and a nervous system.
• Most arthropods have three body segments (segmata)

  1. Head
  2. Thorax
  3. Abdomen
• Sexual reproduction can be internal or external
• Life cycles of arthropods involve a series of structural changes known as metamorphoses, the actual sequence of which varies with different parasite groups
• Myriapoda - Millipedes, centipedes
• Crustacea - Crabs, lobsters, shrimps, barnacles, copepods, etc.
• Insecta - Beetles, ants, wasps, flies, mosquitoes, fleas, ticks, lice, mites, etc.
• Direct contact - direct contact with the pathogen, such as a needle prick or a cut.

  Mechanical transmission

  • Cyclo-propagative: The disease agent undergoes both developmental change and multiplies in number.
  • Cyclo-developmental: The disease agent undergoes only developmental change (no multiplication)
  • Transovarian transmission: The disease agent is passed onto the next generation through the eggs of the insect.
  • Transstadial transmission: The disease agent is passed from one stage of life cycle to another and then transmit the disease to man.
• Source of Nutrition:

  • Carbohydrates lipids, and protein that are important as a source of energy and for building body mass
• Feeding

  • Arthropods all have appendages and mouthparts (mandible) that help capture and eat prey carnivores, herbivores, detritus feeders, filter feeders, and parasites
• Arthropods do have complete digestive systems.

  • Fore gut deliver the food into the body,
  • Mid gut break up and digest the food
  • Hind gut move waste products out of the body
• The circulatory system of all arthropods is an as an open circulatory system
• Respiratory System

  • Gills or Branchiae - extract dissolved oxygen from water and to excrete carbon dioxide
  • Tracheal respiration - air moves through the openings of the body surface ( into special tubes ( extending into the body Tracheal respiration provides oxygen directly to the muscle tissues
  • Book Lungs - form of respiratory organ found in certain air breathing arachnid arthropods Each book lung consists of a series of thin plates that are highly vascular (i e richly supplied with blood) and are arranged in relation to each other like the pages of a book
• Arthropods are typically characterized as having a brain and a ventral nerve chord extending throughout the body.
• Excretory System

  • Terrestrial Arthropod

  –Malpighian tubules which are located on the body sinuses, they collect

  waste from the blood and concentrate them

  • Aquatic Arthropods

  –release their nitrogen containing waste through green glands These

  green glands are found near the bottom of the antennae
• Most arthropods are dioecious, but many are hermaphroditic, and some reproduce parthenogenetically
• Arthropods


  The largest phylum in the animal kingdom
• Main classes of arthropods

  • Crustacea
  • Chelicerata
  • Myriapoda
  • Hexapoda
• Crustacea


  • Typically have two pairs of antennae and branched appendages
  • Mostly aquatic, with a few terrestrial species
• Crustacea


  • Crabs
  • Lobsters
  • Shrimp
  • Barnacles
• Chelicerata


  • Characterized by the presence of chelicerae, which are specialized mouthparts
  • Lack antennae and have simple eyes
• Chelicerata


  • Spiders
  • Scorpions
  • Ticks
  • Mites
• Myriapoda


  • Possess many body segments, each with one or two pairs of legs
  • Terrestrial, with elongated bodies
• Myriapoda


  • Centipedes
  • Millipedes
• Hexapoda


  • Have three main body segments: head, thorax, and abdomen
  • Characterized by having six legs, one pair of antennae, and usually one or two pairs of wings
• Hexapoda includes insects, the most diverse group of arthropods