Phylum Arthropoda 101

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Phylum Arthropoda 101

• 1. Bilateral Symmetry
• 2. Head, thorax abdomen (aka cephalothorax or
  prosoma) or just abdomen
• 3. Appendages with hinge joints (1pair/segment)
• segment somite
• 4. Exoskeleton
• 5. Open circulatory system
• 6. Respiration gills, tracheal tubes, booklungs
• 7. Brain, ventral nerve cord
• 8. Dioecious w/ metamorphosis and parthenogenesis
  (unfertilized egg develops)

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Habitats

• 35,000 ft deep in ocean 20,000 ft high in
  mountains
• Air, land, fresh water, salt water, parasitic
• Some are social, live in groups

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Size range

• Japanese crab 12 ft
• Under 1 mm in size

Japanese Spider Crab
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Evidence of Success

• Diversity in number of species
• All parts of the world
• Variety of habitats
• Variety of feeding habits

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Reasons for Success

• Exoskeleton protective, mobile
• Segmentation appendages better locomotion
• Tracheal system more oxygen gets to cells
• Sensory organs highly developed to capture
  food, evade enemies
• Complex behavior patterns/instincts survival
• Reduced competition for food larvae eat
  different food than adult form eats

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Subphyla Crustacea

• Crustacea 101
• antennae
• mandibles (chewing)
• maxillae (grasping)
• 1 pr appendages on each body segment
• Dorsal heart
• Ventral nerve cord
• Biramous 2 main branches on all appendages

MANDIBLES
MAXILLAE
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Class MalacostracaExamples Lobster, Shrimp, Crab
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External Features

• Covered with chitin, protein, and lime
• Cephalothorax (fused head/thorax)
• Carapace thickened area of exoskeleton over
  thorax
• Rostrum beak
• Pincer claws

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• 6. Uropod telson make up flipper
• Telson 1 middle of last abdominal segment
• Uropod 4 two on ea side of telson
• 7. Swimmerets under abdomen function in
  respiration, swimming, carrying eggs

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Internal Features

• Muscular system
• Flexor draws a body part toward body
• Extensor straighten out body part
• USE FLEXORS FOR SWIMMING BACKWARDS!!!

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Respiratory system

• Gills feather-like projections enclosed by
  carapace and attached to legs

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Circulatory system

• Open dorsal heart surrounded by pericardial
  sinus
• Blood (hemolymph) enters heart through ostia
  (openings) pumped through arteries
• Hemolymph colorless contains hemocyanin
  (copper containing respiratory protein) or
  hemoglobin
• Hemocoel blood cavity

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Excretory system

• Antennal glands (aka maxillary glands)
• A pair of tubular structures on the ventral part
  of the head
• OR
• Green glands
• spongy mass cleanse blood of cellular waste sent
  through excretory tubules to bladder to pore at
  exterior of animal

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Nervous system

• Brain with nerve to eyes antennae mouth double
  ventral nerve cord
• Pair of ganglia (bundle of nerves) for each
  somite (segment) nerves emerge from ganglia to
  go to each appendage, muscles, and organs

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Sense Organs

• Tactile hairs on antennae, mouth parts, telson
  function in taste and smell
• Statocyst located on first pair of antenna
  function in balance
• Compound eyes made up of units called ommatidia
  (each acting as a tiny eye see only shadows)

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Reproductive System

• Varies with species
• Most crustaceans dioecious
• Generally brood (care for) eggs by carrying eggs
  on abdominal appendanges
• Other arthropods, if males are scarce
  Parthenogenesis!
• Unisexual reproduction
• Production of young by females not fertilized by
  males
• Common in bees, ants, and wasps

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Ecydsis molting of exoskeleton

• Necessary for increase in size
• Exoskeleton is nonliving part
• Epidermis secretes exoskeleton (cuticle)
• Many layers deep
• Epicuticle outermost layer
• Exocuticle just beneath epicuticle
• Endocuticle principle layer thick membranous
• Procuticle innermost layer
• CONTROLLED BY HORMONES RELEASE OF HORMONES
  AFFECTED BY TEMPERATURE, DAY LENGTH, HUMIDITY

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Steps in formation

• 1. Procuticle separates from epidermis
• 2. Epidermis secretes new epicuticle
• 3. Epidermis secretes new exocuticle
• 4. Old epicuticle and exocuticle are discarded
• 5. New cuticle is stretched and folded and new
  endocuticle is secreted

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CLASS CHILOPODAExample Centipede

• General Characteristics
• Each somite contains one pair of jointed legs
  first pair are POISON CLAWS
• One pair of antennae one pair of mandibles 1-2
  pairs of maxillae
• Carnivorous feeds on earthworms, roaches,
  insects
• One pair of eyes

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CLASS DIPLOPODAExample Millipede

• General Characteristics
• Each somite contains two pair of legs
• Many simple eyes
• One pair of antennae, mandibles, maxillae
• Herbivores

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CLASS INSECTAExamples Flies, Butterflies, etc

• General Characteristics
• Most diverse and most abundant of all arthropods
• 1,000,000 species
• 3 pairs of legs, 2 pairs of wings

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Nutrition

• Phytophagous feed on plant juices
• Saprophagous feed on dead plants and animals
• Predaceous search and kill animals for food
• Parasitic feed on living organisms
• Hyperparasitism parasitic on parasites

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Respiration

• Tracheal system network of thin-walled tubes
  spiracles are openings to system

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Sense Organs

• Mechanoreceptor touch, pressure, vibration
  sensilla
• Auditory receptors sounds (w/ setae or
  tympanum)
• Chemoreceptors taste/smell
• Visual Reception simple or compound eyes

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Reproduction

• Fertilization is internal
• Pheromone hormone that acts as sex attractant
• Indirect Metamorphosis (aka holometabolous)
• egg larva pupae adult
• Direct Metamorphosis (aka hemimetabolous)
• egg nymph adult
• (NO PUPAL RESTING STAGE)

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• Diapause dormancy halted growth used to
  survive harsh conditions
• Hibernation winter rest
• Estivation summer inactivity

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Defense Mechanism

• Protective coloration camouflage
• Warning coloration red
• Mimicry color imitates another insect

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Communication

• Pheromones sex attractant, markers, alarm
  signals
• Sound crickets
• Tactile tapping
• Visual bioluminescence
• Dance bees

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Social Insects

• Bees
• Queen fertile female
• Drone male bee
• Worker infertile female

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Class Arachnida

• Arachnids spiders, scorpions, ticks, mites, and
  daddy longlegs (harvestmen)
• Mostly free living
• Most common in warm dry regions
• Most are predacious and have claws, fangs, poison
  glands, or stingers.
• Usually have strong sucking pharynx to ingest
  fluids and soft tissues from the bodies of their
  prey
• Interesting adaptation spinning glands

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Arachnid Anatomy

• Cephalothorax (fused head and thorax)
• Pair of chelicerae (chewing part with fang on
  end)
• Pair of pedipalps (used to manipulate food and
  sperm transfer)
• Four pairs of legs

1. egg case2. chelicerae3. pedipalps
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Arachnid Anatomy

• Abdomen (aka pedicel)
• Reproductive organs
• Respiratory organs (tracheae and book lungs)

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Arachnid Digestion

• Digestion
• release digestive enzymes over or into their
  prey then suck up the predigested liquid

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Dangerous Spiders in the US

• Black Widow
• Black shinky body with red/orange hourglass
  shape on abdomen
• Venom neurotoxic (affect nervous system)
• Bites can be fatal (general in small children or
  elderly individuals)

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FYI Black Widow Bite

• Renders no pain at the beginning
• Then it feels like damage by a small pin. As the
  below picture shows, two tiny red spots can be
  generally seen at the center point of the swollen
  area.
• But soon the venom spreads and the injury grows
  in size, reddeness, and dead tissue.
• It is very necessary that the victim attends to
  an emergency room in day number one also,
  succeeding in trapping the spider to show it to
  the doctor could be helpful at the time of
  prescribing the exact medication.

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FYI Territory of the Black Widow

• Black Widows are found in many areas of the
  United States, but they are most common in the
  South.
• This spider prefers a dark, damp habitat. It is
  most often found outside, but can be found inside
  in dark places inside dwellings such as sheds,
  garages, and closets.

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Dangerous Spiders in the US

• Brown Recluse
• Violin shape on cephalothorax
• Venom hemolytic (affect blood cells thus
  killing tissues)... death of tissues surrounding
  bite
• Bites are fatal to small children and older
  individuals

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Brown Recluse Bites Necrosis (localized death
of living tissue)
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Territory of the Brown Recluse