Ch 14: Phylum Arthropoda

1
Ch 14 Phylum Arthropoda
2
General Features

• Metamerism - body composed of a series of similar
  segments each bearing a pair of appendages
• Tagmatization - body regions are specialized for
  feeding, sensory perception, locomotion
  visceral functions
• Exoskeleton made of chitin provides support
  protection
• Paired, jointed appendages

3
More features of Phylum Arthropoda

• Growth accompanied by molting or ecdysis
• Ventral nervous system with highly developed
  sense organs
• Open circulatory system
• Complete digestive tract
• Metamorphosis present - this reduces competition
  between immature adult stages

4
What purposes do Arthropods serve?

• Food such as lobsters, crabs, shrimp
• Pests that damage crops
• Pollinators of flowers crops
• Vectors of diseases - for example, they carry the
  parasites for Malaria, Lyme disease African
  sleeping sickness, Bubonic Plague, Typhus, Yellow
  Fever, Encephalitis

5
Subphylum Trilobitomorpha

• Trilobites became extinct 200 million years ago
• Oval, flattened, 3- lobed body
• Head had antennae eyes trunk had appendages
• Can roll its body into a protective ball
• Bottom dwelling scavengers

6
Subphylum ChelicerataGeneral Features

• 6 pairs of appendages include chelicerae,
  pedipalps 4 other pairs of appendages
• 1st pair called chelicerae, are pincerlike for
  feeding 2nd pair called pedipalps, are for
  feeding, locomotion reproduction
• They lack mandibles antennae

7
Subphylum ChelicerataClass Merostomata

• Horseshoe crabs (Limulus) scavenge the substrate
• Hard carapace covers the cephalothorax
• Has a long pointed telson
• Body has not changed for over 200 million years

8
Subphylum ChelicerataClass Arachnida

• Carnivores with 8 legs
• Feeds on insects, injecting venom which liquefies
  tissues
• Breathe by book lungs
• Malpighian tubules for excretion
• 8 simple eyes detect movement while setae detect
  web vibrations
• Spinnerets secrete silk to line burrows, spin
  webs wrap prey

9
Spiders contd

• Male stores sperm in his pedipalps
• Pedipalps are then inserted into female genital
  openings
• Courtship ritual takes place before mating
• Eggs develop in a cocoon young hatch in 2 weeks
  molt into mini adults

10
Spider diversity

• Tarantulas rarely bite are not dangerous
• Black widows are dangerous injecting a neurotoxin
• Brown recluse injects a hemolytic venom that
  destroys tissue

11
More Arachnids Scorpions

• Scorpions are nocturnal feed on insects
• Small chelicerae enlarged pedipalps
• Stinger has venom few are toxic to humans
• They perform a mating dance, walking back forth
• Development is internal for up to 1 1/2 yrs
• After birth, young crawl onto mothers back

12
More Arachnids Ticks Mites

• Most are ectoparasites on humans domestic
  animals
• Ticks bodies expand when engorged with blood.
  They feed for a few hours drop off
• Follicle mites are found in hair dust mites are
  found in dust cause allergies
• Itch mites cause scabies of the skin

13
Diseases caused by ticks

• Lyme disease is caused by bacteria on the tick
  which lives on deer
• The cattle tick transmits Texas cattle fever
• Another tick transmits the bacteria that causes
  Rocky Mountain spotted fever

14
Ch 14Subphylum Crustacea

• Crustaceans differ from other arthropods as they
  have 2 pairs of antennae (as opposed to 1 pr or
  none) also biramous appendages
• A biramous appendage has a basal segment with 2
  rami attached giving a Y-shaped look

15
Subphylum CrustaceaClass Malacostraca

• Crabs, lobsters, shrimp
• Shrimp have a compressed, muscular abdomen for
  swimming
• Lobsters crabs have a reduced abdomen for
  crawling on the sea floor
• Their bodies have 2 regions-the cephalothorax
  the abdomen

16
Class Malacostraca contd

• The exoskeleton of the cephalothorax forms a
  carapace that acts as a protective shield
• Paired appendages on the cephalothorax of a
  shrimp include 2 pairs of antennae1 pair of
  mandibles for chewing 2 pairs of maxillae for
  handling the food for circulating water over
  gills 3 pairs of maxillipeds which have gills
  then 5 pairs of periopods or walking legs (the
  1st pair of periopods is a large cheliped for
  defense)

17
Malacostraca contd

• Paired appendages on the abdomen include 5 pairs
  of pleopods or swimmerets for swimming
• In females the eggs attach to the pleopods until
  they hatch in males the 1st 2 pairs of pleopods
  are used for sperm transfer
• The abdomen ends in the telson which has 2
  flattened segments called uropods used like
  flippers when swimming

18
Respiratory Circulatory Systems

• Gills are attached to the base of the appendages
  on the cephalothorax
• The beating of the maxillae drives water over
  gills where oxygen carbon dioxide are exchanged
• Blood has a respiratory pigment called hemocyanin
• Open circulatory system where vessels empty into
  sinuses

19
Nervous System

• Cephalization - sensory receptors in the head
  send signals to the brain
• Nerve impulses travel along giant neurons in the
  ventral nerve cord to flex powerful muscles in
  the abdomen
• The telson uropods form a paddle-like tail that
  propels the crayfish backwards

20
Nervous System contd

• In addition to antennae, they have compound eyes
  on moveable stalks, statocysts at the base of
  each antenna for balance, chemoreceptors over the
  appendages the head for sampling food
  detecting pheromones

21
Excretion Reproduction

• Crustaceans have green glands at the base of the
  2nd antennae to excrete ammonia
• They are dioecious (separate sexes)
• Gonads are in the thorax
• Mating occurs after female molts male turns her
  over on her back deposits sperm near her
  goniducts
• Eggs fasten to her pleopods, she fans her
  pleopods to aerate the eggs. Eggs hatch into mini
  adults. Some have a swimming larva instead

22
Other members of Class Malacostraca

• Isopods (or Pillbugs) roll into a ball when
  disturbed
• Amphipods (or Beachhoppers) hop along the beach
  sand

23
Other classes of Crustaceans

• Class Brachiopoda includes the fairy shrimp
  the brine shrimp which live in ponds water fleas
  live in lakes
• Class Copepoda includes the copepods, the most
  abundant crustaceans. They are planktonic food
  for many animals in the sea
• Class Cirripedia includes the barnacles. They
  attach to the bottom of ships, whales, rocks

24
Barnacles, Copepods Fairy Shrimps
25
Molting or Ecdysis

• Molting is needed for crustaceans to grow
• The underlying epidermis secretes the cuticle
• Enzymes dissolve the old cuticle animal swallows
  water to expand burst the old cuticle
• New cuticle stretches hardens
• Temperature, length of day may trigger the
  nervous system to begin molting
• This promotes the release of molting hormone
  which leads to molting

26
Ch 15 Subphylum Uniramia

• Subphylum Uniramia consists of Class Diplopoda
  (millipedes), Class Chilopoda (centipedes)
  Class Hexapoda (insects)
• They all have a head with one pair antennae one
  pair mandibles appendages are uniramous

27
Class Diplopoda

• Millipedes
• Two pairs of appendages per segment
• Most have rounded bodies
• They are found under logs, or in leaf litter
  feed on decaying plants
• They roll into a ball if disturbed
• Repugnatorial glands produce hydrogen cyanide to
  repel predators

28
Class Chilopoda

• Centipedes
• Flattened bodies
• Single pair of legs on each segment
• Last pair is modified into long sensory
  appendages
• Fast moving predators
• Poison claws kill or immobilize prey

29
Class Insecta (or Hexapoda)

• Insects are the most diverse abundant
  arthropods the ability for flight makes them be
  widely distributed
• Found in all habitats except the ocean
• 3 pairs of legs 2 pairs wings
• Body divided into head, thorax abdomen
• Head has 1 pair antennae, mouthparts, compound
  eyes
• Abdomen has 9 to 11 segments, each having a fold
  in the exoskeleton to allow for expansion

30
Insect Flight

• Wings are thin membranous
• Flight muscles attach to the wings directly
• High body temperatures are needed for flight
  muscles to contract enough for flight
• Some insects use direct or synchronous flight in
  which muscles at the base of wings contract to
  give a downward thrust muscles dorsally
  ventrally contract to give an upward thrust

31
Insect Flight contd

• In indirect or asynchronous flight, muscles
  change the shape of the thorax which causes the
  wings to move up down
• During a wingbeat, the thorax is deformed,
  storing energy in the exoskeleton
• Midway into downstroke, stored energy reaches a
  maximum energy is released
• Asynchronous muscles only need occasional nerve
  stimulation - a single nerve impulse can result
  in 4 cycles per second in butterflies over
  1,000 in midges

32
Other forms of insect locomotion

• Insects can walk, run, jump swim
• When they walk, they have 3 or more legs on the
  ground but when they run, they may have fewer
  than 3 legs touching the ground
• Their small size ability to change directions
  enables them to run fast
• Cockroaches can go 5 km/hr fleas can jump up to
  100 times its body length

33
Nutrition in Insects

• Foregut consists of mouth with salivary glands,
  esophagus, crop gizzard
• Midgut is the main site of digestion absorption
  where gastric ceca secrete digestive enzymes
• Hindgut is where water gets absorbed
• Most insects feed on plants or juices
• Beetles insect larvae eat dead animals
• Some are predators while others are parasitic

34
Circulation Gas Exchange in Insects

• Tubular heart moves blood containing nutrients,
  homones wastes but blood is not involved in gas
  exchange
• Gas exchange involves a network of tracheal tubes
  that branch throughout the body with spiracles
  opening to the outside
• Insect can close spiracles to stop water loss or
  filter out dust

35
Special methods of breathing by insects

• Diving beetles keep a bubble of air (known as an
  artificial gill) under their wings
• Mosquito larvae have short breathing tubes to
  snorkel the air on the water surface
• Maggots of some flies have an extensible tail
  that stretches up to water surface
• Some insects have air sacs in the body cavity.
  These sacs are tracheae that become enlarged when
  abdominal muscles suck in air

36
Excretion Nervous System of Insects

• Insects ( spiders) use malpighian tubules to rid
  the body of uric acid. Water salts are
  reabsorbed in the rectum
• Insects have mechanoreceptors on antennae, legs
  body that can sense touch, pressure vibrations
• Sensitive setae detect sounds in the air
• Organs in legs detect vibrations
• Chemoreceptors located in sensory pits on
  antennae, mouthparts legs can detect odors from
  afar

37
Insect eyes

• Insects have simple eyes compound eyes
• Compound eyes consist of thousands of ommatidia
  that fuse together allow them to see in almost
  all directions
• Bees can detect UV light but they cant see red
  color
• Insects see fuzzy images. Their eyes are better
  at detecting movements

38
Insect Reproduction

• Sexes are separate fertilization is internal
• Factors that affect reproductive activitiy
  include availability of food, length of daylight
  hours, population density, temperature, humidity
• Mating behaviors involve pheromones (moths),
  visual signals (fireflies), and auditory signals
  (crickets)
• Sperm is deposited in the female reproductive
  tract during copulation. Eggs are fertilized as
  they leave the females body

39
Metamorphosis

• Insects change their body forms due to the
  presence of the hormone ecdysone
• Each stage between molts is called an instar.
  Wings develop during last stage
• Holometabolous metamorphosis (egg-larva-pupa-adult
  ) is where larvae adults live in different
  environments do not compete
• Larval moth or butterfly becomes a pupa inside a
  cocoon. Adult later emerges
• Hemimetabolous metamorphosis is egg-nymph-adult
  (incomplete metamorphosis)

40
Insect Defense Mechanisms

• Some insects have warning coloration while some
  mimic poisonous ones
• Stink bugs have repulsive odors taste
• Ants bees can be aggressive
• Bombardier beetle sprays its enemies with
  irritating chemicals

41
Insect Communication

• Insects secrete chemicals called pheromones that
  affect the behavior of another insect
• Pheromones attract the opposite sex, fend off
  aggression, warn others,or mark trails
• Insects also use sounds to warn others in
  courtship songs
• Some insects tap, stroke, or grasp each other or
  touch their antennae
• Some use bioluminescence to flash lights in a
  pattern

42
Round Dance Waggle Dance

• Bees communicate the location of food to others
  bees in the colony
• Incoming bees perform a round dance a waggle
  dance
• Other bees touch the dancing bees with their
  antennae to sense the odors of the pollen nectar

43
Round Dance contd

• Incoming bee moves in a semicircle to the left,
  then in a straight line toward the starting point
• During the straight line part the bee waggles its
  abdomen
• The angle that the waggle dance makes with the
  hive tells the direction of the food the of
  waggles tells the distance

44
Social Behavior of Insects

• Different members of a colony are specialized in
  structure behavior to perform different tasks
• The caste system is seen in bees, ants, wasps
  termites. Each kind of individual is a caste
• There are 4 castes in a colony - queens are the
  reproductive females workers are sterile males
  or females who maintain protect the colony
  male drones inseminate the queen soldiers are
  sterile defend the colony

45
Whos the Boss??

• The Queen bee releases a pheromone that controls
  the caste system
• Workers lick groom the queen pass this
  pheromone onto other workers. This stops them
  from rearing any new queens.
• As the queen gets old, she puts out less
  pheromone workers begin to feed royal jelly
  to several female larvae. This food promotes
  development of queen features
• The queens fight until one remains. She goes on a
  mating flight returns to the hive to live

46
Parthenogenesis

• Drones are produced by parthenogenesis, a process
  in which eggs develop without being fertilized by
  male sperm
• Drones are genetically identical to the queen bee
  therefore have less genetic variation than
  other bees who have chromosomes from both parents

47
How Insects Affect Us

• Insects produce wax, honey silk
• They pollinate many plants crops
• They are biological control agents
• Some help the soil by improving drainage,
  aeration, by promoting decay processes
• Insects are food for other animals
• Some are parasites vectors of diseases such as
  malaria, yellow fever, bubonic plague
• Others feed on crops cause diseases in plants

48
(No Transcript)