Arthropods

1
Arthropods
2
Phylum Arthropoda

• Greek for jointed feet
• Crabs, shrimp, barnacles, Insects, spiders etc.
• Largest phylum of animals with 1 million known
  species
• Of all the animals on earth, 3 out of 4 are
  arthropods
• Have a tremendous ability to take advantage of
  just about every habitat.

3
Phylum Arthropoda

• Evolution of exoskeleton
• Composed of chitin
• Tough, rigid material allows for great protection
  and support
• Causes limitation in size
• In order to grow the arthropod must molt its
  exoskeleton
• You wont see an arthropod as big as a squid or a
  whale
• Right after molting arthropods are at their most
  vulnerable state

4
Phylum Arthropoda

• Bilaterally symmetrical
• Coelomate
• Segmented Body
• Divided into 3 segments head, thorax and abdomen
  
• Evolution of jointed appendages
• Increased mobility / flexibility (legs)
• Modified for feeding and senses (mouthparts)
• Used for protection

5
Arthropod Biology

• Digestion
• Filter feeding, scavengers, predators
• Appendages closest to the mouth, such as the
  maxillipeds, are specialized to sort out food and
  push it toward the mouth.
• 2 chambered stomach that has chitinous teeth or
  ridges for grinding and bristles for sifting.
• Open Circulatory System
• Respiratory System
• Arthropods have developed 3 types of respiratory
  structures depending on their environment gills,
  tracheae, or book lungs

6
Arthropod Biology

• Acute Senses
• Many produce pheromones (a chemical odor) in
  order to communicate and have highly developed
  senses
• Most have one pair of large compound eyes and 3
  to 8 simple eyes
• A simple eye is a visual structure with only
  one lens that is used for detecting light
• A compound eye is a visual structure with many
  lenses. Each lens registers light from a tiny
  portion of the field of view
• Reproduction
• Separate sexes with internal fertilization

7
Arthropod Biology

• Niche (What they do / their role)
• Arthropods are of great direct and indirect
  importance to humans
• The larger crustaceans--shrimps, lobsters, and
  crabs--are used as food throughout the world

• Small planktonic crustaceans, such as copepods,
  water fleas, and krill, are a major link in the
  food chain
• Approximately two-thirds of all flowering plants
  (angiosperm) are pollinated by insects
• They function as decomposers
• Arthropods are major carriers of disease

8
Phylum Arthropoda

• 3 Subphylums
• Chelicerates
• Crustaceans
• Uniramia

9
Subphylum Chelicerates

• General Characteristics
• Chelicerates have six pairs of appendages, which
  are uniramous (unbranched)
• include a pair of chelicerae, a pair of
  pedipalps, and four pairs of walking legs
• Lack mandibles and antennae
• Respiration is by means of book gills, book
  lungs, or tracheae.

10
Subphylum Chelicerates

• 3 classes
• Merostomata - horseshoe crabs
• Pycnogonida - sea spiders
• Arachnida - spiders, ticks, mites

11
Class Merostomata

• Horseshoe Crabs
• Carapace covering body
• Cephalothorax, abdomen, telson
• 6 pairs of appendages
• Research using blood

12
1. Class Merostomata

• two different groups of marine organisms
• the eurypterids and the horseshoe crabs
• Eurypterids are now extinct (they lived 200 to
  500 million years ago)
• Horseshoe crabs feed on small invertebrates
• Members of this class have a large shield that
  covers the cephalothorax.
• The compound eyes are reduced
• The second pair of appendages, the pedipalps,
  resemble walking legs.
• They have a long, spike-like appendage called a
  telson that projects from the rear of their
  bodies.
• The horseshoe crab uses its telson to flip itself
  over if it got flipped on its back. It is not
  used for defense as one might suspect.
• Respiration is via book gills.

13
1. Class Merostomata
14
2. Class Pycnogonida

• An example is a sea spider
• Sea spiders appear to be a sort of marine
  "spider,"
• approximately 1000 described species all are
  marine
• They feed by sucking juices from soft-bodied
  invertebrates through a long proboscis.
• The body itself is not divisible into neatly-
  organized tagmata or regions as it is in most
  other arthropods.
• An anterior region bears, besides the proboscis,
  three or four pairs of appendages, including the
  first pair of walking legs.

15
2. Class Pycnogonida
16
3. Class Arachnida

• Spiders, ticks, mites, scorpions
• over 60,000 described species spiders make up
  the majority of those known species
• They have 8 legs instead of 6 like insects have
• Nearly all species are terrestrial
• Respiration is via tracheae or book lungs
• They have a two-segment body, made up merely of
  the thorax and abdomen.
• The pedipalpi (leg-like mouthparts) of some
  species has instead been adapted for sensory,
  prey capture or reproductive functions.

17
3. Class Arachnida

• Arachnids are mostly carnivorous, feeding on the
  pre-digested bodies of insects and other small
  animals.
• Many are venomous - they secrete poison from
  specialized glands to kill prey or enemies.
• Others are parasites, some of which are carriers
  of disease.

18
Arachnids
19
Subphylum Crustacea

• Barnacles, crabs, shrimp, etc.
• Head, thorax, abdomen
• Specialized appendages--antennae, mandibles,
  maxillae

20
(No Transcript)
21
Class MalacostracaOrder Decapoda

• 5 Pairs of walking legs
• Crabs, shrimp, lobsters
• Krillimportance to food chain
• Unique pattern of segmentation among crabs

22
Class Cirripedia

• Barnacles
• Filter feeders
• Sessile (including on other living organisms)
• Feathery appendages (legs) to filter food
• Larvae swim then attach for metamorphosis

23
Class Copepoda

• Copepods
• Important plankton
• Filter feeders
• Stay afloat by enlarged appendages
• Many parasitic