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PHYLUM
ARTHROPODA
Arthropoda Characteristics
• account for over 80% of all living animal
species
Arthropoda Characteristics
• means “jointed foot”
• True coelom
• exoskeleton made of chitin
• show a high degree of cephalization
– variety of segmented antennae used for sensing
the environment and detecting chemicals
– most have compound eyes & other light sensing
structures
• body plan of repeated segments that attach
to an appendage
Arthropoda Characteristics
• open circulatory system
– Heart pumps circulatory fluid thru
vessels that empty into spaces in the body
• nervous system is ladder-like with
brain formed from fused ganglia
• Respiratory system varies with each
species.
Life cycle
• Stage 1: Egg – females lay thousands of eggs. Some #
survive
• Stage 2: juvenile
each has different names to describe this
stage (example: lice – nymph)
• Stage 3: Molting – shedding or physical change before
adulthood
• Stage 4: Adulthood – those surviving can reproduce.
Most fertilization of eggs inside female then
released to hatch.
Phylum Arthropoda classes
• 5 major classes:
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Chilopoda – centipedes
Diplopoda – millipedes
Crustacea – crabs, lobster, crayfish,shrimp
Insecta – insects
Arachnida – spiders, scorpions, mites, chiggers
Classification of Arhtropoda
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Centipedes – 1 pr legs/segment
Millipedes – 2 prs legs/segment
Crustaceans – 5 pairs of legs
Insects – 3 pairs of legs
Arachnids – 4 pairs of legs
Class Diplopoda
• 1000 leggers
• millipede
• Cylindrical worm-like with 2/prs legs/seg.
Juveniles may possess only 1 pair per segment
• Simple eyes if any present. Many have no eyes
• Decomposers or herbivores
• Short antenna
• Non-toxic
Diplopoda Characteristics
• Very timid
• Protect by rolling themselves up tight and
discharge a foul smelling, distasteful
substance.
• Fertilized eggs are laid in the soil.
• They are found in cool, moist environments.
Found under rocks and logs.
Class Diplopoda
Class Chilopoda
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Centipedes
100 leggers
Flattened worm like w/1 pr legs/seg
Carnivores
Possess a pair of poison claws or legs just behind the head
which are used to paralyze their prey
Feed on insects or small animals
Most centipedes are beneficial
Large species found in the tropics (length of up to 18 inches)
Can inflict painful bites
More Chilopoda characteristics
• Simple eyes
• The bite of centipedes can be painful to humans but
not deadly.
Life Cycle:
• Males spin web where they deposit sperm for females
to pick up.
• Sometimes there is a courtship of dancing or tapping.
Habitat:
• Like millipedes can be found under rocks, logs, or bark
of tree.
Class Chilopoda
Class Insecta
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Upwards of 3 million species
Outnumber all other plant and animal groups
Found in all environments
Some fly hundreds of KM per week
Class Insecta
• Three body divisions
– Head
– Thorax
– Abdomen
• 12 Inches—Largest
• 1MM-Smallest
• Rapid growth rate
• Most mature < 1 year
• Display almost every color
Class Insecta
• Spiracles (external openings)
along abdomen used for
breathing
• Highly modified mouth parts
(mandibles)
– Some beetles can chew
through lead or zinc
• Well developed tube within a
tube digestive system
• Well developed nervous
system
• Sight: two types of eyes (Ocelli
and compound eyes)
• Smell/taste-Use of antennae
and feet
• Hearing- tympanum (eardrum)
Defense
Insects use can use a
variety of defenses:
• Hiding
• Burrowing
• Mimicry
• Shedding appendages
• Chemical defense
• Camouflage
• Warning colors
Insects and the Economy
Insects have direct impact on agricultural food
production
• Chewing leaves
• Sucking out plant juices
• Boring into roots
• Spreading plant pathogens
• Can transmit diseases
Benefits
Insects play a role in the cycle of nutrients on Earth.
• Help aerate soil
• Improve soils retention of rainwater
As parasites and predators
• help with community stability
• prevents over population growth
• Insects help pollinate
Other benefits:
• Produce honey to eat
• Beeswax
• Silk from silkworms
Insect Reproduction
Reproduction is most often sexual
• Parthenogenesis is asexual reproduction – species can form
from unfertilized eggs. Example bees – unfertilized produce
males, fertilized can produce females
Females:
• Make eggs
• Receive sperm and store it
• Able to manipulate sperm from different males
• Number of eggs an insect lays can vary
Males:
• Reproductive system consists of testis
Class Insecta
• Pheromones- External
hormones used for
communication
(especially in finding
mates)
Crustacea
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Body segmented with hardened Limbs
Limbs generally with two branches
Two pairs of antennae
Two compound eyes (eyes with many lenses)
Body with 7 or more pairs of sometimes very different
appendages for feeding, locomotion and sex
• Respiration by gills
• Nauplius- Distinctive larval stage with three pairs of branched
appendages
• Although originally aquatic, many crustaceans are adapted to
life on land
Crustacea
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Shrimp
Lobster
Krill
Pill bug
Crabs
Crayfish
Barnacles (sessile)
Crustacea
http://www.youtube.com/watch?v=eKPrGxB1Kzc
Class Arachnida
• Spiders
• Mites/ticks
• Scorpions
Class Arachnida
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Most familiar spiders
head (fused to thorax) and abdomen
All toxic
No antennae
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Many, but not all spiders web builders
Liquid feeders
Inject digestive enzymes into prey and drink juices
Use powerful jaws to crush exoskeleton- then digest and eat
Class Arachnida