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Arthropods
What is Entomology?
The study of insects
(and their near relatives).
What are insects
(and near relatives)?
Insects and their relatives are
ARTHROPODS.
Review of Zoological Nomenclature
(classifying & naming)
Taxonomic Categories
Phylum
Class
Order
Family
Genus
Genus & species
Review of Zoological Nomenclature
Taxonomic Categories
Kingdom - Animalae
Phylum - Arthropoda
Class - Insecta
Order - Coleoptera
Family - Scarabaeidae
Genus - Popillia
Genus & species
Popillia japonica Newman
What are some other
Animal Phyla?
Porifera & Cnidaria – sponges & corals.
Platyhelminthes - flatworms, tapeworms
Nematoda - roundworms
Mollusca - clams, snails & slugs, squids
Echinodermata - starfish, sea urchins
Annelida - segmented worms
(earthworms)
Chordata - fish, amphibians, reptiles,
birds, mammals
Characteristics of the Phylum
Arthropoda
The segmented bodies are arranged into
regions, called tagmata (e.g., head, thorax,
abdomen).
The paired appendages (e.g., legs, antennae)
are jointed.
They posses a chitinous exoskeletion that
must be shed during growth.
They have bilateral symmetry.
The nervous system is dorsal (belly) and the
circulatory system is open and ventral
(back).
Arthropod Groups (taxa)
The arthropods are divided into two
large groups that exist today:
Chelicerates
and
Mandibulates
Chelicerate Arthropod Characters:
Pincher-like mouthparts chelicerae - and pedipalps
NO antennae
Two body regions, usually cephalothorax & abdomen
Four pairs of legs
Horseshoe crabs and arachnids
are only living groups
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Divided into 3 classes; Arachnida, Merostomata &
Pycnogonida
Body divided into 2 regions
Abdomen
 Cephalothorax (fused head & thorax)
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Lack jaws
Have 6 appendages & no antennae
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First appendages form chilicerae (frequently fangs)
Mandibulate Arthropod Characters:
Mouthparts are mandibles - normally
chewing sideways
One or two pairs of antennae
Various body region arrangements cephalothorax & abdomen / head &
trunk / head, thorax & abdomen
Variable leg numbers
Insects, crustaceans & myriapods
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The three main classes of arthropods are:
insects (cockroaches, ants, flies, bees, beetles
and butterflies), crustaceans (crabs, lobsters,
shrimp and barnacles) and arachnids
(scorpions, spiders and mites).
Other classes are onychophorans (velvet
worms), diplopods (millipedes) and chilopods
(centipedes).
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Morphology is a branch of biology dealing
with the study of the form and structure of
organisms and their specific structural features.
Arthropods present three distinguishing
features: they are metameric organisms
(segmented body), they have an exoskeleton
made of chitin and they have articulated limbs.
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Germ layers :each of the three layers of cells
(ectoderm, mesoderm, and endoderm) that are
formed in the early embryo.
Gastrulation is a phase early in the embryonic
development of most animals during which the
single-layered blastula is reorganized into a
trilaminar ("three-layered") structure known as
the gastrula. These three germ layers are
known as the ectoderm, mesoderm, and
endoderm .
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A blastula is an animal embryo at the
early stage of development when it is a
hollow ball of cells
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Arthropods are triploblastic (they have
three germ layers) and are coelomate
organisms.
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Given their metameric structure, arthropods
are evolutionarily closer to annelids, as they
also have segmented bodies. In the embryonic
development of some arthropods the fusion of
metameres takes place, forming structures such
as the cephalothorax of arachnids, for example.
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The external shell of arthropods is called the
exoskeleton. The exoskeleton of an arthropod is
made of chitin, a nitrogen-containing
polysaccharide.

Due to the presence of the exoskeleton, the
growth of arthropods is periodical. During the
growth period, the animal loses the
exoskeleton, grows and develops a new
exoskeleton. This process is called ecdysis or
molting.
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arthropod video
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Since they have an exoskeleton and periodic
ecdysis, the growth of arthropods is limited to
lessen the organisms' vulnerability to
environmental harm. However, some
arthropod species contain relatively large-sized
species, such as “giant” cockroaches, crabs and
spiders.
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http://news.discovery.com/animals/videos/a
nimals-ticks-bloodsucking-ninjas-ofsummer.htm
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In the exoskeleton of arthropods, there is a
layer of waterproof wax. This feature was
fundamental in allowing primitive arthropods
from the sea to survive on dry land without
losing excessive water to the environment.
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The digestive tract of arthropods is complete,
containing a mouth and an anus. Arthropods
are protostome animals, meaning that the
blastopore produces the mouth, during their
embryonic development.
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As typical aquatic animals, crustaceans
contain highly vascularized gills that are in
contact with water and permit gas exchange.
In terrestrial insects, respiration is tracheal
and gases flow inside small tubes that
connect the animal's external surface with
tissues and cells without the participation of
blood. In arachnids, in addition to tracheal
respiration, book lungs (thin folds
resembling the pages of a book) may also
exist.
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In arthropods, the respiratory system is open (lacunar).
Blood, also known as hemolymph, is pumped by the
heart and enters into cavities (lacunas), irrigating and
draining tissues.
All arthropods have a heart. Crustaceans and
arachnids have respiratory pigments. Most insects do
not have respiratory pigments, since their blood does
not carry gases (in insects, gases reach tissues and cells
through tracheal structures). However, some insects do
have the respiratory pigment hemoglobin
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Respiratory pigments are molecules able to
carry oxygen and other respiratory gases
present in circulatory fluids.
In crustaceans and in arachnids, hemocyanin is
the respiratory pigment. In humans, the
equivalent pigment is hemoglobin.
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In crustaceans, a pair of excretory organs called
green glands exists. The green glands collect
waste from the blood and other parts of the
body. They are connected to excretory pores
located under the base of the antennae via
ducts. These pores excrete this waste outside
the animal.
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In insects, small structures called malpighian
tubules remove waste from the blood. moving
it into excretory ducts that open into the
intestine. In these animals, excretions are
eliminated together with feces.
In arachnids, in addition to malpighian
tubules, there are coxal glands located in the
cephalothorax near the limbs that are also
involved in excretion.
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In arthropods, the nervous system has more
sophisticated sensory receptors with advanced
cephalization. In the anterior region of the body, there
is a group of ganglia which form a brain connected to
two ventral ganglial cords that contain motor and
sensory nerves.
The increased development of the sensory system of
arthropods provides more possibilities for these
animals to adapt and, as a result, a greater ability for
them to explore many different environments.
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Arthropods have compound eyes made of
several visual units called ommatidia. Each
ommatidium transmits visual information
through the optic nerve to the brain, which
interprets the image. These ommatidia are
round and numerous, and their external
surfaces point in different directions creating
independent images.
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This causes arthropod eyes have a visual field
larger than that of vertebrates. Some insect
have one or more simple eye in addition to
their pair of compound eyes.
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Reproduction in animals of the phylum
Arthropoda is sexual, with a larval stage in
some insects and crustaceans (arachnids only
go through direct development).
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Nymphs are the larvae of hemimetabolous
insects (such as grasshoppers). They are very
similar to the adult insect, although smaller. In
holometabolous insects (such as butterflies),
the larva makes a cocoon (chrysalis, pupa)
where it lives until transforming into the adult
form. Imago is the name given to the adult
form of insects with indirect development.
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having no pupal stage in the transition from
larva to adult.
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characterized by complete metamorphosis
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Crustaceans and arachnids do not have wings.
Most insects have wings.
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Crustaceans have two pairs of antennae; insects
have one pair; arachnids do not have antennae.
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In crustaceans and arachnids, the head is fused
with the thorax to form the cephalothorax.
Their body is therefore divided into
cephalothorax and abdomen.
Insects have a head, thorax and abdomen.
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Insects are the animal group with the greatest
diversity of species. Almost 750,000 insect
species are known, making up approximately
55% of the total already recorded species of
living organisms (compare this with mammals,
with no more than 4,000 known species).
However, scientists estimate that the number of
unknown species of insects may be over 2
million.
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The insect population on the planet is estimated to be
more than 10 quintillion (10,000,000,000,000,000,000).
The evolutionary success of insects is due to factors
such as their: small size and diversity of foods, which
make it possible for them to explore many different
ecological environments; wings, which provided them
with a greater area to spread across; tracheal
respiration, which makes them highly agile; high
reproductive rates, which produces a large number of
offspring.
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Insects such as some species of bees, wasps, ants and
termites form societies that contain hierarchies and the
division of jobs among their members. Spiders build
sophisticated external structures, their webs, mainly to
serve as a trap for capturing prey. Another example is
the communication mechanism in some bees known as
the bee dance, through which one bee tells others
information about the location of flower fields and
other sources of nectar.
Orders of Arachnids
Scorpions
Pseudoscorpions
Daddy Long-Legs
Mites & Ticks
Spiders
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Very diverse class
Most species parasitic
or predatory
Many possess book
lungs for gas exchange
Spiders are able to
produce a strong
polymer - silk
Chilicera in form of
fangs
Tarantula
Black Widow
The brown recluse and its bite wounds
Dust Mite
Common Mite
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Ancient group of
species
Changed little over
350 million years
Aquatic, mostly
found on Atlantic &
gulf coasts of
United States
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https://www.youtube.com/watch?v=c5M2cL
50V1A
https://www.youtube.com/watch?v=c6ZMKc
2NrZ8
https://www.youtube.com/watch?v=5o3bUL
LLy44
http://www.discovery.com/tvshows/mythbusters/videos/daddy-longlegsminimyth/
Pseudoscorpion
Scorpion
Daddy-long-legs
Tick
(a mite)
Wolf
Spider
Scorpion Anatomy
chelicerae
eyes
pedipalp
Pseudoscorpion
Mite and Tick Body Regions
pedipalps &
chelicerae
cephalothorax
abdomen
American dog tick male
Blacklegged (deer) tick female
American dog tick female laying egg mass (1000-2000 eggs!).
Clover mites
Twospotted spider mites
Predatory mite
daddy long-legs
cephalothorax
abdomen
Spider Anatomy
pedipalp
chelicera (fang)
cephalothorax
narrow waist
abdomen
Jumping Spider
Abdomen
Cephalothorax
Chelicera (fang)
Pedipalp
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http://www.nytimes.com/video/science/100
000003209530/inside-a-jumping-spidersbrain.html
Wolf spider with egg case
Tarantula
Spitting spider
Orb-weaving spider
Black widow with egg case
Brown recluse
Classes of Myriapods
(many legged arthropods)
(all have one pair of antennae, a head region, and trunk
with many pairs of legs, use trachea)
Diplopoda - millipedes
Chilopoda - centipedes
Myriapods
[one pair of antennae, head & trunk regions, trunk with many pairs of legs]
Millipede (Diplopoda)
Two pair of legs per visible segment, attached
under body.
Centipede (Chilopoda)
Pair of fangs under head, one pair legs per visible
segment - attached to side of body.
No fangs, no eyes, legs attached to side of body.
Millipede (Diplopoda)
Centipede (Chilopoda)
Garden centipede
Classes of Crustacea
• mostly marine, fresh water, a few terrestrial
• all have two pair of antennae
• five or more pairs of legs
• segmented abdominal appendages
• head & trunk or cephalothorax & abdomen body
arrangement
• have gills
Sowbugs or pillbugs
Sand fleas
Barnacles
Crabs, lobster, shrimp
Crayfish cephalothorax
(Decapoda)
Sowbug (Isopoda),
a terrestrial crustacean