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Arthropods
Jessica Corley
Andrew Lightfoot
Johnny Chen
General Arthropod Terms
 Cuticle: The exoskeleton of an arthropod, consisting of protein and
chitin that are variously modified for function
 Exoskeleton: A hard encasement on the surface of an animal that
provides protection
 Molting: The process in which the exoskeleton is shed at intervals to
allow growth by the creation of a larger exoskeleton
A cricket undergoing molting
 Book Lungs: Organs of gas exchange in spiders, consisting of
stacked plates contained in an internal chamber
General Terms (Cont..)
Open Circulatory System: An arrangement of internal transport in which
blood bathes the organs directly. There is no distinction between blood
and intestinal fluid
Chelicerae: Pointed appendages
which are used to grasp food;
some can contain venom glands
Mandibles: Pair of mouthparts used for eating that can actually chew food
unlike chelicerae
Antennae: Pair of sensory organs joined at the base, functions can vary
from organism to organism, including smelling, tasting, and sensing
vibrations (sort of like hearing).
General Terms (Cont……….)
 Compound Eyes: Eyes of an arthropod that consist of several ommatidia,
tiny independent photoreception units
 Malpighian tubules: Excretory organs that remove metabolic wastes from
the Arthropods
 Complete Metamorphosis: Arthropods with a larval stage that is made to
eat and grow. These arthropods look completely different from their adult
forms.
 Incomplete Metamorphosis: Arthropods that resemble adults during the
larval stages. With each successive molting, the arthropod becomes an
adult
 Tracheal System: Responsible for gas exchange in arthropods; consists of
branched, chitin-lined tubes that carry oxygen directly to the cells
 Spiracles: Pores that open to the outside of the body that open and close
to regulate air flow and reduce water loss
Exoskeleton
/ Cuticle
6
Compound eye
4
1
Chelicerae
Mandible
3
Antennae
2
Segmented
Legs
5
Dorsal View of Lobster
Classes
Arachnida
Body has one or two main part, six pairs Spiders,
of appendages (chelicerae, pedipalps,
scorpions,
and 4 pairs of legs) terrestrial
ticks, mites
Diplopoda
Body with distinct head bearing
antennae and mouthparts, segmented
body with 2 pairs of legs per segment
terrestrial, herbivorous
Millipedes
Chilopoda
Body with distinct head with antennae
and 3 pairs of mouthparts, first body
segment has poison claws, following
segments have 2 legs, terr., carnivore
Centipedes
Insecta
Body divided into head, thorax, and
Insects
abdomen, antennae, mouthparts
modified to chew, suck, or lap, 2 pairs of
wings, 3 sets of legs, most terr.
Crustacea
Body divided into two or three parts,
antennae, chewing mouthparts, 3 or
more pairs of legs, most marine
Crabs, lobsters,
Crayfish,
shrimp
A Few Orders of Insects
Coleoptera
Two Pairs of wings, armored
exoskeleton, biting and chewing
mouthparts, complete metamorphosis
Beetles
Diptera
One pair of wings and halteres
(balancing organs); sucking, piercing,
or lapping mouthparts, complete meta.
Flies,
Mosquitoes
Hymenoptera
Two pairs of membranous wings; head Ants,
mobile; chewing of sucking
Bees,
mouthparts; posterior stinging organ on Wasps
females; complete metamorphosis;
many species social
Lepidoptera
2 pairs of wings with tiny scales; long,
coiled tongue for sucking; complete
metamorphosis
Butterflies,
moths
Orthoptera
2 pairs of wings; biting and chewing
mouthparts; incomplete
metamorphosis
Crickets,
Roaches,
Grasshoppers
mantids
General Arthropod Information
Bilateral symmetry
3 Germ Layers, and a real
coelem
The more dominant body cavity
is called hemocoel. This is filled
with hemolymph, a mixture of
blood, lymph, and tissue fluid
Open circulatory system (the
cause of a hemocoel)
Protostomes
Lobster demonstrating bilateral
symmetry
Movement
Arthropods are sessile
Arthropods are
characterized by their jointed
appendages. These are how
they move.
In some cases, arthropods
use wings for movement.
Development
Most insects develop starting as eggs. The eggs hatch in larvae which is
the equivalent of a “baby.” Larvae transition into the adult stage through
metamorphosis—sometimes called molting—and become sexual active.
A prime example of this is the life cycle of butterflies which start as
eggs, hatch into caterpillars, and then go through a stage of dormancy
(known as Chrysalis) that eventually results in the butterfly.
Reproduction/ Life Cycle
Arthropods reproduce sexually. Male arthropods transfer
sperm through sealed packets called spermatophores.
The male can either lay it on the ground so that female
arthropods will pick them up or the male can deposit the
packet directly into the female.
After the eggs become fertilized, they can hatch from
periods ranging from a few days to years. Most species of
arthropods will lay the eggs in an external environment but
some species will hatch them internally.
The life cycle of an arthropod can range from a few weeks
to many years, depending the species.
Specialized Tissues/Functions
The exoskeleton of the Arthropod is built so that the hard section become
much thinner at joints.
Respiratory structures are specialized to adapt to the environment of the
Arthropod. For instance, lobsters have developed gills that allow them to
survive underwater.
Land-based Arthropods develop air-conducting tubes known as tracheas.
In order to adapt to the environment, Arthropods have specialized
sensory structures. Compound eyes are a prime example of this
occurrence.
Interesting, but Unnecessary Facts

Arthropods account for roughly 2/3 of all
known organisms. The estimated
number of Arthropods is around 1 billion
billion (1018)

Because both the Phylum Arthropod
and Phylum Annelids are segmented, it
was though for many years that both
shared a common ancestor. One of the
prevalent hypotheses was that
Arthropods descended from
Onychophorans (Walking worms).
However, recent study suggest that this
is not the case and that they share
common characteristics of bilaterians.
Cicada molting
*The process is sped up