Download Phylum Arthropoda Non

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Makes up 3/4's of all animal species
Includes insects, spiders, scorpions, millipedes, centipedes,
crabs, lobsters, & crayfish
Arthropod means "jointed foot"
Jointed appendages (legs, antenna, mouthparts)
Segmented body with paired appendages on each segment)
External exoskeleton made of chitin (carbohydrate) &
protein for protection & support
Exoskeleton has 3 layers --- outer waxy layer repels water,
middle layer has calcium for extra strength, & inner layer
has flexible joints for movement
Protostomes (blastopore develops into mouth)
Coelomate (mesoderm-lined body cavity)
Ventral nervous system
Open circulatory system
Specialized sensory receptors & high degree of
cephalization
Have simple or compound eyes & segmented antenna
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Muscles occur in bundles & are attached to inside
of exoskeleton on each side of joints
Exoskeleton must be periodically molted (shed) for
organism to grow
Molting called ecdysis
Tissues swell and put pressure on old exoskeleton
Molting hormone released & causes epidermal cells
to secrete enzymes that digest & loosen inner
exoskeleton
New exoskeleton secreted by epidermal cells
flexible at first & must harden so arthropod not
vulnerable to predators so often stay in hiding after
molting
Arthropods go through numerous molts
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Evolved from ancestral arthropod with
many body segments each with
appendages
Modern arthropod segments fused into
larger, specialized structures called
tagmata
Four subphyla
* Trilobita - extinct trilobites
* Crustacea - shrimps, lobsters,
crayfish,
& barnacles
* Chelicerata - spiders, scorpions, &
ticks
* Uniramia -centipedes, millipedes
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Includes extinct
trilobite
Marine
Have a head &
segmented trunk with
one pair of legs on
each segment
Breathe through gills
Single pair of antenna
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Includes 2 classes --- Xiphosura or Merostomata
(horseshoe crab) and Arachnida (spiders, ticks,
scorpions, & mites)
Have a cephalothorax (fused head& thorax) and
abdomen
No antenna
Simple eyes or ocelli
Have 6 pairs of jointed appendages:
* Chelicerae - claws or fangs (1 pair)
* Pedipalps - used for feeding, walking,
sensing, transferring sperm (1 pair)
* Walking legs - movement (4 pairs)
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Horseshoe crab
* Marine
* Not true crabs
* Fanglike
pincers or
chelicerae
* Use book gills
to breathe
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Terrestrial
Body divided into a cephalothorax and
abdomen
The cephalothorax usually has six pairs of
jointed appendages
* Four pairs of legs
* Chelicerae or fangs with venom
* Pedipalps
* No antenna
Breathe by book lungs &/or tracheal tubes
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Arachnid that feeds on insects (carnivores)
Have oval shaped, unsegmented abdomen
Cephalothorax connected by narrow waist to
abdomen
Have 8 simple eyes or ocelli
Fangs pierce prey, inject poison, & suck out body
fluids
Pedipalps on head help sense prey & move it to the
mouth
Open circulatory system
Ostia are openings in heart where blood reenters
Body cavity called hemocoel
Hemocycanin is oxygen-carrying pigment in blood
Have silk glands to make silk & spinnerets to
release silk for webs
Breathe by book lungs & tracheal tubes
Malpighian tubules filter wastes & reabsorb
water
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1.
2.
Adaptations for a predatory life on land
Book lungs = paired sacs in the abdomen
with many parallel folds that resemble the
pages of a book. The folds in a book lung
provide a large surface area for gas
exchange. (and/or)
Tracheae = a system of tubes that carry air
directly to the tissues from spiracles in the
exoskeleton.
3. Malpighian tubules = hollow projections of
the digestive tract that collect body fluids
and wastes and carry them to the intestine.
After most of the water is absorbed, the
wastes leave the body in a nearly solid form
with the feces. This helps spiders conserve
water.
And/Or
4. Coxal glands = organs that remove wastes
and discharge them through openings at
the base of some of the legs.
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Parasitic arachnid
Fused cephalothorax & abdomen
Most abundant arachnid
Need blood meal to molt
Mites can damage fruit & feed on dead skin at
base of hair follicle (extremely small parasitic
or free-living)
Ticks carry Lyme disease & Rocky Mountain
Spotted Fever (range in length from a few
millimeters to a little over 1inch and are
parasitic)
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Have a cephalothorax & long segmented
abdomen curled over body
Prefer dry regions
Poisonous stinger on end of abdomen
Breathe through book lungs
Pedipalps modified into claws
Nocturnal predators
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Marine members include shrimp, lobster,
copepods, barnacles, & crabs
Terrestrial crustaceans called isopods include
pillbugs & sowbugs
Freshwater members include crayfish &
Daphnia (water fleas)
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Have two pairs of appendages on their head that serve
as feelers
Usually have appendages on most other body segments
At least some of the appendages are branched
All have jaws or mandibles for chewing or tearing
Known as mandibulates
Have cephalothorax & abdomen
16 to 20 body segments
Have 10 pairs of jointed appendages
Most breathe through gills
Most have a nauplius larval stage
Aquatic crustaceans often incorporate large amounts of
calcium carbonate into their exoskeleton
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Barnacles
* Marine
* Sessile crustaceans that live in
limestone case
* Filter plankton with 12
appendages called cirri
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Live on land in dark places
Have 7 pairs of legs on a segmented body
Can roll into a ball for protection
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Cephalothorax made of 13 fused segments & covered
by protective carapace
Antennules located on head help in balance, touch, &
taste
Statocysts - balancing organs at the base of antennule
Antenna on head used for touch & taste
Maxillae - paired mouthparts that move side to side to
tear food
Maxillipeds - help hold food
Chelipeds - claws used to capture food & for protection
Mandibles - jaws that move up & down to crush food
Walking legs - 8 pairs used for movement
Swimmerets - under abdomen to swim, gas exchange,
& protect eggs/young
Abdomen ends in flat segment called telson with flat
uropods on each side
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Compound eyes on stalks
Chitinous teeth in stomach grind food
Wastes leave through anus
Green glands filter wastes from blood &
help with salt balance
Open circulatory system with heart to pump
blood to gills & body cells
Ostia - one way valves allowing blood from
dorsal sinus to reenter heart
Gills attached to walking legs
Separate sexes that mate in fall & sperm
stored in seminal receptacle
Eggs attach to swimmerets of female &
hatch in several weeks
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Know functions of appendages pg. 749
Digestion = food passes through the
esophagus to the stomach, where teeth made
of chitin and calcium carbonate grind the
food into a fine paste. The paste is mixed
with enzymes from the digestive gland then it
enters the intestine and the digestive gland
for further digestion and absorption.
Indigestible material leaves through the anus
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Respiration = as a crayfish walks, its legs
circulate water across its gills. Feathery
branches on the posterior pair of maxillae
also help direct water over the gills. Each gill
is covered by an extension of the exoskeleton
that is thin enough to permit gases to diffuse
across the gill surface.
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Circulation = the dorsal heart pumps
hemolymph into several large vessels that
carry it to different regions of the body.
Hemolymph leaves the vessels and enters the
gills, where it exchanges carbon dioxide and
oxygen with the water. From the gills, the
hemolymph returns to the dorsal part of the
crayfish and enters the heart.
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Excretion = water constantly enters the
tissues of a crayfish by osmosis. This excess
water is eliminated by green glands. The
dilute fluid is collected by the green glands
leaves the body through a pore at the base of
the antennae.
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Largest group of
crustaceans
Make up most of the
marine plankton
Serve as food for
many marine animals
Found in freshwater,
marine, & moist
terrestrial
environments
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All have antenna, mandibles (jaws), &
unbranched appendages
Single pair of unbranched antenna
Includes 3 classes --- Chilopoda
(centipedes), Diplopoda (millipedes), &
Insecta
Known as myriapods “many feet”
Most are terrestrial
Exoskeleton prevents desiccation (water
loss)
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Terrestrial centipedes
Flattened body with longer legs for fast
movement
Have 1 pair of legs per body segment
Predators
Mandibles & maxilla for chewing prey
(insects & earthworms)
Claw-like appendages or pincers on 1st
body segment that can inject venom
Can coil up for defense
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Terrestrial millipedes
Have 2 pairs of legs per body segment
Rounded body
Scavengers on decaying vegetation as they
burrow through soil
Roll into ball when threatened & spray
noxious chemical containing cyanide