Transcript The Arthropods:

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Blueprint for Success
Chapter 14 and 15
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Euglossa Bazinga
http://www.nydailynews.com/entertainment/tvmovies/bazinga-species-bee-named-big-bang-theorycharacter-catch-phrase-article-1.1232240
 Modified
segmentation –
body regions specialized for
specific functions
(tagmatization).
 Chitinous exoskeleton used
for support and protection
 Paired, jointed appendages
 Growth accompanied by
molting (ecdysis)
 Ventral
nervous system
 Reduced coelom
 Open circulatory system
where blood is released into
tissue spaces (hemocoel)
 Complete digestive tract
 Metamorphosis often present
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Successful in almost all habitats on the earth.
Most abundant animals – Several million species identified
o 30 to 50 million species may yet be undescribed
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Triploblastic, protostome development
Exhibit bilateral symmetry
Four aspects contribute to arthropod success.
o 1. Metamerism
o 2. Exoskeleton
o 3. The Hemocoel
o 4. Metamorphosis
http://www.backyardnature.net/arthropd.htm
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Segmentation, most evident externally
Each external segment bears a pair of
appendages
Body cavity not divided internally
Permits the specialization of regions of the
body for specific functions
Regional specialization = Tagmatization
o Body regions (tagmata) specialized for: feeding,
sensory perception, locomotion, visceral
functions.
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External, jointed skeleton which encloses arthropods
Provides support, protection, and prevents water loss
System of levers for muscle attachment and movement
Secreted by epidermal cells
o Epidermis covered by exoskeleton on outside
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Consists of two layers:
o 1. Epicuticle = outermost, waxy lipoprotein layer
o 2. Procuticle/Endocuticle = bulky inner layer made of chitin
 Hardening
of the
procuticle provides
armor-like protection
 Modifications of the
exoskeleton
o Formation of joints
o Sensory receptors
(bristles, lenses, etc)
o Gas exchange
 Must
be periodically
shed for growth
(ecdysis)
 Epicuticle
and Procuticle:
epicuticle
exocuticle
procuticle
endocuticle
epidermis
 Provides
an internal
cavity for the open
circulatory system of
arthropods
 Allows for the
exchange of nutrients,
wastes, and
(sometimes) gases
 Indirect
metamorphosis a
significant change in
physiology as the
immature form
becomes an adult
 Reduces competition
between adults and
immature stages
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Evolution of arthropods has resulted in an increasing
divergence of body forms, behaviors, and habitats between
immature and adult stages.
o Ex: Larval crabs feed on plankton, adult crabs prowl sandy bottoms
for live prey.
o Ex: Caterpillar feeds on leafy vegetables, adult butterfly feeds on
nectar from flowers.
Indirect
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Subphylum Trilobitomorpha- Trilobites (extinct)
Subphylum Chelicerata
o Class Merostomata- Horseshoe Crabs, giant water scorpions (extinct)
o Class Arachnida
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Order Scorpionida- scorpions
Order Araneae- spiders
Order Opiliones- harvestmen (daddy longlegs)
Order Acarina- ticks and mites
o Class Pycnogonida- sea spiders
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Subphylum Crustacea
o Class Malacostraca- crabs, lobsters, crayfish, shrimp, krill, isopods
o Class Branchiopoda- fairy shrimp, brine shrimp, and water fleas
o Class Maxillopoda- barnacles and copepods
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Subphylum Hexapoda- insects and relatives
Subphylum Myriapoda- millipedes and centipedes
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Examples: Spiders, mites, ticks,
scorpions, sea spiders
Characteristics:
o Have 2 tagmata- prosoma
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(cephalothorax) and opisthosoma
No antenna
First pair of appendages are
chelicerae-often pincer-like (chelate)
and used for feeding (may be hollow
fangs)
Second pair are pedipalps-usually
sensory or used in locomotion,
feeding, or reproduction
Paired walking legs follow
Opisthosoma contains digestive,
reproductive, excretory and respiratory
organs
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Class Arachnida
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http://healthlineinfo.com/mite-allergy.html
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Examples:
o Crayfish, crabs, lobster, shrimp, barnacles and copepods.
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Two unique characteristics:
o 1. Two pairs of antennae
o 2. Biramous appendages
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Five classes of crustaceans and numerous orders
o Class Malacostraca**
o Class Maxillopoda**
o Class Branchiopoda
o Class Remipedia
o Class Cephalocarida
 “Hard
Shelled”
 Largest class of crustaceans:
o crabs, lobsters, crayfish, shrimp, krill, isopods
 Body
divided into two regions
o 1. Cephalothorax (fusion of sensory/feeding and
locomotion tagmata)
o 2. Abdomen (a muscular tail)
http://news.sciencemag.org/sciencen
ow/2012/06/mantis-shrimpsmash.html
Paired, biramous appendages in both body regions
 Appendages on Cephalothorax:
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o Pairs 1 and 2 – Antennae (TWO pairs!)
o Pairs 3 through 5 – Mouth appendages
• Mandible Pair (Chewing)
• Maxillae (Food handling)
o Pairs 6 through 8 – Maxillipeds
• Accessory sensory and food handling appendages
o Pairs 9 through 13 – Pereopods (Walking legs)
• Cheliped (Pincher-like)
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Appendages on Abdomen
o Pleopods (Swimmerets)
o Telson used in swimming and escape responses
Paired appendages that can be seen include the
antennules (1), antennae (2), mandibles (3) that
are used to chew and crush food, one of the
second maxillae (4) that along with the first
maxillae (covered by these structures) are
involved in food handling, the flagella-like tips of
the first maxillipeds (5), most of which are
covered by the carapace, one of the second
maxillipeds (6), the third maxillipeds (7) and the
first pair of walking legs, which are called
chelipeds (8). Also seen on the image are the
openings to the green glands (9) that have been
opened with a probe to make them more visible.
Name
Region
Function
Comments
Other names used
Antennule
head
sensory
1st antennae
Antennae
head
sensory
2nd antennae
Mandible
head
crushing or grinding food items
jaw
Maxillae
head
chewing and shredding food items
1 or 2 pairs
Maxilliped
thorax
manipulating food items
3 pairs
Pereopod
thorax
walking, clinging
as many as 5
pairs
walking legs
Pleopod
abdomen
respiration, swimming, holding offspring
As many as 5
pairs
swimmerettes
Uropod
telson (last abd. segment)
swimming, escape
acessory jaws
tail fan
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Reproduction
All crustaceans are
dioecious
Mating occurs after molting
of the female
In females, developing eggs
attach to pleopods and are
brooded until hatched
In males, pleopods are
modified into claspers and
used for sperm transfer
Crayfish have direct
development
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Feeding
Predators, herbivores,
scavengers
Foregut includes an
enlarged stomach,
specialized for grinding
Midgut = “intestine”
Short hindgut ends in
anus and used for water
and salt regulation
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GillsExchange
in gill chamber
Gas
& Circulation
o Between the carapace and
body wall
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Muscular Heart
Dorsal, anterior, and
posterior arteries empty
into sinuses of hemocoel
Sensory & Regulation
 Ventral nervous system
 Compound eyes
 Crayfish: Excretion organs
are called “green glands”
 Other crustaceans:
maxillary glands
 Includes
Barnacles and
Copepods
 Copepods are most
abundant crustacean
o Marine and Freshwater
 Barnacles
are sessile
o Marine only
o Most monoecious
o Attach to various
substrates
o Some are parasitic