Phylum Arthropoda
Subphylum Trilobita
Subphylum Chelicerata
Taxonomy
• Phylum Arthropoda
– Subphylum Trilobita (Extinct)
– Subphylum Chelicerata
• Class Merostomata (Horseshoe Crabs)
• Class Arachnida (Spiders, scorpions, and mites)
• Class Pycnogonida (Sea Spiders)
– Subphylum Crustacea
– Subphylum Uniramia
• Class Chilopoda
• Class Diplopoda
• Class Insecta
General Characteristics
• Arthropods have an exoskeleton made up
of chitin- a polysaccharide attached to
protein.
• Arthropods („joint foot‟) have jointed
appendages.
• Body is constructed of serially repeated
segments (metamerism)
• Tagmatization- fusion and specialization of
segments.
General Characteristics
• Triploblastic
• Eucoelomate
• Bilaterally symmetrical.
• Open circulatory system with blood-like
tissue called hemolymph.
• Arthropods must molt, or shed their
exoskeleton, in order to grow in size.
Subphylum Trilobita
• Trilobites are an extinct
group of arthropods that
dominated the oceans
before the Mesozoic era.
– Body composed of three
tagmata- head, thorax,
and abdomen
– Biramous, or two-
branched, appendages.
– All marine.
Subphylum Chelicerata
• Groups include the horseshoe crabs, sea
spiders, spiders, scorpions, mites, ticks, and
others.
• Unlike other arthropods, chelicerates do not
have mandibles used for chewing food. Their
first pair of appendages (chelicerae) are
modified for tearing food apart)
• Two tagmata- cephalothorax, and abdomen.
• No antennae.
Class Merostomata
• Horseshoe crabs
– Living fossils. Horseshoe crabs have changed little
in 425 million years!
– All marine
Class Merostomata
Class Pycnogonida
• Sea Spiders
– Predatory marine chelicerates.
– Sea spiders have almost no abdomen. The
intestines of sea spiders have long diverticula
that extend into the legs.
– Sea spiders have a long proboscis with a
terminal mouth. They feed largely on
cnidarians and other soft-bodied
invertebrates.
Class Pycnogonida
Class Pycnogonida
Class Arachnida
• Generally terrestrial with a few aquatic
types.
• Arachnids possess one pair of chelicerae,
one pair of pedipalps, and four pair of legs.
• Two tagmata- cephalothorax and
abdomen.
• Class Arachnida is composed of spiders,
scorpions, solfugids, mites, ticks, and their
kin.
Class Arachnida
http://tolweb.org/tree?group=Arachnida&contgroup=Arthropoda
Spider External Anatomy
Spider Legs
http://www.uky.edu/Agriculture/CritterFiles/casefile/spiders/anatomy/leg.png
Spider Internal Anatomy
Spinnerets
http://www.dianamarques.com/images/spinnerets.jpg
http://www.pbrc.hawaii.edu/bemf/microangela/mspigot7o.jpg
Silk
• Spiders have six
spinnerets that can
produce up to seven
different types of silk.
• Spider silk is made
of protein and is one
of the strongest
natural substances
in the world.
Silk
• Silk is produced in
liquid form, but dries
upon contact with air.
• All spiders produce
silk, but not all spiders
spin webs.
• Silk is also used for
shelter, reproduction,
and drag lines for
jumping and
“ballooning.”
Black Widow Spider (Female)
Brown Recluse Spider
Tick Mite
Scorpion
Solfugid
(A.K.A. Sun Spider, A.K.A. Camel Spider,
A.K.A. Wind Scorpion)
Pseudoscorpion