Subphylum Uniramia

Subphylum Uniramia
Arthropod Characteristic Differences
Subphylum
Characteristics
Representatives
Uniramia
1 pair of antennae
uniramous legs
tracheal system =
spiracles, trachea
and trachioles
mostly terrestrial
No antennae
Fangs (chelicerae)
Pedipalps
(pinchers)
8 legs
2 pairs of
antennae
biramous legs
legs attached to
abdomen
gills
Millipedes
Chelicerata
Crustacea
Centipedes
Insects
Horseshoe crabs
Spiders
Ticks/Mites
Scorpions
Crabs
Lobsters
Shrimp
Pill bugs
Uniramia Fossil Record
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How does the Subphylum Uniramia fit
into the Arthropoda and Animalia?
Subphylum
Uniramia
Largest arthropod subphylum
Comprises 75% of all known
animals
Uniramia Characteristics
Most live on land
Incredible evolutionary adaptation
= can live where few metazoans
can (oil swamps, sulfur springs etc)
Close to 1 million insects described
(20-50 million undescribed)
Beetle family (65,000 species)
largest
Appendages multiarticulate
Body with several tagmata
Needless to say, in order to cover
everything interesting and
important you will need an entire
course = Entomology
Uniramia: Gas Exchange
by tracheal system (consists of thin-walled tubes)
tracheal tubes open to the outside by spiracles
if juveniles are aquatic, they may have gills
spiracles
Uniramia: Circulatory System
Semi-closed circulatory system consisting of tubular
hearts (with openings = ostia) and a hemocoel (main
body-cavity) filled with hemolymph (blood)
Uniramia: Digestive System
Complete digestive system (straight) with
regional specialization
cuticle
foregut
midgut
(where absorption of
nutrients takes place)
hindgut
Uniramia: Excretion
Malpighian tubules:
proctodeal evaginations
Uniramia:
Reproduction
sexual and dioecious
usually internal
fertilization
Extensive larval
development = including
several developmental
stages
Subphylum Uniramia
Class Chilopoda
aka the centipedes
active predators = some with poisons
body is slightly flattened dorsoventrally
Subphylum Uniramia
Class Chilopoda
2 tagmata:
head
trunk
Somite
1 pair of appendages on most
somites
1st somite has poison claws
Subphylum Uniramia
Class Diplopoda
millipedes
generally herbivores + detritovores
body is cylindrical
Subphylum Uniramia
2 tagmata:
head
Class Diplopoda
trunk
Somite
2 pairs of appendages
on most somites
Subphylum Uniramia
Class Insecta
Most numerous and diverse group of the arthropods
about 1 million described species, 20-50 million still undescribed.
Keys to Insect Diversity
Small size (can exploit more niches)
Short generation time (adaptation can occur
quickly)
Metamorphosis
Winged adults (dispersal)
Adaptations to terrestrial environment
(e.g. waterproof cuticle, tracheal system)
Sophisticated sensory system
Behavior and communication
Co-evolutionary interactions with other
organisms (e.g. mutualisms and parasitism)
Subphylum Uniramia
3 tagmata:
Class Insecta
has 1 pair of antennae
may have wings
thorax
abdomen
has 3 pairs of legs
may have 2 pairs
of wings
head
Class Insecta: Flight
Some insects have both
direct and indirect flight
muscles (e.g. Orthoptera,
Odonata):
indirect muscles pull body
wall down and lift wings
direct muscles pull the
wings down
direct
indirect
Class Insecta: Flight
Some insects have only
indirect flight muscles
(e.g. Diptera, Hymenoptera).
In these insects, the wings
are moved by altering the
shape of the thorax.
Class Insecta: Subclasses
Insects are separated into 2 subclasses based on
whether they undergo metamorphosis/develop wings.
Subclass Apterygota
Subclass Pterygota
- primitive insects that
do not have wings
- insects that develop
wings via 2 types of
metamorphosis
silverfish
Class Insecta
Subclass Pterygota
2 types of Metamorphosis:
Division
Exopterygota
Division
Endopterygota
Hemimetabolous
(incomplete metamorphosis)
Holometabolous
(complete metamorphosis)
Class Insecta, Subclass Pterygota
Division Exopterygota
Hemimetabolous
(incomplete metamorphosis)
5 ORDERS:
Order
Order
Order
Order
Order
Orthoptera
Isoptera
Odonata
Hemiptera
Homoptera
Class Insecta, Subclass Pterygota
Division Endopterygota
Holometabolous
(complete metamorphosis)
4 ORDERS:
Order
Order
Order
Order
Coleoptera
Lepidoptera
Hymenoptera
Diptera
Ecology
Insects are important pollinators
Many flowering plants have evolved to exploit
insects as pollinators
Extrafloral
nectaries
Sexually deceptive orchids
Many flowering plants have evolved rewards to
attract pollinators (nectar)…
Nectar guides
… and displays to advertise these rewards.
Ecology
Eusocial (truly social) insects (Hymenoptera and
Isoptera) live in societies characterized by:
• Cooperative care of young
• Overlap of generations
• Polymorphism (caste system)
Symbioses
Parasitism
Parasitic insects are usually only parasites for part of
their lives (e.g. mosquitoes). However, some insects are
parasites for their entire lives (lice).
Anopheles mosquitos
transmit malaria
Lice are ectoparasites of
most birds and mammals
Symbioses
Parasitoids
Parasitoid larvae are parasites that eventually kill
their hosts, while the adults are free-living.
Symbioses
Mutualisms
Some insects are involved in obligate mutualisms (both
partners require one another). These are often plantpollinator relationships.
Figs and fig wasps
Yucca and Yucca Moths
Behavior
Fungus gardening (leaf-cutter) ants
Collect leaves and bring
them back to nest
The ants chew up the leaves, and inoculate the
mash with enzymes from the hind gut which
allow certain types of fungus to grow. The
fungus is fed to the developing larvae.
Behavior
Honey bees are capable of communicating the
location of foraging sites to the rest of the
colony by “dancing”.
The “waggle dance”
communicates the location and
quality of distant food sources.
The “round dance” communicates
the location and quality of
nearby food sources.