Ch. 14 Notes
The Giant Prickly Stick Insect (Extatosoma tiaratum) is
found in Australia. They are herbivores who cannot bite or
sting in defense, but will take a scorpion-like stance to ward
off predators and release an odor that smells a lot like toffee
or peanut butter.
 Successful in most habitats
 First terrestrial animals
1.) Exhibit
 Metamerism (segmentation) with
 Tagmatization (specialization of body regions)
 head, thorax, abdomen
2.) Have jointed, chitinous exoskeleton; cuticle
 Chitin – a polysaccharide (similar to cellulose)
 Secreted by epidermal cells
 Protection & Support
 Ecdysis – shedding of the exoskeleton to allow for
growth; molting
3.) Undergo metamorphosis
 Change in shape/structure
 Transition of developmental stages (larva adult)
 Reduces competition for resources
 Caterpillar eats leafy
greens; butterfly eats
nectar
4). Have an open circulatory system
 Hemocoel – the cavity where blood is released from
blood vessels
 Internal organs are bathed by body fluids in the hemocoel
 provides for the exchange of nutrients, wastes, and gases
Trilobitomorpha – extinct – trilobites
1.


Marine
Cambrian-Carboniferous time period
Chelicerata – spiders, mites, ticks, horseshoe crabs,
sea spiders, scorpions
3. Crustacea – ‘hard shelled’ – crayfish, shrimp, lobster,
crabs, water fleas, barnacles
4. Myriapoda – millipedes & centipedes
5. Hexapoda – ‘six legs’ – insects & their relatives
2.
Body divided into prosoma & opithosoma
 Prosoma – ‘cephalothorax’ – a sensory,
feeding, and locomotor segment
 Contains eyes
 No antennae
 Paired appendages
 1st pair = chelicerae – pincher like; used for
feeding
 May be specialized fangs
 2nd pair = pedipalps – usually sensory,
feeding, locomotion, or reproduction
 3rd pair + so on = walking legs
 Opithosoma – Segment that contains
digestive, reproductive, excretory, and
respiratory organs
Class meristomata
1.


Horseshoe crabs
Giant sea scorpions (extinct)
Class arachnida
2.

Spiders, scorpions, ticks, mites
Class pychogonida
3.

Sea spiders
 Only 4 species of horseshoe crabs
living today
 Atlantic Ocean & Gulf of Mexico
 Body unchanged for 200 million
years
 Dioecious
 Scavenagers – eat annelids and
small molluscs
 Book gills: used for gas exchange
between blood and sea water
 Impermeable
exoskeleton to retain
water
 Mostly carnivores
 Spiders produce
webs to trap small
arthropods to eat
 All dioecious (except for
barnacles)
 Mostly aquatic (except for some
isopods & crabs)
 2 Differences that separate
crustaceans from other
arthropods
 They have 2 pairs of antennae
 They have biramous appendages
(branches into two)


The largest class of crustaceans
Common members= crayfish, shrimp, lobsters,
crabs, copepods, isopods
 Oviparis (most arthropods)
 Females lay eggs that develop outside the body
 Viviparis (Primitive arthropods)
 Eggs in female reproductive tract
 Females provide nutrients to nourish embryo
 Ovoviviparous (Many arthropods)
 Eggs develop inside reproductive tract
 Nourished by food stored in egg
 Divided into two regions
 Cephalathorax
 Fusion of a sensory & feeding
tagma (head) with a locomotor
tagma (thorax)
 Abdomen
 Posterior to the cephalathorax
 Has locomotor and visceral
functions
 1st & 2nd pair = Antennae &
Antennules
 3-5 – associated with the mouth
 3rd = mandibles –
chewing/grinding structures
 4&5 = Maxillae – food handling
 6-8 – maxillipeds – sensory &
food handling (last 2 have gills)
 9-13 – Pereopods – walking legs
(10 legs)
 9 = cheliped = pincherlike, used
for food capture
 13 = pleopods (swimmerets)
 Shrimp, water fleas
 Primarily fresh water
 Flattened, leaf-like appendages used in :
 Respiration
 Filter feeding
 Locomotion
 Barnacles
 Monoecious
 Some are parasites