The Arthropods: Blueprint for Success

Taxonomy we will cover in this Phylum:• Subphylum Crustacea

•Class Malacostraca• Exp. Lobster

•Class Cirripedia• Exp. Barnacles

• Subphylum Chelicerata•Class Merostomata

• Exp. Horseshoe crab•Class Arachnida

• Exp. Spiders

General Facts• Over a million species• Between 70-85% of all named species on Earth are Arthropods.

•The majority being insects!• Live on land, oceans, & freshwater.• Range in size from 12 ft. armspan (King Crab) to microscopic insects & crustaceans & range in taste

King Crab!

Horseshoe CrabFind mates in water

Go to beach & mate (leave sea briefly) and lay eggs

Eggs develop on land

Spotted Cleaner Shrimp

Pumpkin Spider

Giant Weta

Peruvian Giant Centipede

Millipede

6 Key Features to Arthropod Success:

1. Metamerism2. Exoskeleton 3. Jointed Appendages4. Efficient Respiratory System5. Sensory Structures6. Complex Behaviors

Arthropod Success- A group of animals with a proper toolkit to dominate.Metamerism – segments are grouped into body

regions; allows for specialization. • Tagmata - specialized for feeding and sensory perception, locomotion, and visceral functions. (segments fused together)

Exoskeleton – skeleton outside body. Protection (body armor), support, H2O retention, muscle attachment

• Ecdysis (molting) – emerges with entire new covering (soft at first..then hardens over 2 days)

Jointed appendages – adapted for a variety of functions - imagine yourself w/out joints.

Success continued… Efficient Respiratory System – tracheal system of tubes throughout the body with tiny openings (spiracles) that open into the trachea – tubes

• Allows for direct access of oxygen to muscles

More Developed Sensory Structures – allow organisms to be more aware

• Compound eyes, antennae, etc.

Complex Behaviors – no big development in nervous system; but migrates every year, social behavior, can learn

• Allows better survival and more generations

• Each leg has tremendous flexibility• Saltatorial, cursorial, etc.

• Muscles can attach to exoskeleton• Legs and body segments = potential to adapt & evolve

MetamorphosisPhysical change over time; one body form to another

• Complete (holometabolous) (indirect)• Egg Larva Pupa Adult• Larva & Pupa do not look like adult

• Incomplete (hemimetabolous) (direct)• Egg Nymph (instars) Adult• Instars look like mini adults

Incomplete (hemimetabolism) (Direct)

Complete (holometabolism) (indirect)

EXTINCT ARTHTROPOD • Trilobites!

• Dominant form of life in the oceans during the Cambrian period.

• Body oval, flattened & divided into 3 sections, had eyes, could walk & swim, roll in a ball for protection.

Subphylum Crustacea• Crayfish, shrimp, lobster, crabs, copepods, isopods.• 2 pairs of antennae, bi-ramous appendages.

Class MalacostracaOrder Decapoda

• Shrimp, crayfish, lobster, crabs.• Have a cephalothorax and abdomen.• They eat anything!• Gills are in the carapace between body wall.• Sensory structures: antennae, compound eyes, simple eyes, statocysts, chemoreceptors, proprioceptors, tactile setae.

Exoskeleton (molted)• Draw & label a crayfish – antennae, antennules, cephalothorax, abdomen, uropod, telson, swimmerets, walking legs, cheliped, rostrum, carapace, eye

Order Decapoda• Isopods (pill bugs) are common under rocks and in leaf litter.• Copepods are the most abundant.

Subphylum CrustaceaClass Cirripedia

• Barnacles• Unique because they are sessile (attached to a substrate).

Barnacle Life Cycle

Direct or Indirect?

Subphylum ChelicerataIncludes the horseshoe crabs, sea spiders, spiders, mites, & ticks.

Chelicerata Characteristics2 tagmata - cephalothorax & abdomen

Mandible – jaw for chewing

Chelicerea - (used for feeding)

• Located on cephalothorax

• Pedipalps - (sensory or feeding)

• Located on cephalothorax.

Subphylum ChelicerataClass Merostomata

• Includes horseshoe crabs and the giant water scorpion (extinct).

• Horseshoe crabs have remained virtually unchanged for 200 million years.

• They have a long tail-like extension (telson) that helps it flip over.

• Dioecious – lay eggs in intertidal areas.

Subphylum ChelicerataClass Arachnida

• Spiders, ticks, mites, scorpions.• Most are carnivorous – they use chelicerae to hold food while injecting it with digestive enzymes & suck out the tissue.

Subphylum ChelicerataClass Arachnida

continued…• Either have book lungs (folds in the body wall that allow gas exchange) or • tracheae (tubule system- opens to the outside through spiracles & allow oxygen directly into body tissue

Arachnid Development• Direct life cycle– young hatch as mini adults. (Hemimetabolism)

Arachnids Impact Humans• Humans have been impacted the most by Acarines (ticks & mites).• Can transmit disease and cause irritation.

Subphylum MyriapodaClass Chilopoda vs. Class

Diplopoda• centipedes vs. millipedes• Fast moving vs. slow moving

Subphylum HexapodaClass Insecta

Entomology – study of insects

3 tagmata – head, thorax, & abdomen• Head region – specialized for feeding and

sensory input• Thorax – specialized for movement • Abdomen – specialized for respiration,

digestion, reproduction, etc.

Class Insecta continued..

• Many types of mouths – chewing, piercing, sucking, etc.• Silk glands – movement, create nests/webs• Pheromones – chemical substance released outside of the body and influences other organisms

• Exp. sex pheromones (beetles, attack pheromones (honeybees)

Draw and label an insect:• Include: 3 segments, compound eye, ocelli (simple eyes), mandible, labrum, antennae, thorax (pro, meso, meta) abdomen, tympanum, ovipositor (female only), leg (5 parts), jumping leg, protective wing, flight wing, spiracles