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