The Cambrian Explosion

The Phylum Arthropoda The most successful animal group on earth HOW DO THEY DO THAT? 1. Hard exoskeleton composed of chiton 2. Segmented body and specialized jointed appendages 3. Complex nervous & sensory system 4. Variety of respiratory organs 5. Complex innate and learned behaviors 6. Complex life cycle with metamorphosis

Segments of Arthropod Body Partitioned into Two or Three Tagmata cephalothorax abdomen cephalothorax head thorax abdomen

Arthropod Muscular System

Arthropod Respiratory Systems

Subphylum Trilobita Once abundant in ancient oceans Extinct for over 200 million years

Subphylum Chelicerata 1. Two tagmata (cephalothorax and abdomen) 2. 6 pairs of appendages: chelicerae, pedipalps, 4 pairs walking legs (no antennae, no mandibles) 3. Respiration via book gills or book lungs

Class Merostomata: Horseshoe Crabs 1. cephalothorax completely covered with a large carapace Long, spine-like telson Book gills

Class Pycnogonida: Sea Spiders 1. Four pairs of long, thin walking legs (some males have one pair modified for carrying eggs = ovigers) 2. Proboscis for sucking juices from hydroids 3. Abdomen reduced or absent

spiders, scorpions, mites, ticks Class Arachnida spiders, scorpions, mites, ticks 1. cephalothorax partially or completely covered with a carapace-like shield 2. Abdominal appendages (if present) modified into spinnerets (spiders) or pectines (scorpions)

Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

Brown Recluse Spider

Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

Multiple Pairs of Eyes Spinnerets

Class Arachnida Order Scorpionida - Scorpions Modified abdominal appendage (pectine) Order Opiliones - Harvestmen Chelicera modified into pincer-like appendages Order Acari - Ticks and Mites Mouthparts on anterior projection (capitulum) Transmit a wide variety of diseases

Subphylum Myriapoda (millipedes, centipedes) Uniramous (unbranched) appendages Paired appendages on most/all segments Body of two tagmata (head & trunk) One pair of antennae, mandibles, maxillae Respiration via tracheae and spiracles

Class Chilopoda: Centipedes one pair legs per segment appendages of 1st body segment modified to form poisonous fangs predatory

Class Diplopoda: Millipedes two pair legs per segment hatch with 3 pairs of legs herbivores or scavengers unique defensive behavior

Subphylum Crustacea Mostly marine, some freshwater Three tagmata (head, thorax, abdomen) 2 pr antennae, 1 pr mandibles, 2 pr maxillae Biramous, highly specialized appendages Respiration via gills

Biramous Specialized Appendages

Stalked Compound Eye

Simple vs. Compound Eye Compound Eye Simple Eye Camera Eye Concave Mirror Eye Pinhole Eye 1. Light enters transparent cuticle 2. Crystalline cone 3. Light sensitive cells stimulated 4. Nerve impulses fired off to brain Compound Eye

Ecdysis Have to molt to grow Under hormonal control 1. Epidermis secretes new cuticle under old cuticle 2. Dissolves and resorbs calcium to weaken the old cuticle 3. Splits old cuticle and discards 4. Absorbs water to swell body 5. Hardens new shell 6. Reestablishes osmotic balance

Crustacean Reproduction Aquatic larval stages: nauplius and zoea Molt through many intermediate larval stages Separate sexes with sexual dimorphism

Oligostraca bivalve carapace completely encloses body Ostracoda, Branchiura, Pentastomida bivalve carapace completely encloses body

Pentastomida parasite of carnivorous vertebrates Four claw-like appendages Chitinous cuticle Extensive parasitic modifications make phylogeny difficult

Branchiopoda, Copepoda, Thecostraca, Malacostraca Vericrustacea Branchiopoda, Copepoda, Thecostraca, Malacostraca

Branchiopoda Diplostraca (cladocerans), Anostraca (fairy shrimp), Notostraca (tadpole shrimp) bivalved carapace or no carapace no abdominal appendages

Malacostraca isopods, amphipods, euphausids, decapods All thoracic and most abdominal segments bear specialized appendages Gills occur along the bases of thoracic appendages

Kiwa hirsuta

Subphylum Hexapoda (entognatha, insects) Uniramous (unbranched) appendages Body of three tagmata One pair of antennae, mandibles, maxillae Respiration via tracheae and spiracles

Class Insecta: Insects Body composed of three tagmata (head, thorax, abdomen) One pair of large compound eyes and multiple ocelli One pair of antennae Three pairs of walking legs Two pairs of wings one may be reduced = halteres

Wingless insects Winged insects some species lack tracheae direct development all have tracheae metamorphic development

Insect Respiratory System Tracheoles Air sacs Tracheae Spiracles

Insect Excretory System

Insect Flight direct muscle system indirect muscle system muscles to raise wings muscles to lower wings direct muscle system longitudinal muscles dorsoventral muscles indirect muscle system

Complete metamorphosis egg  larva pupa adult

Modifications of Mouthparts mouthparts modified for piercing/sucking mouthparts modified for chewing plant material mouthparts modified for grabbing mouthparts modified into a long proboscis

Complex Behaviors nocturnal swarming

Social Systems queen worker drone

1. Subphylum Trilobitomorpha 2. Subphylum Chelicerata a. Class Merostomata - horseshoe crabs b. Class Pycnogonida - sea spiders c. Class Arachnida – spiders, scorpions, ticks, mites 3. Subphylum Crustacea Class Branchiopoda - cladocerans, brine shrimp Class Maxillopoda - ostracods, copepods, barnacles c. Class Malacostraca - isopods, shrimps, crabs, lobsters 4. Uniramia Subphylum Myriopoda a. Class Diplopoda - millipedes b. Class Chilopoda - centipedes 5. Uniramia Subphylum Hexapoda Class Insecta – insects Class Entognatha – spring tails, bristletails, proturans