Arthropods

Arthropods are what kind of protosomes?

Ecdysozoan protosome bilaterians

What group are they a part of?

Panarthropoda

What does Panarthropoda include? (subphyla)

Onychophorans (velvet worms)

Tardigrades

Arthropods

What are the living arthropod subphyla?

Chelicerata

Myriapoda

Crustacea

Hexapoda

Arthropod Appendages and Mouthparts

Appendages:

• Uniramous

• Biramous

Mouthparts:

• Chelicerae

• Mandibles

Homology of Chelicerae & Mandibles

Not the same thing

Expression of homeobox genes shows chelicerate arthropods retain their deutocerebral segment

Arthropod Features

• Found in all habitats

• Exoskeleton

• Jointed appendages

• Segmented Body

• Tagmata (distinct regions of segments)

• Triploblastic

• Eucoelmate (hemocoel/reduced coelom)

• Well dev Nervous sys and sense organs

• Dioecious

• Malpighian Tubes (terrestrial); excretory glands (aquatic)

• Gills; body surface; book lungs; trachea

  • Open circulatory system

Extinct Subphylum - Trilobita

• paleozoic (545-245 mya)

• Very diverse and abundant

• Bottom feeders

• 3-lobed body

• 3 tagmata

  • head

  • thorac

  • pygidium

• Compound eyes

Classes in Subphylum Chelicerata

• Class Pycnogonida

• Class Merostomata

• Class Arachnida

Subphylum Chelicerata Defining features:

6 pairs of free appendages

• 1 pair of chelicerae

• 1 pair of pedipalps

  • 4 pairs of walking legs

Class Merostomata

Common name: Horseshoe Crabs

• Living fossils

• Feed on worms and Molluscs

• Common in eastern US.

Class Arachnida: Spiders

Spiders (order Araneae)

• Tagmata:

  • Prosoma (cephalothorax)

  • Opisthosoma (abdomen)

• Chelicerae have fangs with poison

• predaceous

• most have silk glands

• 8 simple eyes

Class Arachnida: common names

Common names: Spiders, scorpions, ticks, and mites

Class Arachnida: Scorpions

order Scorpiones

• Nocturnal predators

• Tagmata:

  • Cephalothorax

  • Preabdomen

  • Postabdomen

• Pedipalps enlarged

• String

Harvestmen (Order Opiliones)

Class Arachnida: Ticks and Mites

Order Acari

• Cephalothorax and abdomen fused

• Mouthparts on capitulum

• Free-living or parasitic on plants and animals

• Important disease vectors in humans (Lyme disease, Rocky Mountain Spotted Fever)

Subphylum Myriapoda: Classes

Class Diplopoda (millipedes)

Class Chilopoda (Centipedes)

Subphylum Myriapoda: Features

• 2 tagmata

  • Head

  • Trunk

• Many legs

• Trachea for respiration

Myriapoda: Class Chilopoda

Centipedes

• flattened body

• One leg per segment

• poisonous

• predators

Myriapoda: Class Diplopoda

Millipedes

• herbivorous

• 2 legs per segment

• cylindrical body

• repugnatorial glands

Subphylum Crustacea Basics

Diverse

• marine, freshwater and terrestrial

  • most familar animals belong to Class Malacostraca

Crustacead Body Plan: External

• biramous appendages

  • 2 pairs of antennae

  • mandibles

  • 2 pairs of maxillae

  • maxillipads

  • swimmerets

  • uropod

• Rostrum

• Telson

• Tagmata:

  • Cephalothorax

  • Abdomen

Crustacead Body Plan: Internal

• Open circ sys

• dig sys with gastric mill in stomach

• excr org are antennal (green) glands

• Crayfish have direct dev

• Marine crustaceans have nauplius larval stage

• Feeding is diverese

Crustacean Classes

• Class Ostracoda

• Class Branchiopoda

• Class Copepoda

• Class Cirripedia (barnacles)

• Class Malacostraca

Class Malascostraca: orders

• Order Isopoda

• Order Amphipoda

• Order Euphausia

• Order Decapoda

Hexapod Structure

• Six Legs

• 3 tagmata:

  • Head

  • Thorax

  • Abdomen

• 1 pair of antennae

• 2 pairs of wings

Insect Structure - Head

• Compound eyes and ocelli

• Antennae of varied form

Insect - Mouthparts

• labrum

• mandibles

• maxillae w/palps

• labium w/ palps

• hypopharynx

Insect Mouthpart - Diversity in function

• Chewing

• sucking

• lapping

Insect: Internal Form and Function

• gut tube w/ gastric ceca

• open circulatory system with dorsal heart

• respiration by tracheae

• excretion by Malpighian tubules

• ventral nervous system, well developed brain

• sexual reproduction, sexes separate (dioecious)

Insect Flight

Direct flight muscles vs Indirect flight muscles

Hexapod - reproduction and Life Cycle

Mating

• spermatophores

• copulation

Development

• Ametabolous

  • egg > juvenile > adult

• Hemimetabolous

  • egg> nymphs > adult

• Holometabolous

  • egg > larva/grub/caterpillar > pupa (chrysalis) > adult (imago)

Each stage between molts is called an instar

What is this?

Hemimetabolous Nymphs

What are these?

Holometabolous Larvae

Eusociality

Honeybee Society

3 castes:

• Queen

• Drones

• Workers

Males are haploid (haplodiploidy

• “Royal Jelly” fed to larvae makes them queens

• Waggle Dance

insect products:

Shellac and silk

Insect services:

Pollination

Insect Pests

Locusts, aphids, pine beetles

Insect Parasites:

Parasitoid Wasps

Lice

Fleas

Bedbugs

Mosquitos

Insect Subphylum

Hexapoda

Classes in Subph. Hexapoda

Cl. Entognatha

Cl. Insecta

Order in Cl. Entognatha

Order Collembola - springtails

Cl. Insecta - 10 Orders