Arthropoda

5 major lines of arthropod evolution:1. Trilobitamorpha2. Cheliceriformes

a. Merostomatab. Arachnida

3. Crustacea4. Hexapoda

a. Entognathab. Insecta

5. Myriapoda

Class Crustacea

Crustacea

• 2 pairs of antennae

• Nauplius larvae

• 45,000 spp

• 6 subclasses– subC Malacostraca – decapods, amphipods, isopods (60%)– subC Brachiopoda – daphnia, brine shrimp, fairy shrimp– subC Ostracoda – ostracods– subC Copepoda – copepods– subC Pentastomida – tongue worms (nose parasites)– subC Cirripedia - barnacles

SubClass Malacostraca

• Head and thorax fused into cephalothorax

• Biramous appendages• Of huge economic imptce

– O. Decapoda: lobster, crab– O. Euphausiacea: krill

(99M tonnes in antarctica=world harvest of all other marine life combined)

krill

subC Branchiopoda

• “gill foot”

• O. Cladocera = Daphnia– Major component of FW plankton– Diel vertical migrations– Parthenogenic, ephippia, cyclomorphic,

• O. Anostraca= fairy shrimp, brine shrimp

ephippia

subC Ostracoda

• Look like small clams that actively swim

• Head encased in bivalve carapace

• Very common in FW, but also marine and some are terrestrial

subC Copepoda

• Major component of plankton in both marine and FW habitats

• Single eye “Cyclops”

• Pair of egg sacs trail behind

• Parthenogenic

• Most important herbivores in the ocean

• About 25% are parasitic

subC Pentastomida

• All tongue worms are internal parasites of the respiratory passages of vertebrates (reptiles mostly)

• Yet fossil record predates vertebrates!• Often have intermediate hosts• Ingested by final host and migrate to the

respiratory tract• Position within Arthropoda (and

Crustacea) a recent consensus

subC Cirripedia

• = hairy feet (used for filter feeding)

• Sedentary, secrete calcareous shell

• Initially classified as molluscs (have tissues analogous to a mantle, mantle cavity)

• O. Thoracica = the barnacles

• Some cirripeds in other orders are parasitic