Arthropoda 5 major lines of arthropod evolution: Trilobitamorpha Cheliceriformes a. Merostomata b. Arachnida Crustacea Hexapoda a. Entognatha b. Insecta 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