Arthropoda 5 major lines of arthropod evolution: 1. Trilobitamorpha 2. Cheliceriformes a. Merostomata b. Arachnida 3. Crustacea 4. Hexapoda a. Entognatha b. Insecta 5. Myriapoda
Jan 14, 2016
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