Phylum Arthropoda Crustaceans, Insects, Arachnids

Phylum Arthropoda – “Jointed Legs ” General Characteristics –Jointed appendages (legs, maxillipeds, antenna) –Chitinous exoskeleton Advantages: protection and muscle attachments Disadvantages: heavy, limits mobility (slow), molt (shed) in order to grow –Open Circulatory System – not as efficient as closed system. The blood is pumped from the heart out to the tissues where it “washes” over them, then eventually flows back to the heart

–Well developed nervous system Brain and ventral nerve cord Compound eyes (multiple lenses) and some have simple eyes (one lens) Hairs for touch, balance organs in the antenna, chemoreceptors (smell / taste) –Endocrine System Hormones control molting and reproduction

Major Types of Arthropods Subphylum Uniramia – Body in three parts (Head, Thorax, Abdomen) –Class Insecta – Largest class (most species) of arthropods (ants, bees, beetles, etc.) Three pairs of legs and two antenna –Class Chilopoda – Centipedes, one pair of legs per segment, usually carnivores –Class Diplopoda – Millipedes, two pairs of legs per segment, usually herbivores

Subphylum Chelicerata – body in two parts (cephalothorax, abdomen), no antennae –Class Arachnida – four pairs of legs (spiders, mites, ticks, and scorpions) –Class Pycnogonida – Sea Spiders –Class Merostomata – Horseshoe Crabs Only living members of their class (living fossil) More closely related to spiders than to crabs Contain “Book Lungs” – gills that are arranged in flaps like pages of a book that are covered so they can exit the water to reproduce

Subphylum Crustacea –Class Branchiopoda – primitive, gills on their feet (ex. Daphnia) –Class Copepeda – small crustaceans (ex. Copepods, “plankton” from spongebob) –Class Cirripeda – sessile, shelled, legs kick in the water to capture food (ex. Barnacles) –Class Malacostraca – 75% of all crustaceans are in this class Order Euphausiacea – Krill (shrimp-like) Order Decapoda – 10 walking legs, cephalothorax and abdomen –Crabs, shrimp, lobsters, crayfish