Chapter 20 Phylum Arthropoda- This phylum constitutes the largest assemblage of organism in the animal kingdom- Bilaterally symmetrical- Metameric- Chtin-protien exoskeleton which must be molted for growth- Jointed appendages- High degree of cephalization- Advanced nervous system w/compound eyes- Protostomates—undergo determinate cleavage but most have reduced schhizocoel- Open circulatory system- Complete digestive tract but highly specialized (foregut, midget, hindgut)- Respiration: aquatic species have evolved gills while most terrestrial possess tracheal systems- No not have nephridia for osmoregulation and excretion!- Most have separate sexes and internal fertilization- 5 subphyla:o Trilobitomorpha (fossil)o Chelicerata (horseshoe crabs, spiders, and sea spiders)o Crustacea (crustaceans, branchipods, copepods, barnacles)o Myrapoda (centipedes & Millipedes)o Hexapoda (insects) Subphylum Trolibitomorpha- Extinct group of primitive arthropods which were marine dwellers- 3 body part were a pair of dorsal longitudinal grooves- 3 larval stages in life cycle- protaspis, intermediate meraspis larva, adult holaspid larva  Subphylum Chelicerata- Body divided into cephalothorax (fused head and thorax)- No antennae- First appendages are for feeding- Second pair are pedipalps—modified walking legs- Have compound eyes Class Merostomata (horseshoe crabs) Class Arachnida (spiders, scorpions, ticks, mites) Order Acarina (ticks and mites) Order Araneae (spiders)  Subphylum Crustacea- Very large group of arthropods like crabs, lobsters, shrimp.- Can be separated from most other extant arthropods like insect by having a biramous appendage.- Only group that is primarily aquatic- The head has 5 pairs of appendages- Calcified cuticle- Some use predation with appendages, others filter feed- Respiration by gills- Highly developed nervous system- Most are dioecious, some hermaphroditic- Earliest stage is a nauplius larva Class Branchiopoda Generallly small, freshwater “Gill feet” most are filter feeders Order Anostraca (Fairy Shrimp)  “without carapace” stalked compoiund eyes elongated trunk with 20 segments, up to 19 w/ appendages Order Notostraca (Tadpole Shrimp) Have a large shield like carapace 70 pair of appendages on long flexible abdomen 2nd antennae reduced, compound eyes sessile  Infraclass Diplostraca Composed of laterally compressed branchiopods, enclosed in clam-likebivalve carapace Only these inhabit large streams, ponds, and lakes Swim by sweeping highly developed second antennae through water Order Cyclestherida (Clam Shrimp) Looks like a clam, body entirely enclosed in carapace that is dorsally folded 10-32 trunk segments each with pair of appendages 2nd antennae well developed Sessile compound eyes  Order Cladocera (Water Fleas) genus Daphnia Trunk is enclosed in carapace but head is not Head projects ventrally giving beak-like appearance No obvious external segmentation 5-6 trunk appendage parts  Class Ostracoda (mussel of seed shrimp) Completely enclosed in bivalve carapace More clam like than shrimp in that valves are more rounded Head makes up majority of body and trunk is reduced Trunk segmentation lacking and only 2 pair of trunk appendages Most live near or on bottom Diverse feeding habits One male and one female gonopore Eggs shed free in water  Parthenogenesis is common in some freshwater groups Class Maxillopoda Sublcass Copepoda (copepods) Lack compound eyes Most planktonic or benthic All appendgaes can be used in swimming, but 2nd antennae main one  Benthic species feed on microorganisms Freshwater species lack circulatory system Subclass Branchiura (Fish Lice) Ectoparasites on fish and some amphibians Mainly freshwater Separate from copepod bc they have a pair of sessile compound eyes and large shield-like carapace covering head and thorax Lacks segmentation Claw like attachments on first pair antennae Infraclass Cirripedia (barnacles) Only group of sessile crustaceans Exclusively marine Carapace enclosing entire body Genus Cypris Subclass Malacostraca  Largest group of crustaceans, mostly marine-crabs and lobster Freshwater ones are crab, shrimp, crayfish Fixed number of segments, all have appendages Most have gills Maxillipeds-first 1-3 pairs of thoracic appendages Pleopods on abdomen modified for swimming, gathering, brooding eggs, swimmerettes in males Order Mysidacea (Opossum Shrimp) Filter feeders Most do not have gills  Ventral marsupium for brooding young Order Isopoda (Sow Bugs i.e. roley poley) One of the largest in crustaceans Lack carapace Modified pleopods for respiratory organs  Sessile compound eyes Order Amphipoda (Scuds) Very diverse Mostly marine Laterally compressed body form and respiratory organsattached to the pereopods Females have a brood sac Compound eyes  No carapace Genus Gammarus Order Decapoda (Shrimp, crab, lobster, crayfish) Subphylum Myriapoda- Centipedes and millipedes- Unbranched appendages- Single set of antennae- Respiration by trachea and excretion carries out by Malpighian tubules Class Chiilopoda (centipedes) One pair of legs per body segment Most predacious Many venomous in tropical areas  Class Diplopoda (Millipedes) Double trunk segments each bearing two pairs of legs Simple eyes Herbivores  Subphylum Hexapoda Class Insecta 3 segmented thorax with 3 pairs of appendages Have compound and simple eyes 3 mouth parts: mandibles, maxillae, and labium Insect metamorphosis:o Ametabolous—no metamorphosiso Hemimetabolous- incompleteo Paurometabolous- gradualo Holometabolous- Complete Order Ephemeroptera (mayflies) Order Odonata (Dragonflies) Order Plecoptera (Stoneflies) Order Hemiptera (true bugs) Suborder Prosorrhyncha (water striders and stink bigs) Suborder Auchenorrhyncha (cicadas and leafhoppers) Suborder Sternorrhyncha (all aphids) Order Megaloptera (Dobsonflies & Alderflies) Order Coleoptera (Beetles) Order Diptera (Flies) Order Mantodea (mantids) Order Blattodea (cochroaches) Order Phasmida (walking sticks) Order Orthoptera (grasshoppers & crickets) Order Isuptera (Termites) Order Dermaptera (earwigs) Order Mallophaga (chewing lice) Order Anoplura (sucking lice)