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Kingdom Animalia Subkingdom Eumetazoa Bilateria Phylum Arthropoda Professor Andrea Garrison Biology 3A Illustrations ©2014 Cengage Learning unless otherwise noted Phylum Arthropoda • Insects, spiders, crabs, millipedes, centipedes, etc. (arthron = joint; podos = foot) • Largest animal phylum (>3/4 all species) • All habitats • Triploblastic • Protostomes • Bilateral w/cephalization – Sensory structures • Antennae, compound and/or simple eyes, sensory hairs, auditory organs, statocysts Ecdysozoa; photo http://www.cdc.gov/dpdx/trichinellosis/ 2 Hard Exoskeleton • Chitin w/varying amounts of calcium carbonate • Muscles attached to inside of exoskeleton • Molt to grow – Develop soft exoskeleton under the old exoskeleton – Shed old exoskeleton – Aquatic • Swell with water, then exoskeleton hardens – Terrestrial • Swell with air then exoskeleton hardens – Vulnerable to predators until new exoskeleton hardens Arthropoda; photo by A. Garrison 3 Segmented Body • External joints allow movement • Tagmosis – Segments fused or grouped together in body regions • May be covered by carapace so you don’t see segments (can count appendages) – Segments within a region are similar – Segments differ between regions • 1 pair appendages/segment • Appendages may vary in function – Feeding, defense, walking, swimming Arthropoda 4 Body Regions • Head – Brain – Sensory structures • Eyes (compound or simple) • Touch, chemical, hearing – Feeding appendages • Thorax – Walking or swimming appendages – Some with wings • Abdomen – May or may not have appendages Fir0002/Flagstaffotos Arthropoda; top photo by Didier Descouens; ,://creativecommons.org/licenses/by-sa/3.0/deed.en’ bottom photo by Fir0002/Flagstaffotos 5 Body Regions • Some body regions may be fused – Cephalothorax • Head and thorax fused – Abdomen Arthropoda 6 Phylum Arthropoda • Coelomate • Complete digestive system – Head appendages modified as mouthparts • Open circulatory system – Hemocoel fills with hemolymph • 2 ventral nerve cords with ganglia – Attached to nerve ring around mouth w/ “brain” Arthropoda 7 Phylum Arthropoda • Respiratory system – Aquatic • Gills – Terrestrial • Book lungs • Trachea • Excretory system – Aquatic • Paired glands at base of antennae – Terrestrial • Malphigian tubules joined to gut • Reproductive system – Dioecious – Internal fertilization – Several stages of development between molts • Successive stages may be similar or abruptly different Arthropoda 8 Phylum Arthropoda • 5 subphyla – Trilobita – Chelicerata – Crustacea – Myriapoda – Hexapoda Arthropoda 9 Subphylum Trilobita • • • Trilobites (tri = three; lobos = lobe) All extinct Lots of fossils – Arthropods first organisms with hard parts, molt several exoskeletons • 3 lobes of body – 1 median lobe, 2 lateral lobes • • • Dorsoventrally flattened Heavy exoskeleton 3 body regions – Head • • sensory antennae compound eyes – Thorax w/appendages – Abdomen w/appendages – Appendages on thorax and abdomen all similar Arthropoda 10 Subphylum Chelicerata • Horseshoe crabs, spiders, scorpions, mites, ticks (chela = claw; keras = horn) • Marine, freshwater, few terrestrial • Predators or parasites • Cephalothorax – 6 pr appendages • 1 pr chelicerae—pincers to assist in feeding • 1 pr pedipalps—grasping, sensory, walking (pincers in scorpion to right) • 4 pr walking legs • Abdomen – May have appendages Arthropoda 11 Subphylum Chelicerata • Class Merostomata – Horseshoe crabs – Very ancient, primitive group – Nocturnal feeder • Worms, molluscs – Compound and simple eyes – Carapace covers cephalothorax • 1 pr chelicerae • 5 pr walking legs – Abdomen • 6 pr swimming appendages • Book gills – Telson Arthropoda 12 Subphylum Chelicerata • Class Arachnida – Spiders, scorpions, mites, ticks – Cephalothorax • Simple eyes may be image forming • 1 pr chelicera • 1 pr pedipalps • 4 pr walking legs – Abdomen • No appendages – Spinnerets exception to this Arthropoda 13 Subphylum Chelicerata, Arachnida • Spiders – Active hunters or spin webs to capture prey • Spinnerets on abdomen • Liquid silk hardens on contact with air • Mites – – – – – Tiny Cephalothorax and abdomen fused Agricultural pests Mange Dust mites cause allergies • Ticks – Blood-sucking ectoparasites – Cephalothorax and abdomen fused – Transmit bacterial pathogens • Rocky Mountain spotted fever • Lyme disease Arthropoda 14 Subphylum Crustacea • Shrimps, lobsters, crabs (crusta = crust, hard shell) • Marine, freshwater, very few terrestrial • Most with cephalothorax and abdomen, but some with all three body regions • Tagmosis well developed – Different regions with different functions and different appendages related to function • Walking vs swimming Arthropoda 15 Subphylum Crustacea • Cephalothorax – Often covered by carapace – 5 pr appendages on head • 2 pr antennae • 3 pr mouthparts – 1 pr mandibles » Bite, chew – 2 pr maxillae » Pass food to mouth – More appendages on thorax and abdomen • Decapods – 5 pr legs on thorax Arthropoda 16 Subphylum Crustacea • Well-developed nervous system – Large ganglia – Antennae with chemical and touch receptors – Compound eyes – Statocysts on head – sensory hairs in exoskeleton • Respiration – Gills under carapace • Excretion • Antennal gland Arthropoda 17 Subphylum Myriapoda • Centipedes and millipedes (myrias = ten thousand; pod- = feet) • Terrestrial – Under rocks, leaves • 2 body regions – Head • 1 pr antennae – Segmented trunk • Centipedes – 1 pr walking legs/trunk segment – Predators • Invertebrates and small vertebrates • Powerful toxins • Millipedes – 2 pr walking legs/trunk segment – Feed on decaying leaves, organic matter in soil Arthropoda 18 Subphylum Hexapoda • Insects (hex = six; pod- = feet) • Most successful animal group – Every habitat – Wings • Cross environmental barriers, disperse – Wingless groups • not as successful as winged groups Arthropoda 19 Subphylum Hexapoda • 3 body regions – Head • 1 pr compund eyes • 2-3 simple eyes (ocelli) • Mouthparts – – – – 1 pr antennae 1 pr mandibles 1 pr maxillae 1 labium & 1 labrum cover mouthparts – Mouthparts vary with feeding style of insect – Thorax • 3 pr legs • 2 pr wings in most – Abdomen • No walking legs • Appendages for copulation Arthropoda 20 Subphylum Hexapoda • Respiration via tracheal system – Spiracles open into system – Tracheal tubes extend to tissues • Excretion via Malphigian tubules – Carry nitrogenous wastes to intestine to be released with feces Arthropoda 21 Insect Development and Ecdysis • Developmental stages beyond the egg called instars • 3 types of development – No metamorphosis • All instars look like mini-adults – Incomplete metamorphosis • Only minor differences with each instar • Early nymphs lack wings – Complete metamorphosis • Drastic changes with each instar Arthropoda 22 Insect Development and Ecdysis Arthropoda 23 Insect Development and Ecdysis Arthropoda 24 Insect Development and Ecdysis Arthropoda 25