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Arthropod

Arthropod. Phylogeny of Arthropods. Arthropoda. Annelids (worms). Onychophorans (worms w/legs). Chelicerates (spiders). Crustaceans (lobsters). Insects (butterflies). Trilobites (extinct). Worm-like Ancestor. General Characteristics metamerism (segmented body)

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Arthropod

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  1. Arthropod

  2. Phylogeny of Arthropods Arthropoda Annelids (worms) Onychophorans (worms w/legs) Chelicerates (spiders) Crustaceans (lobsters) Insects (butterflies) Trilobites (extinct) Worm-like Ancestor

  3. General Characteristics • metamerism (segmented body) • jointed appendages • bilateral symmetry • secreted exoskeleton • ecdysis (molting) • open circulatory system • ventral nerve cord and brain

  4. DIVERSITY • Numbers • about 80% of all animals are arthropods • estimated to be over 30 million arthropods • far more of them than all other metazoan species combined • in virtually every conceivable environment: • marine, terrestrial, freshwater, and aerial habitats. Phylum Arthropoda Subphylum Trilobita (extinct) Subphylum Chelicerata Subphylum Crustacea Subphylum Uniramia (insects)

  5. Phylum Arthropoda Subphylum Trilobita (extinct) Subphylum Chelicerata Subphylum Crustacea Subphylum Uniramia (insects)

  6. NERVOUS SYSTEM

  7. Open Circulatory System • Doral heart surrounded by pericardial sinus • Blood (hemolymph) enters heart through ostia (openings) pumped through arteries • Hemolymph- colorless; contains hemocyanin • Hemocoel- blood cavity

  8. Open Circulatory System

  9. Compound Eye Lens Crystalline cone Pigment cells Facet Visual cells Nerve fibers from visual cells Optic nerve Ommatidia

  10. REPRODUCTION • 1. General • most arthropods are gonochoric • fertilization may be external or internal in aquatic arthropods • always internal in terrestrial species • 2. Sperm Transfer • sperm transfer usually by mating or copulation • females usually store the sperm in a seminal receptacle

  11. Subphylum Trilobita 521-250 mya Earliest arthropod

  12. Trilobite eye

  13. Subphylum Chelicerata • xiphosurans (horseshoe crabs), arachnids, sea spiders • mostly terrestrial • cephalothorax-abdomen • 6 pairs cephalothoracic appendages • chelicerae, pedipalps, 4 pairs legs • no antennae

  14. Subphylum Chelicerata • a. Xiphosura (horseshoe crab, Limulus polyphemus) • b. Arachnida • most chelicerates are arachnids • several taxa (orders), many are common and familiar • SCORPIONES (scorpions ) • ARANAE (spiders ) • OPILIONES (harvestmen, daddy longlegs ) • PSEUDOSCORPIONES (pseudoscorpions) • ACARINI (mites and ticks ) • c. Pycnogonida (the giant sea spider, • Colossendeis australis)

  15. Limulus is a benthic scavenger and predator. • Prey include clams and other invertebrates that it digs for in the sand. • The tail spine is used as a self-righting mechanism if the animal is overturned accidentally. Lives up to 19 years • Reaches sexual maturity at about 9 to 12 years old Horseshoe Crab Limulus polyphemus, Carcinoscorpius rotunda, and Tachypleus gigas.

  16. Horseshoe Crab • Mates during spring and summer full and new moons, onto ocean beaches. • Females lay up to 30 thousand eggs, which males fertilize before burying them in the sand

  17. Horseshoe Crab

  18. Horseshoe Crab

  19. Arachnid

  20. Subphylum Crustacea • a heterogeneous taxon with many subtaxa • two pairs antennae • marine, freshwater, and terrestrial • Primarily aquatic • Free-floating larval stage • 26,000+ known species

  21. Subphylum Crustacea • ANOSTRACA • fairy shrimp and brine shrimp • PHYLLOPODA • tadpole shrimps, ostracod, water fleas • MALACOSTRACA • the largest, most heterogeneous, and diverse crustacean taxon • shrimps, crabs, lobsters, mantis shrimps, pillbugs, crayfishes • COPEPODA • copepods • enormous ecological importance as planktonic herbivores • CIRRIPEDIA • barnacles

  22. Arthropod Development Zoea Nauplius Megalops

  23. Respiration • Gills • a. General • gills are evaginations • typical of aquatic animals • blood is oxygenated by gills • oxygen delivered to tissues by blood • b. Crustacean Gills • crustacean gills are usually associated with appendages • blood circulates through the gill and is oxygenated • c. Book Lungs • present in many arachnid orders • similar to book gills of horseshoe crabs • oxygen transport from the lungs to the tissues is by blood

  24. Subphylum Uniramia

  25. Symbiosis

  26. Camouflage Decorator Crab Sponge crab

  27. Camouflage: anemone crab

  28. coral guard crabs and pocilloporid corals

  29. gall crabs and pocilloporid corals

  30. scarlet cleaner shrimp

  31. sea cucumber crab and sea cucumbers

  32. pompom crabs and sea anemones

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