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Phylum Arthropoda :

Phylum Arthropoda :. Blueprint for Success Chapter 14 and 15. Characteristics of Arthropods. Modified segmentation – body regions specialized for specific functions ( tagmatization ). Chitinous exoskeleton used for support and protection Paired, jointed appendages

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Phylum Arthropoda :

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  1. Phylum Arthropoda: Blueprint for Success Chapter 14 and 15

  2. Characteristics of Arthropods • Modified segmentation – body regions specialized for specific functions (tagmatization). • Chitinous exoskeleton used for support and protection • Paired, jointed appendages • Growth accompanied by molting (ecdysis)

  3. Characteristics of Arthropods • Ventral nervous system • Reduced coelom • Open circulatory system where blood is released into tissue spaces (hemocoel) • Complete digestive tract • Metamorphosis often present

  4. Arthropods • Successful in almost all habitats on the earth. • Most abundant animals – Several million species identified • 30 to 50 million species may yet be undescribed • Triploblastic, protostome development • Exhibit bilateral symmetry • Four aspects contribute to arthropod success. • 1. Metamerism • 2. Exoskeleton • 3. The Hemocoel • 4. Metamorphosis

  5. Metamerism • Segmentation, most evident externally • Each external segment bears a pair of appendages • Body cavity not divided internally • Permits the specialization of regions of the body for specific functions • Regional specialization = Tagmatization • Body regions (tagmata) specialized for: feeding, sensory perception, locomotion, visceral functions.

  6. The Exoskeleton • External, jointed skeleton which encloses arthropods • Provides support, protection, and prevents water loss • System of levers for muscle attachment and movement • Secreted by epidermal cells • Epidermis covered by exoskeleton on outside • Consists of two layers: • 1. Epicuticle = outermost, waxy lipoprotein layer • 2. Procuticle/Endocuticle = bulky inner layer made of chitin

  7. The Exoskeleton • Hardening of the procuticle provides armor-like protection • Modifications of the exoskeleton • Formation of joints • Sensory receptors (bristles, lenses, etc) • Gas exchange • Must be periodically shed for growth (ecdysis)

  8. The Exoskeleton • Epicuticle and Procuticle: epicuticle exocuticle procuticle endocuticle epidermis

  9. The Hemocoel • Provides an internal cavity for the open circulatory system of arthropods • Allows for the exchange of nutrients, wastes, and (sometimes) gases

  10. Metamorphosis • Indirect development, a significant change in physiology as the immature form becomes an adult • Reduces competition between adults and immature stages

  11. Metamorphosis • Evolution of arthropods has resulted in an increasing divergence of body forms, behaviors, and habitats between immature and adult stages. • Ex: Larval crabs feed on plankton, adult crabs prowl sandy bottoms for live prey. • Ex: Caterpillar feeds on leafy vegetables, adult butterfly feeds on nectar from flowers.

  12. Subphylum Crustacea • Examples: • Crayfish, crabs, lobster, shrimp, barnacles and copepods. • Two unique characteristics: • 1. Two pairs of antennae • 2. Biramous appendages • Five classes of crustaceans and numerous orders • Class Malacostraca** • Class Maxillopoda** • Class Branchiopoda • Class Remipedia • Class Cephalocarida

  13. Class Malacostraca • “Soft Shell” • Largest class of crustaceans: • crabs, lobsters, crayfish, shrimp, krill, isopods • Body divided into two regions • 1. Cephalothorax (fusion of sensory/feeding and locomotion tagmata) • 2. Abdomen (a muscular tail)

  14. Class Malacostraca • Paired, biramous appendages in both body regions • Appendages on Cephalothorax: • Pairs 1 and 2 – Antennae (TWO pairs!) • Pairs 3 through 5 – Mouth appendages • Mandible Pair (Chewing) • Maxillae (Food handling) • Pairs 6 through 8 – Maxillipeds • Accessory sensory and food handling appendages • Pairs 9 through 13 – Pereopods (Walking legs) • Cheliped (Pincher-like) • Appendages on Abdomen • Pleopods (Swimmerets) • Telson used

  15. Class Malacostraca

  16. Class Malacostraca Reproduction • All crustaceans are dioecious • Mating occurs after molting of the female • In females, developing eggs attach to pleopods and are brooded until hatached • In males, pleopods are modified into claspers and used for sperm transfer • Crayfish have direct development

  17. Class Malacostraca Feeding Predators, herbivores, scavengers Foregut includes an enlarged stomach, specialized for grinding Midgut = “intestine” Short hindgut ends in anus and used for water and salt regulation

  18. Class Malacostraca Gas Exchange & Circulation Sensory & Regulation Ventral nervous system Compound eyes Crayfish: Excretion organs are called “green glands” Other crustaceans: maxillary glands • Gills in gill chamber • Between the carapace and body wall • Muscular Heart • Dorsal, anterior, and posterior arteries empty into sinuses of hemocoel

  19. Class Maxillopoda • Includes Barnacles and Copepods • Copepods are most abundant crustacean • Marine and Freshwater • Barnacles are sessile • Marine only • Most monoecious • Attach to various substrates • Some are parasitic

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