Arthropods

1. Arthropods

2. http://www.iteachbio.com/Marine-Biology/Arthropods.mov

3. Arthropoda • Arthro-joint; pod-foot • Largest group of animals • Spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects, etc. • Found in all types of environment • All feeding types – • carnivorous, omnivorous, herbivorous • All arthropods have • Exoskeleton • Segmented body • Body segments grouped into specialized regions (= tagmata, plural) • Jointed legs • Air piped directly to cells • Highly developed sensory organs

4. Exoskeleton • Cuticle • Outer covering secreted by epidermis • Composed of 2 layers • Both layers contain chitin • Tough, resistant, nitrogenous polysaccharide • Procuticle • Inner, thicker part of cuticle • Exocuticle – secreted before a molt • Endocuticle – secreted after a molt • Epicuticle • Outer, thin part of cuticle • Composed of protein & lipids

5. Exoskeleton • Some arthropods grow too big for their exoskeletons & must molt • Molting (ecdysis) is to leave an exoskeleton and grow a new one

6. Segmentation • Typically each segment has a pair of jointed appendages • Limb segments • Hollow levers, rapid action • Jointed appendages • Sensory hairs for food handling, swift/efficient walking or swimming Air Piped Directly to Cells • Highly efficient tracheal systems of air tubes • Delivers oxygen directly to tissues & cells • Creates a high metabolic rate

7. General • Usually are active, energetic animals • Most abundant and diverse of all animals • Greatest diversity (have no rivals) • Most number of species • Widest ecological distribution • They compete with us for food and spread serious diseases • They are essential in pollination of many food plants • They also serve as food, yield drugs and dyes • And create products like silk, honey, and beeswax

8. Subphylum Trilobita • became extinct about 200 million years ago • they were bottom dwellers, probably scavengers • could roll up like pill bugs

9. Subphylum Chelicerata • very ancient group including: horseshoe crabs, spiders, ticks and mites, scorpions, sea spiders, and others • characterized by presence of 2 tagmata and six pairs of appendages • a pair of “chelicerae • a pair of “pedipalps” • four pairs of walking legs • they have no “mandibles” or “antennae” • most suck liquid food from their prey

10. Class Merostomata (Subphylum Chelicerata) • (horseshoe crabs) • only five living species • 12” males, 18” females • live in shallow water along North American Atlantic coast • feed at night on worms and small molluscs • are harmless to humans

11. Horseshoe Crabs

12. Horseshoe Crabs

13. Class Pycnogonida (Subphylum Chelicerata) • (sea spiders ) • Move on four pairs of long, thin walking legs • Feed by sucking juices from hydroids and soft-bodied animals • Often have a pair of ovigerous legs (ovigers) with which males carry the egg masses • Common in all oceans

16. Vent Sea Spider

17. Class Arachnidan • Over 50,000 species • Spiders, scorpions, pseudoscorpions, ticks, mites, harvestmen (daddy longlegs), etc • Tagmata • Cephalothorax & abdomen

18. Class ArachnidaOrder Araneae: Spiders • Over 35,000 species • Cephalothorax & abdomen show no external segmentation • The tagmata are joined by a narrow, waistlike “pedicel” • Predators • feeding mostly on insects • Chelicerae • function as fangs and bear ducts from their venom glands • Some chase their prey, other ambush them, and many trap them in silk webs

20. Class ArachnidaOrder Araneae: Spiders • Seizes prey with chelicerae • Injects venom • Venom liquefies tissues, allowing spider to suck the broth into the stomach • Spiders with teeth crush or chew prey

21. Class ArachnidaOrder Araneae: Spiders • Spiders breathe by book lungs or tracheae (or both) • Book lungs – many parallel air pockets extending into a blood-filled chamber

22. Class ArachnidaOrder Araneae: Spiders • Excretory System • Malpighian tubules • Works in conjunction with specialized rectal glands • Potassium, other solutes, and waste materials are secreted into the tubules, • which drain the fluid, or “urine” into the intestines • Rectal glands reabsorb most of the potassium and water • producing a nearly dry mixture of urine and feces

23. Class ArachnidaOrder Araneae: Spiders • Eight Simple Eyes (poor vision) • Each provided with a lens, optic rods, and retina • Perceive moving objects • Some may form images • Sensory setae • Hairlike structure to aid in awareness of its environment • Setae communicate information about Surroundings • Air currents, changing tensions in web

24. Class ArachnidaOrder Araneae: Spiders • Web-Spinning Habits • Silk glands • Found in 2-3 pairs of spinnerets • Emits a protein secretion as a liquid; hardens on contact with air to form a silk thread • Stronger than steel threads (same diameter) • Silk threads used for • trapping insects • Line their nests • Form sperm webs or egg sacs • Warning threads, molting threads, nursery webs • Wrap prey securely

26. Spider Web

27. Class ArachnidaOrder Araneae: Spiders • Are Spiders Really Dangerous • Timid creatures; more of an allies in the conflict with insects • Venom usually harmless to humans • Bite only when threatened or defending eggs or young • Two genera (in the United States) can give severe or fatal bites • Black widows (Latrodectusmactans) • Brown recluse (Loxoscelesreclusa)

28. Class ArachnidaOrder Araneae: Spiders • Black widow • Moderate to small in size • Shiny black, with a bright orange or red “hourglass” on the underside of their abdomen • Venom is neurotoxic • Acts on the nervous system • 4-5 of each 1000 bites are reported fatal

29. Class ArachnidaOrder Araneae: Spiders • Brown Recluse • Smaller than black widows • Brown, and bear a violin-shaped dorsal stripe on their cephalothorax • Venom is hemolytic • destroying tissues and skin surrounding a bite • Bite can be mild to serious and occasionally fatal

30. Brown Recluse Bite

31. Brown Recluse Bite

32. Brown Recluse Bite

33. Class ArachnidaOrder Scorpionida: Scorpions • Common in tropical & subtropical regions • Generally secretive • Feed on insects & spiders • Seize with clawlike pedipalps & rip with jawlike chelicerae • Short cephalothorax • Bears appendages • 1-6 pairs of eye • Abdomen • Preabdomen • Postabdomen • Tail-like structure ending in a stinging apparatus • Injects venom (most are not harmful to humans)

34. Great Hairy Scorpion – largest in US (up to 6”)

35. Scorpion’s glow under black light

36. Class ArachnidaOrder Opiliones: Harvestmen • “daddy longlegs” • Broad joining of the abdomen & cephalothorx • 4 pairs of long spindly legs • Can cast off legs if grasped by a predator • Chelicerae are pincherlike • Feed mostly as scavengers

37. Class ArachnidaOrder Acari: Ticks & Mites • Cephalothorax & Abdomen completely fused • Capitulum • Anterior projection that carries mouth parts • Found everywhere, over 25,000 species

38. Class ArachnidaOrder Acari: Ticks & Mites • Mites • sometimes cause allergies and dermatoses • Agricultural pests • Feed on dermal tissue of terrestrial vertebrates • Ticks • Larger than mites • Suck blood until enormously distended • are among the world’s premier disease vectors, • second only to mosquitoes • (Lyme disease, Rocky Mountain spotted fever, tularemia, Texas cattle fever, etc)