Classification- Phylum Arthropoda Chapter 19 Subphylum Trilobita (extinct) Subphylum Chelicerata

1. Classification- Phylum Arthropoda Chapter 19 • Subphylum Trilobita (extinct) • Subphylum Chelicerata • Class Arachnida • Order Araneae • Order Scorpiones • Order Opiliones (Daddy Longlegs) • Order Acari (Ticks and Mites) • Subphylum Myriapoda • Class Diplopoda • Class Chilopoda Chapter 20 • Subphylum Crustacea Chapter 21 • Subphylum Hexapoda

2. CHAPTER 19 Trilobites, Chelicerates, and Myriapods 19-2

4. Characteristics Anthropodization • Soft cuticle of the arthropod ancestors was stiffened by deposition of protein and chitin • Joints had to provide flexibility • Sequence of molts was necessary to allow for growth • Molting required hormonal control • Hydrostatic skeleton function was lost • Coelom regressed and was replaced by open sinuses • Motile cilia were lost

5. Characteristics Phylum Arthropoda • Contains over 3/4 of all known species • Coelomate protostomes with well-developed organ systems • Segmented

6. Characteristics • Sizes range from the Japanese crab (four meters in leg span) to the 0.1 mm long follicle mite • Abundance and wide ecological distribution makes them the most diverse animal group • Some are agents of disease and compete with humans for food • Others are beneficial • All modes of feeding occur among arthropods; carnivores, omnivores, herbivorous (most), decomposers, scavengers, parasites, etc.

7. Japanese Spider Crap Follicle Mite

8. Characteristics Relationships among arthropod subgroups • Divided into subphyla based on relationships between subgroups • Groupings among subphyla based on molecular data • Centipedes, millipedes are placed into subphylum Myriapoda • Insects are placed in subphylum Hexapoda • Spiders, and ticks form subphylum Chelicerata • Lobsters, crabs, barnacles, and others form subphylum Crustacea

9. 2 Important Parts in Arthropods: Appendages and Mouthparts Uniramous: single branched Biramous: 2 branches Chelicerae: pointed appendages to grasp food Mandible: chewing appendage

11. Great Diversity and Abundance of Arthropods WHY HAVE ARTHROPODS SURVIVED… • 1. Versatile Exoskeleton • Cuticle is highly protective and jointed, providing mobility • Consists of inner thick procuticle and outer thin epicuticle • Procuticle has an exocuticle secreted before a molt and an endocuticle secreted after molting • Both layers of procuticle contain chitin bound with protein • Procuticle is lightweight, flexible, and protects against dehydration

13. Great Diversity and Abundance of Arthropods • Cuticle is further hardened by tanning • Ecdysis, or molting • Process of shedding outer covering and growing a new, larger one • Arthropods typically molt four to seven times

14. Survival of Arthropods • 2. Segmentation and Appendages for Efficient Locomotion • Appendages often highly specialized for division of labor • Limb segments are hollow levers with internal striated muscles • Appendages may function in sensing, food handling, walking, or swimming • 3. Use of Diverse Resources through Metamorphosis • Many arthropods undergo metamorphic changes leading to different larval and adult stages • Larvae and adults feed on different organisms and occupy different habitats • Avoid competition

15. Survival of Arthropods • 4. Air Piped Directly to Cells • Terrestrial arthropods • Use an efficient tracheal system for oxygen transport directly to tissues • Aquatic arthropods • Respire via various forms of gills • 5. Highly Developed Sensory Organs • Eyes vary from simple light sensitive ocelli to a compound mosaic eye • Other sensory structures for touch, smell, hearing, balancing, and chemical reception

16. Early Arthropod fossils: Trilobites and Eurypterid

17. Subphylum Chelicerata Characteristics • Chelicerates have six pairs of cephalothoracic appendages including chelicerae (eating), pedipalps (mating) and four pair of legs • Lack mandibles and antennae • Most suck liquid food from prey • Example: spiders, horseshoe crabs, sea spiders, ticks, scorpions

18. Spiders Sea Spiders Horseshoe Crabs

19. Horseshoe Crab: Illustrating 6 pairs of appendages

20. Sea spiders: Illustrating 6 sets of appendages

21. Subphylum Chelicerata Class Arachnida • Great diversity • Most are free living and more common in warm, dry regions Structures • Divided into two body parts: a cephalothorax and an abdomen • Cephalothorax bears a pair of chelicerae, a pair of pedipalps, and 4 pairs of walking legs • No antenna and mandibles • Example: Spiders, Ticks, and Scorpions

22. Subphylum Chelicerata • Most are predaceous and have claws, fangs, poison glands, or stingers • Sucking mouthparts ingest fluids and soft tissues from bodies of their prey • Spiders have spinning glands • Pedipalps of males are modified, sometimes elaborately, for sperm transfer

23. Subphylum Chelicerata • Over 80,000 species have been described • Most harmless to humans and provide essential control of injurious insects • Some spiders are venomous and can cause pain or death in humans • Ticks may carry human diseases • Mites can be crop pests

24. Subphylum Chelicerata Order Araneae: Spiders • Approximately 40,000 species • Body consists of an unsegmented cephalothorax and abdomen joined by a slender pedicel • Anterior appendages are a pair of chelicerae with terminal fangs • Pair of pedipalps have sensory functions and are used by males to transfer sperm • Basal parts of pedipalps used to handle food • Four pairs of walking legs terminate in claws • All are predaceous, mostly on insects

25. External Anatomy of Jumping Spider

26. Subphylum Chelicerata • Injected venom liquefies and digests the tissues which is sucked into spider’s stomach • RESPIRATORY SYSTEM • Breathe by book lungs and/or trachea • Book lungs unique to spiders • Parallel air pockets extend into blood-filled chamber • Air enters chamber through a slit in body wall • Trachea system • Transports air directly to tissues/blood through an opening called a spiracle • Excretory System • In spiders and insects, Malpighian tubules serve as excretory structures • Rectal glands reabsorb water. Conserves water and allows the organisms to live in dry environments

27. Internal Anatomy of a Spider

28. Subphylum Chelicerata • Sensory Systems • Most spiders have eight simple eyes, each with a lens, optic rods, and a retina • Detect movement and may form images • Sensory setae detect air currents, web vibrations, and other stimuli • Vision is poor, rely on mechanoreceptors (stimuli)

29. Subphylum Chelicerata • Web-Spinning Habits • Spinning silk critical ability for spiders • Two or three pairs of spinnerets contain microscopic tubes that run to silk glands • Liquid scleroprotein secretion hardens as it is extruded from spinnerets • Silk threads are very strong and will stretch considerably before breaking • Silk is used for orb webs, lining burrows, forming egg sacs, and wrapping prey

30. Grasshopper snared in Golden Garden Spider silk. If the spider is not hungry, it will save the live prey for later.

31. Fisher Spider: Catches prey, paralyzes them, pumps in digestive enzymes, then sucks out predigested contents.

32. Subphylum Chelicerata • Reproduction • Before mating, male stores sperm in pedipalps • Mating involves inserting pedipalps into the female genital openings • A courtship ritual is often required before the female will allow mating • Eggs may develop in a cocoon in the web or may be carried by female • Young hatch in about two weeks and may molt before leaving the egg cocoon

33. Wolf spider with egg sack Black Widow with egg sack

34. Subphylum Chelicerata • Are spiders really dangerous? • Most people fear spiders without good reason • Spiders are allies of humans in our battle with insects • American tarantulas rarely bite, and bite is not dangerous • Species of black widow spiders are dangerous • Venom is neurotoxic • Brown recluse spider • Hemolytic venom that destroys tissue around the bite • Some Australian and South American spiders are the most dangerous and aggressive

35. Tarantula: Not Dangerous. Bite similar to Bee Sting Bite when threatened or defending eggs/young.

36. A: Black Widow displaying Red Hourglass B: Brown Recluse Spider displaying violin marking on cephalothorax

37. Subphylum Chelicerata Order Scorpionida: Scorpions • More common in tropical and subtropical zones but occur in temperate areas • Approximately 1,400 species worldwide • Nocturnal and feed largely on insects and spiders • Sand-dwellers locate prey by detecting surface waves with leg sensillae • Appendages attached to cephalothorax • Pair of medial eyes and 2–5 lateral eyes • Preabdomen has 7 segments • Postabdomen has long, slender tail of five segments that ends in a stinging apparatus

38. Emperor Scorpion with young. Young stay with mother until their first molt. Harvestmen: Order Opiliones AKA- Daddy Longlegs

39. Subphylum Chelicerata • Under the abdomen are comblike pectines • Explore the ground and aid in sex recognition • Stinger on last segment has venom that varies from mildly painful to dangerous • Ovoviviparous or viviparous and produce from 6 to 90 young • Perform complex mating dances • In some species the male stings the female on pedipalp or on edge of cephalothorax

40. Subphylum Chelicerata Order Opiliones: Harvestmen • Harvestmen or daddy longlegs • Approximately 5,000 species worldwide • Unlike spiders, abdomen and cephalothorax join broadly without a narrow pedicel • Can lose most of their eight long legs without ill effect • Chelicerae are pincerlike • Mostly scavengers • Have 2 eyes, not 8

41. Subphylum Chelicerata Order Acari: Ticks and Mites • Medically and economically the most important arachnids • About 30,000 species have been described • Both aquatic and terrestrial • Inhabit deserts, polar areas, and hot springs • Most mites are less than 1 millimeter long • Ticks may range up to 2 cm • Complete fusion of cephalothorax and abdomen • No sign of external segmentation

42. Subphylum Chelicerata • Mouthparts on tip of the anterior capitulum • Chelicerae on each side help pierce, tear, or grip food • Adult mites and ticks possess 4 pairs of legs • Transfer sperm directly or by spermatophores (packets of sperm) • Egg hatches, releasing a six-legged larva • Eight-legged nymph stages follow

43. Wood Tick All stages are ectoparasites Red Velvet Mite: Trombicula Only Larvae is ectoparasite

44. Subphylum Chelicerata • House dust mites • Free-living and often cause allergies • Spider mites • One of many important agricultural pest mites that suck out plant nutrients • Chiggers • Larval Trombicula mites • Feed on dermal tissues and cause skin irritation • Hair follicle mite Demodex • Harmless but may cause mild dermatitis

45. Human Follicle Mite

46. Subphylum Chelicerata • Human itch mite • Causes intense itching • Popular in WWII - due to crowded conditions in which people lived Human Itch Mite

47. Subphylum Chelicerata • Ticks: 2nd premier disease vector (after mosquito). • Species include: • Ixodes • Some carry Lyme disease • Bacterial infection dicovered in 1970, in the city of Lyme, Conneticut. • Dermacentor • Transmit Rocky Mountain spotted fever • Cattle tick • Transmits Texas cattle fever (Protozoan)

48. Tick: Carries Texas Cattle Fever

49. Subphylum Myriapoda Characteristics • Myriopods (“Many Footed”) include: • Chilopoda (centipedes) • Diplopoda (millipedes) • Use trachea to transport respiratory gases to all body tissue • Excretion usually by Malpighian tubules