Arthropods

1. Arthropods Diverse phylum containing three-fourths of all animal species that live in almost every environment on Earth. Includes lobsters, crabs, spiders, millipedes, centipedes and insects!

3. Arthropods Their name means �jointed foot� Segmented bodies with 6 or more jointed appendages

4. Exoskeleton made of proteins, chitin, lipids and some have calcium carbonate Inner layer flexible for movement Middle layer for protection Arthropods

5. Body Systems Highly Cephalized True coelom Open circulatory system

6. Body Systems Most have segmented antennae Sensing environment and chemicals Eyes Compound many � many light detectors Simple eyes - several Sensing environment and chemicals

7. Body Systems Smooth and striated muscles that attach to inner layer of exoskeleton Dioecious (separate sexes) Internal fertilization Most lay eggs that develop into the same form as an adult or undergo metamorphosis

8. Nervous System & Symmetry Similar to annelida Nerve cord linked to ganglia throughout body Nerve ring surrounds pharynx

9. Molting (Ecdysis) Exoskeleton must be shed to grow Hormone digests inner skeletal layer at the same time it synthesizes new exoskeleton using digested material Old skeleton splits down back of thorax Time needed for new exoskeleton to harden making animal vulnerable to predators or desiccation (terrestrial)

10. Molting

12. Crawfish Characteristic and Anatomy

13. External Anatomy Crawfish are a decapod - it has ten feet Two major sections to a crawfish body Chephalothorax = fused head and thorax Carapace � tough covering (shell) over the cephalothorax

14. External Anatomy Abdomen � posterior segment that holds digestive & reproductive organs Telson � center flat paddle at the posterior end of crayfish Uropods � sides of telson; help propel crayfish during tailflips

15. Appendages Each segment has a pair appendages attached to it Antennules � feelers sensitive to touch, taste and equilibrium Antennea � feelers that respond to touch and taste Maxillae - manipulate food Mandibles - chew food Chelipeds - most anterior appendages have large pinchers for capturing food and for defense Walking leg � locomotion over solid surfaces Swimmeret � Anterior abdomen - create water currents, transfer sperm (males) and carry eggs and young (females)

17. Digestion & Excretion Food passes through esophagus to stomach that has teeth made of chitin and calcium carbonate to grind food into a paste Digestive gland excretes enzymes that mix with paste then food enters intestine for further digestion and absorption. Undigested material leaves through anus

18. Respiration Gills for respiration � feathery branches (2) on posterior pair of maxillae directs water over gills

23. Circulatory System Open circulatory system Dorsal heart pumps hemolymph into large vessels Hemolymph leaves vessels enters hemocoel bathing tissues in O2 rich hemolymph passes gills exchange O2 for CO2, returns to dorsal vessels & enters heart

24. Circulatory System Green gland � eliminates excess solutes from hemolymph Crayfish live in hypotonic environment � solute molecules higher in surroundings than in crayfish cells

25. Neural Control Brain consists of pair of ganglia above the esophagus receives impulses from eyes, antennules and antennae 2 nerve fiber bundles extend from brain to a ganglion that controls mandibles, maxillae and maxillepeds. Ventral nerve cord runs posterior to this ganglion and connects muscles in the thorax and abdomen Sense vibrations & chemicals with small sensory hairs projecting from exoskeleton

28. Chelicerata & Uniramia 

29. Chelicerata & Uniramia Most are terresterial Chelicerata Arachnida � 70,000 species � spiders, scorpions, mites and ticks Uniramia Myriapods � many feet Diplopoda - millipedes Chilopoda - centipedes

30. Arachnida Spiders, scorpions, mites and ticks Body divided into cephalothorax and abdomen Cephalothroax usually has 6 pair of jointed appendages One pair of chilicerae One pair of pedipalps � aid in holding food and chewing Four pairs of walking legs

33. Arachnid Anatomy Length ranges from 0.5 mm to 9 cm (3.5 inches) Chelicerae modified as fangs to inject venom Venom produced by poison gland Most have 8 simple eyes each with a single lens

38. 3 pair of spinnerets � silk producing structures that are made of spigots (microscopic tubes) Protein containing fluid produced in silk glands hardens into threads as it is pulled from the spinnerets

39. Garden Spider � web is easily identified by the zigzag woven in

41. Respiratory System Terrestrial animals have different respiratory systems vs. aquatic crustaceans Some spiders have book lungs �paired sacs in the abdomen with parallel folds that look like pages of a book Some spiders have tracheae � air tubes that carry air directly to the tissues from the spiracles - openings in the exoskeleton Some spiders have both book lungs & tracheae

43. Circulation Spider's blood is hemolymph that circulates oxygen, nutrients & hormones to the different organs in the body using an open circulatory system Simple heart - a tube surrounded by a muscle, with a one-way valve on each end - pumps blood into the body cavity, all around the spider's organs. Organs get oxygen because they're soaking in (hemolymph) blood.

45. Nervous System One of the most amazing things about spiders is how much they can accomplish with a small brain. The spider's central nervous system is made up of two simple ganglia, or nerve cell clusters, connected to nerves leading to the spider's various muscles and sensory systems

47. Excretory System Modified for terrestrial life Malpighian tubules � hollow projections of digestive tract that collect body fluids and wastes and carry them to intestine Coxal glands remove wastes & discharge waste through openings at base of the legs

48. Spider Facts Feed mainly on insects Most venom harmless to humans Exceptions: Black widow � venom attacks nervous system Brown recluse � venom digests tissue surround bite site

49. Spider Facts Male spiders smaller than females usually Reproduction occurs when male transfers sperm to sacs in the pedipalps and moved to the seminal receptacle of the female Male has to be quick at the transfer or the female may eat him Females attach eggs to web or carry them with. Young spiders hatch in about 2 weeks

51. Scapulae pads allow spiders to climb surfaces such as glass

52. Scorpions Have large pincher like pedipalps Large stinger on last abdomen segment Hunt at night; hide during day Capture prey with pedipalps then inject venom into prey with their stinger Venom of a few species fatal to humans Tropical or semitropical or desert areas

53. The scorpion has two parts, a cephalothorax & abdomen Cephalothorax is covered by a carapace Pair of median eyes & 2 to 5 pairs of lateral at the front corners of the chitinous carapace Chelicerae & a pair of pedipalps, used for prey capture and mating complete the head anatomy Pedipalps are covered with trichobothria, sensory setae, that sense air-borne vibrations

54. The abdomen =main body & the tail Main body is covered by bony armor protects the lungs, digestive organs & reproductive organs & has 4 pairs of walking legs attached Tips of legs have pectines, small organs that detect ground vibrations. These feathery sensory organs lie beneath the abdomen & trail on the ground & are covered by chemosensors

55. Tail curves up & ends in the telson with the bulbous vesicle containing the venom glands & a sharp, curved aculeus that delivers the venom Deadly Scorpions http://web.singnet.com.sg/~chuaeecc/venom/venom2.htm

56. Most species of scorpions grow to 2 - 3 in The longest scorpion in the world is the African Scorpion (Hadogenes troglodytes) -over 8 in. long In U.S., members of the genus Hadrurus � giant desert hairy scorpions are the largest - about 5 in long

57. Mites and Ticks Most abundant (30,000 species) & most specialized arachnid Have completely fused cephalothorax and abdomen (one tagmata)

58. Mites Most mites less than 1 mm Mites are parasites or free living (parasitic at one point in life cycle) Break skin w/ chelicerae & feed on blood Causes swelling and itching

59. Ticks Length 2 mm to 3 cm Parasitic ticks pierce hosts skin Feed on blood and can transmit bacteria & microorganisms Lyme disease Rocky Mountain spotted fever Patient in waiting for host to approach http://www.idph.state.il.us/envhealth/pdf/Tickpstr.pdf

60. Bad Bugs Slide Show http://www.emedicinehealth.com/slideshow_bad_bugs/article_em.htm

61. Myriapods Millipedes (Diplopoda) and centipedes (Chilopoda) both in subphylum Unaramia May have been first animal to appear on land Bodies have numerous segments with little variety in appendages Single pair of unbranched antennae No waxy exoskeleton Avoid desiccation by living in damp environments (under leaves, rocks & logs)

62. Diploda Millipedes have 2 pair of legs on each body segment (except last 2 segments) Legs adapted for burrowing Move slowly (short legs) Short antennae 2 groups of simple eyes w/ poor vision Good sense of smell Consume plants and detritus Coil when threatened & some secrete noxoius fluid containing cyanide

63. Chilopoda From 15 to 175 pairs of legs w/ one pair per body segment (except 1st & last) Body flatter than millipede Can grow to 30 cm (12 in) Have modified pair of poison claws on first segment Long antennae 2 clusters of simple eyes Consume earthworms, insects and other prey Most not harmful to humans