1. Ch 38 – Phylum Arthropoda

2. Characteristics of Arthropods Segmented (Arthropod means “jointed foot” Segmented (Arthropod means “jointed foot” Body segments have jointed appendages Body segments have jointed appendages Exoskeleton Exoskeleton Provides protection and support Provides protection and support Made of 3 layers excreted by the epidermis Made of 3 layers excreted by the epidermis Outer layer – waxy, mix of proteins and lipids Outer layer – waxy, mix of proteins and lipids –Repels water and prevents dessication Middle layer – primary protection, protein and chitin Middle layer – primary protection, protein and chitin Inner layer – flexible at joints, protein and chitin Inner layer – flexible at joints, protein and chitin –Muscles attach to move body segments

4. Characteristics Cont’d True Coelom True Coelom Bilateral symmetry Bilateral symmetry Cephalization Cephalization Variety of appendages around mouth Variety of appendages around mouth Most have segmented antennae at anterior Most have segmented antennae at anterior Compound eyes Compound eyes Made of many individual light detectors Made of many individual light detectors Sense light intensity Sense light intensity –Send impulses to brain, then move along ventral nerve cord Open circulatory system Open circulatory system

5. Molting B/c of exoskeleton, arthropods can’t grow without periodically shedding B/c of exoskeleton, arthropods can’t grow without periodically shedding In between molts: In between molts: Tissues swell to put pressure on exoskeleton Tissues swell to put pressure on exoskeleton Hormone is released Hormone is released Epidermis secretes enzymes to digest inner layer Epidermis secretes enzymes to digest inner layer Uses this material to build new exoskeleton Uses this material to build new exoskeleton Outer layer loosens and breaks Outer layer loosens and breaks

6. Molting Cont’d Takes days for new exoskeleton to become hard Takes days for new exoskeleton to become hard Very vulnerable during this time Very vulnerable during this time

7. Evolution and Classification ¾ of all animal species belong to this phylum ¾ of all animal species belong to this phylum Extremely diverse Extremely diverse Lobsters, crabs, spiders, centipedes, insects, etc. Lobsters, crabs, spiders, centipedes, insects, etc. First appeared more than 600 mya First appeared more than 600 mya Various groups have undergone evolutionary changes Various groups have undergone evolutionary changes Scientists still believe they had a common ancestor Scientists still believe they had a common ancestor Ancestor: body segments identical, Living species: Specialized tagmata Ancestor: body segments identical, Living species: Specialized tagmata

8. Evolution and Classification Cont’d Divided in 4 subphyla Divided in 4 subphyla Trilobita (extinct animals called trilobites) Trilobita (extinct animals called trilobites) Crustacea - Lobsters, crabs, crayfish, etc. Crustacea - Lobsters, crabs, crayfish, etc. Have pair of chewing mouthparts - mandibles Have pair of chewing mouthparts - mandibles Chelicerata – spiders, scorpions, ticks, etc. Chelicerata – spiders, scorpions, ticks, etc. No antennae, pincerlike mouthparts - chelicerae No antennae, pincerlike mouthparts - chelicerae Uniramia – centipedes, millipedes, insects Uniramia – centipedes, millipedes, insects Have antennae and mandibles, appendages are unbranched Have antennae and mandibles, appendages are unbranched

10. 38-2 Subphylum Crustacea

11. Characteristics 2 pairs of appendages on head – feelers 2 pairs of appendages on head – feelers Each other body segment generally has a pair of appendages Each other body segment generally has a pair of appendages Some are branched Some are branched

12. Characteristics Cont’d Exoskeletons contain large amounts of CaCO 3 Exoskeletons contain large amounts of CaCO 3 Gas exchange Gas exchange Some through exoskeleton, some gills Some through exoskeleton, some gills Development Development Most have free-swimming larva called a nauplius Most have free-swimming larva called a nauplius 3 pair appendages, 1 eye 3 pair appendages, 1 eye Takes adult form through series of molts Takes adult form through series of molts

13. Characteristics - Size Large range, but mostly small Large range, but mostly small Small Small Copepods and Water fleas Copepods and Water fleas Size of a comma Size of a comma Copepods = ocean plankton Copepods = ocean plankton Large Large Japanese Spider Crab Japanese Spider Crab 14 foot leg span 14 foot leg span

14. The Crayfish Freshwater relative of lobster Freshwater relative of lobster Decapod = 5 pairs of legs Decapod = 5 pairs of legs

15. External Structure Body divided into 2 main parts Body divided into 2 main parts Cephalothorax Cephalothorax Consists of 2 tagmata Consists of 2 tagmata Head – 5 segments Head – 5 segments Thorax – 8 segments, posterior to head Thorax – 8 segments, posterior to head Dorsal exoskeleton fused into the Dorsal exoskeleton fused into the carapace Abdomen Abdomen Lies posterior to cephalothorax, 7 segments Lies posterior to cephalothorax, 7 segments 7 th is called the telson, forms flat paddle 7 th is called the telson, forms flat paddle

16. External Structure Cont’d Pair of app. attached to each segment (except telson) See chart pg. 749 Pair of app. attached to each segment (except telson) See chart pg. 749 Antennules and Antennae: feelers sensitive to touch, taste Antennules and Antennae: feelers sensitive to touch, taste Mandible: Chews food Mandible: Chews food Maxilla: 2 pairs, manipulate food, assist with respiration Maxilla: 2 pairs, manipulate food, assist with respiration Maxillipeds: 3 pairs, manipulate food, sensitive to touch and taste Maxillipeds: 3 pairs, manipulate food, sensitive to touch and taste

17. External Structure Cont’d Chelipeds: Most anterior on thorax, end in large pincers Chelipeds: Most anterior on thorax, end in large pincers For capturing food and defense For capturing food and defense Walking leg: 4 pairs, movement over solid surface Walking leg: 4 pairs, movement over solid surface First two pairs end in small pincers for grasping First two pairs end in small pincers for grasping Swimmeret: attached to five abdominal segments Swimmeret: attached to five abdominal segments Create water currents and used in reproduction Create water currents and used in reproduction Uropod: On sixth abdominal segment, used for propulsion Uropod: On sixth abdominal segment, used for propulsion

18. Crayfish Ventral View

19. Crayfish - Digestion Food passes through esophagus to stomach Food passes through esophagus to stomach Stomach grinds food into fine paste Stomach grinds food into fine paste Uses teeth made of chitin and CaCO3 Uses teeth made of chitin and CaCO3 Paste mixed with enzymes excreted by a digestive gland Paste mixed with enzymes excreted by a digestive gland Moves through intestine (further digestion and absorption) Moves through intestine (further digestion and absorption) Waste leaves body via anus Waste leaves body via anus

20. Crayfish – Respiration Use gills Use gills Extend from base of each walking leg into chamber under carapace Extend from base of each walking leg into chamber under carapace Legs circulate water across gills during walking Legs circulate water across gills during walking Posterior pair of maxillae as well Posterior pair of maxillae as well Each gill covered by extension of exoskeleton Each gill covered by extension of exoskeleton Thin enough for gas exchange Thin enough for gas exchange

21. Crayfish - Circulation Excess water eliminated through organs called green glands Excess water eliminated through organs called green glands Open circulatory system Open circulatory system Dorsal heart Dorsal heart Pumps hemolymph through vessels Pumps hemolymph through vessels Hemolymph enters hemocoel, bathing tissues Hemolymph enters hemocoel, bathing tissues Passes through gills for gas exchange Passes through gills for gas exchange Returns to heart Returns to heart

22. Crayfish – Nervous system Brain (pair of ganglia) located above esophagus Brain (pair of ganglia) located above esophagus Receives impulses from eyes, antennae, antennules Receives impulses from eyes, antennae, antennules Nerves extend down to control mouth appendages Nerves extend down to control mouth appendages Ventral nerve cord runs posteriorly Ventral nerve cord runs posteriorly

23. 38-3 Subphylum - Chelicerata Class Arachnida Class Arachnida

24. Class: Arachnida Includes spiders, scorpions, mites, & ticks Includes spiders, scorpions, mites, & ticks Body is divided into cephalothorax and abdomen (similar to crayfish) Body is divided into cephalothorax and abdomen (similar to crayfish) Cephalothorax usually includes: Cephalothorax usually includes: 6 pairs jointed appendages 6 pairs jointed appendages 1 pair chelicerae (picher-like mouthparts) 1 pair chelicerae (picher-like mouthparts) 1 pair pedipalps 1 pair pedipalps Aid in holding food and chewing Aid in holding food and chewing 4 pairs of walking legs 4 pairs of walking legs

26. Spider Anatomy Body is pinched b/t cephalothorax and abdomen Body is pinched b/t cephalothorax and abdomen Chelicerae modified as fangs used to inject venom Chelicerae modified as fangs used to inject venom Venom produced by poison glands in the CT Venom produced by poison glands in the CT Flows through ducts in chelicerae to tips Flows through ducts in chelicerae to tips Most have 8 simple eyes Most have 8 simple eyes

27. Spider Anatomy cont’d Posterior tip of abdomen has 3 pairs of organs called spinnerets Posterior tip of abdomen has 3 pairs of organs called spinnerets Each made of hundreds of microscopic tubes Each made of hundreds of microscopic tubes Connect to silk glands in abdomen Connect to silk glands in abdomen Fluid made from protein hardens into threads as it is pulled from the spinnerets Fluid made from protein hardens into threads as it is pulled from the spinnerets Used to spin webs, build nests, protect eggs Used to spin webs, build nests, protect eggs Some move to a new habitat by allowing wind to pull their threads Some move to a new habitat by allowing wind to pull their threads

29. Spider Anatomy Cont’d Nervous, digestive, circulatory systems all very similar to crustaceans Nervous, digestive, circulatory systems all very similar to crustaceans Respiratory system is different (terrestrial!) Respiratory system is different (terrestrial!) Book lungs: paired sacs in the abdomen with many folds for gas exhange Book lungs: paired sacs in the abdomen with many folds for gas exhangeAnd/or Tracheae: system of tubes that carry air directly to tissues Tracheae: system of tubes that carry air directly to tissues Through openings in exoskeleton called spiracles Through openings in exoskeleton called spiracles

30. Spider Anatomy Cont’d Excretory system – modified for land Excretory system – modified for land Malpighian tubules: hollow projections of digestive tract Malpighian tubules: hollow projections of digestive tract Collect body fluids and waste, carry to intestine Collect body fluids and waste, carry to intestine Most water reabsorbed, wastes leave body in solid form Most water reabsorbed, wastes leave body in solid form Coxal glands Coxal glands Organs that remove wastes and discharge them through openings at the base of some legs Organs that remove wastes and discharge them through openings at the base of some legs

31. Life of a Spider Feed mostly on insects, some can catch fish frogs, or birds Feed mostly on insects, some can catch fish frogs, or birds Many predator adaptations Many predator adaptations Chase, Trapdoor, Snare Chase, Trapdoor, Snare Male usually smaller than female Male usually smaller than female As soon a sperm is transferred to female, the male moves away quickly As soon a sperm is transferred to female, the male moves away quickly May get eaten if he isn’t fast enough May get eaten if he isn’t fast enough Female then puts fertilized eggs in silken case Female then puts fertilized eggs in silken case Carries it or attaches it to something Carries it or attaches it to something

32. Life of a Spider Cont’d Most venom harmless to humans Most venom harmless to humans only 2 fatal species in U.S. only 2 fatal species in U.S. Black Widow Black Widow Red/orange hourglass shaped mark ventral abdomen Red/orange hourglass shaped mark ventral abdomen Venom attacks nervous system Venom attacks nervous system Brown Recluse Brown Recluse Violin shaped mark on dorsal cephalothorax Violin shaped mark on dorsal cephalothorax Venom digests tissues surrounding the bite Venom digests tissues surrounding the bite

34. Scorpions Differ from spiders in 2 ways Differ from spiders in 2 ways Large pincerlike pedipalps Large pincerlike pedipalps Large stinger on the last abdomen segment Large stinger on the last abdomen segment Curled over body Curled over body Usually nocturnal hunters Usually nocturnal hunters Prefer tropical or desert climates Prefer tropical or desert climates

35. chelicerae eyespedipalp

36. Mites and Ticks Completely fused CT and abdomen Completely fused CT and abdomen Mites Mites Most less than 1 mm in length Most less than 1 mm in length Both free living and parasitic Both free living and parasitic Ticks Ticks Range from a few mm to over an inch Range from a few mm to over an inch Many parasitic Many parasitic Can transmit Rocky Mountain Spotted Fever and Lyme disease Can transmit Rocky Mountain Spotted Fever and Lyme disease

37. pedipalps & chelicerae cephalothorax abdomen Mite and Tick Body Regions

38. American dog tick male Blacklegged (deer) tick female

39. American dog tick female laying egg mass (1000-2000 eggs!).

40. Subphylum – Uniramia Myriapods Myriapods Could have been first animals to appear on land Could have been first animals to appear on land Highly segmented Highly segmented Little variation to appendages Little variation to appendages No waxy exoskeleton No waxy exoskeleton Live in damp environment Live in damp environment

41. Class – Diplopoda Millipedes Millipedes 2 pairs of legs per segment 2 pairs of legs per segment Adapted for burrowing through soil Adapted for burrowing through soil Move slowly (legs are short) Move slowly (legs are short) Rounded bodies Rounded bodies Eat plant matter Eat plant matter Short antennae, 2 groups simple eyes Short antennae, 2 groups simple eyes Bad vision, good sense of smell Bad vision, good sense of smell

42. Class – Chilopoda Centipedes Centipedes 15-175 pairs of legs 15-175 pairs of legs 1 pair per segment 1 pair per segment Can be very large in tropical regions Can be very large in tropical regions Flattened bodies Flattened bodies 1st segment app. modified as poison claws 1st segment app. modified as poison claws Predatory Predatory Move quickly in search of prey (earthworms, insects, etc.) Move quickly in search of prey (earthworms, insects, etc.)