1. Arthropods

2. Why have they achieved so much diversity and abundance?
Versatile exoskeleton
Segmentation and appendages for more efficient locomotion
Air piped directly to cells
Highly developed sensory organs
Complex behavior patterns
Reduced competition through metamorphosis

3. Versatile exoskeleton
Highly protective, yet highly mobile
Exoskeleton: several layers of cuticle
covering secreted by underlying epidermis
Procuticle
Inner, thicker cuticle
Composed of chitin bound with protein
Tough, resistant, nitrogenous polysaccharide that is insoluble in water, alkalies, and weak acids
Crustaceans procuticle impregnated with calcium salts (<flexibility, >hardness)
Divided into two parts:
Exocuticle (secreted before a molt)
Endocuticle (secreted after molting)
Epicuticle
Thin
Composed of protein and lipids

4. Ecdysis (molting)

5. Segmentation and appendages for more efficient locomotion
Each segment has a pair of jointed appendages
can be modified:
Segments and appendages can be specialized for adaptive functions
Limb segments- hollow levers moved by striated muscles (good for rapid actions)
Jointed appendages- equipped with sensory hairs
Modified for sensory functions, food handling, and swift/efficient walking or swimming

6. Air piped directly to cells
Land arthropods
Highly efficient tracheal system of air tubes
Tubes deliver oxygen directly to tissues and cells for high metabolic rate
Aquatic arthropods
Breath mainly from some form of gill

7. Highly developed sensory organs
Arthropods are very alert to environmental stimuli
Compound (mosaic) eyes
Other senses of:
Touch (what organ system?)
Smell (what organ system?)
Hearing (what organ system?)
Balance (what organ system?)
Chemical reception (what organ system?)

8. Complex behavior patterns
Innate behavior
Unlearned behavior controls much of what arthropods do
Learned behavior
Habituation (ignore repeated harmless stimuli)
Imprinting (colony scents)
Classical conditioning (food scents)
Waggle dance (bees)

9. Reduced competition through metamorphosis
Larval forms
Quite different from adults = less competition within species
Larval forms adapted for fulfilling a different niche than adults
Different foods
Different habitats

10. Let’s explore the different subphyla
Subphylum Trilobita
Subphylum Chelicerata
Subphylum Crustacea
Subphylum Myriapoda
Subphylum Hexapoda

11. Subphylum Trilobita Extinct for over 200 million years
Abundant during the Cambrian & Ordovican periods
Named for tri-lobed shape of body caused by a pair of longitudinal grooves
Bottom dwellers, probably scavengers
Could roll up like rollie-pollies

12. Subphylum Chelicerata
Horseshoe crabs, spiders, ticks, mites, scorpions, sea spiders, etc
Characterized by:
Two tagmata
Six pairs of appendages
Pair of chelicerae
Pair of pedipalps
Four pairs of walking legs (exception: horseshoe crabs)
No mandibles
No antennae
Most suck liquid food from their prey

13. Subphylum Chelicerata
Subclass Xiphosurida
Class Pycnogonida
Class Arachnida
Order Araneae
Order Scorpionida
Order Opiliones
Oder Acari

14. Subclass Xiphosurida: Horseshoe crabs
Dates from Cambrian period
Practically unchanged back to Triassic Period
Lives in shallow water along North American Atlantic coast
Swims (awkwardly) with abdominal plates; walks with walking legs
Feed at night – worms & small mollusks

15. Subclass Xiphosurida: Horseshoe crabs
Physical Features:
Carapace: Unsegmented, horseshoe-shaped, and hard dorsal shield
Broad abdomen
Telson: long spine-like tailpiece
Book gills: flat leaf-like gills
Exposed on some abdominal appendages
One pair chelicerae and 5 pairs of walking legs

16. CLass Pycnogonida: Sea Spiders
Physical Features:
4 pairs of thin, walking legs
Pair of ovigers (ovigerous legs)
Males carry egg masses on these legs
Reduced abdomen
Elongated cephalothorax
Large suctorial proboscis: suck juices from hydroids and soft-bodied animals
Ocean-dwellers
Few mm in length

17. Class Arachnida uber diverse: > 50,000 species described
Includes: spiders, scorpions, pesudoscorpions, whip scorpions, ticks, mites, harvestmen (daddy longlegs), etc…
Arachnid tagmata: cephalothorax & abdomen

18. Order Araneae: Spiders
>35,000 species worldwide
Predacious
Feed mainly on insects
Chase prey, ambush prey, or trap them in silk net
Feeding:
Chelicerae function as fangs with ducts from venom glands
Digestive enzymes liquefy tissue so broth can be sucked up
Some have teeth at base of chelicerae to crush or chew in addition to use of enzymes
Physical Features
Tagmata joined by pedicel
Narrow, waist-like structure connecting cephalothorax & abdomen

19. Spider Webs
2 or 3 spinnerets contain hundreds of microscopic tubules connect to abdominal silk glands
Silk thread created when liquid protein secretions hardens on contact with air
Fun facts:
silk threads stronger than steel threads of same diameter
2nd in torsional strength (fused quartz fiber is 1st)
Threads will stretch 1/5 of their length before breaking
webs used for:
Trap insects, line nests, form sperm webs or egg sacs, build draglines, make bride lines, warning threads, molting threads, attachment discs, nursery webs, or to securely wrap prey

20. Spider Webs
Orb Webs
Orb Webs
Drag Lines
Egg Cases

21. Dangerous?!? Most spiders are harmless to humans
Australia has some of the deadliest spiders (they have some of the deadliest organisms actually)
Atrax robustis
South America has a few dangerous spiders too
Phoneutria fera

22. Dangerous?!? In the U.S. Black widows Brown recluse
Latrodectus mactans
Venom is neurotoxic (acts on the nervous system)
Shiny black, red hourglass on ventral side of abdomen
Brown recluse
Loxosceles reclusa
Venom is hemolytic (destroys tissues and skin surrounding bite)
Brown, violin-shaped dorsal stripe on cephalothorax

23. Body Systems

24. Respiratory System Book lungs or tracheae (or both)
Book lungs- many parallel air pockets extending into a blood-filled chamber
Air enters chamber by a slit in body wall
Tracheae- system of air tubes that carry air directly to tissues from opening called spiracles

25. Excretory System Malpighian tubules Coxal glands
K, other solutes & wastes secrete into tubules
Tubules drain urine-like fluid into intestines
Rectal gland reabsorb K & H20
Wastes like uric acid
Nearly dry mixture of urine & feces left
Great adaptation (especially for arid conditions)- conserve fluids
Coxal glands
Modified nephridia base (coxa) of first & third walking legs

26. Nervous system 8 simple eyes Sensory setae Lens, optic rods, retina
Perception of moving objects
May form images for hunting/jumping spiders
Generally poor vision
Sensory setae
Hair-like structures that sense surroundings
i.e. air currents, changing tensions in the spider’s web
Web vibrations allow spider to sense size/activity of its prey, mate, or predator

27. Reproductive system Courtship rituals before mating Indirect mating
Male deposits sperm on a web he has spun prior to mating
Sperm package picked up/stored in cavities of pedipalps
Pedipalps = second pair of appendages that males use to transfer sperm into a female’s genital opening
Females can store sperm packets in seminal receptacle until eggs are ready (weeks or months)
Females lay fertilized eggs in silken cocoon
Carries around or attaches to web or plant
Cocoon may contain hundreds of eggs
Eggs hatch and young remain in egg sac for a few weeks feeding and growing for several molts

28. Reproductive System

29. Order Scorpionida: Scorpions
Range: tropical, subtropical, some temperate zones
Secretive: hiding in burrows or under objects by day; night
Predacious: insects & spiders
Reproduction
Bear live young
Mother carries on her back until after their first molt
Venom can be fatal in a few species from Africa, Mexico, Arizona, New Mexico, Australia, etc…
Androctonus
Centruroides

31. Physical features Claw-like pedipalps Jaw-like chelicerae
Short cephalothorax
1 – 6 pairs of eyes
appendages
segmented abdomen
Preabdomen- broad
Postabdomen- tail-like; ends in a stinging apparatus that injects venom

32. Order Opiliones: Harvestment “Daddy longlegs”
Physical Features
Broad joining of abdomen with cephalothorax without pedicel
Presence of external segmentation of abdomen
4 pairs of long, spindly legs
Legs can regenerate
Ends of chelicerae are pincer-like
Scavenger feeders
Fun Fact: NOT the most poisonous spider. They do not even have venom glands!

33. Order Acari: Ticks & Mites
Habitat: fresh/saltwater, vegetation, ground, parasitic on vertebrates/invertebrates
>25,000 species
Many of which are important to humans
Physical Features
Fused cephalothorax & abdomen (no external tagmatization)
Capitulum- little anterior projections carrying mouthparts

34. MItes Many free living Aquatic species (mostly fresh, some marine)
Dermatophoides farinae live in house dust and cause allergies & dermatoses
Aquatic species (mostly fresh, some marine)
Long, hair-like setae on legs for swimming
Larvae may be parasitic on aquatic inverts
Spider mites (Family Tetranychidae)
Agricultural pests on fruit trees, cotton, clover, etc…

35. Mites Genus Trombicula Genus Demodex
Larvae are called chiggers or redbugs
Feed on dermal tissues of terrestrial vertebrates
Process:
Cause irritating dermatitis
Some species transmit Asiatic scrub typhus
Genus Demodex
Hair-follicle mites

36. Demodex

37. Ticks Genus Ixodes Genus Dermacentor Feeding
Lyme’s Disease
Genus Dermacentor
Rocky Mountain spotted fever
tularemia
Boophilus annulatus (cattle tick)
Texas cattle fever (red-water fever)
Feeding
Pierce skin; suck blood until distended; drop off; digest meal
Molts; feeds again
Disease vectors
Carry protozoans, rickettsial, viral, bacterial, and fungal organisms

38. Subphylum Crustacea
Lobsters, crayfishes, shrimp, crabs, water fleas, copepods, and barnacles

39. Subphylum Crustacea >67,000 species
Primarily aquatic (mainly marine), few terrestrial
Free living; can be sessile, commensal, parasitic
Important to aquatic ecosystems and economy

40. Crustacea: Physical Features
2 pairs of antennae
Mandible and two pairs of maxillae
Typically pair o’ biramous appendages on each segment (except first antennae)
Gills (no malpighian tubules)
16-20 segments (> 60 segments)
Major tagmata: head, thorax, abdomen
Varying degrees of fusion
Carapace- dorsal cuticle of head covers/fuses with some/all thoracic & abdominal segments; clamshell-like vales that cover most/all body; covers entire cephalothorax not abdomen

41. Appendages: Form meets function
Foliaceous
Flat & leaf-like
maxillae
Biramous
2 branches
Swimmerets, maxillipeds, uropods, antennae
Uniramous
1 branch
Walking legs

42. Appendages: Form meets function
Swimmerets- abdominal appendages, biramous
Endopod- inner branch of swimmerets
Exopod- outer branch of swimmerets
Protopod- basal segments, endo/exopods attached to
Maxillipeds- 1st 3 pairs of thoracic appendages
Chelipeds- 1st pair of walking legs enlarged with chela

43. Appendages: Form meets function
Gonopods- 1st pair of abdominal swimmerets used for copulation for males, nursery for eggs/young for females
Uropods- last pair of appendages; paddles for backward movement
Telson- uropods & telson protect young/eggs

44. Body Systems

45. Integumentary Epidermis-endocuticle-exocuticle-epicuticle
Exoskeleton must be molted during maturation and growth
Molting occurs in steps
Old procuticle separates from epidermis, which secretes a new epicuticle
As a new exocuticle is secreted, mottling fluid dissolves old endocuticle, and solution products are reabsorbed
@ ecdysis, the old epicuticle and exocuticle are discarded
In postecdysis, new cuticle is stretched and unfolded and endocuticle is secreted

46. Endocrine Chromatophores Neurosecretory hormones Androgenic glands
Pigments in specialized branched cells
Change color by:
Concentrating pigment granules in center of cells, which causes lightening
Dispersing pigment throughout each cell, which causes darkening
Neurosecretory hormones
Neurosecretory cells in eyestalk control pigment behavior
Hormones control:
Pigment in eyes for light & dark adaptation
Control rate and amplitude of heartbeat
Androgenic glands
Secretions stimulate expression of male sexual characteristics

47. Endocrine Controls molting Molt-inhibiting hormone
created by neurosecretory cells in the X-organ of the eyestalk
released through sinus glands in the eyestalk
Level of hormone decreased
Molting hormone
produced by Y-organs near mandible
Initiates premolt

48. Digestive Mandibles/maxillae involved in ingestion
Maxillipeds hold/crushes food
Suspension feeders
Plankton, detritus, bacteria
Use legs to create water currents that sweep food particles through fringe of setae
Scavengers
Larvae, worms, crustaceans, snails, fishes
Predatory
Lygiosquilla- a walking leg has specialized digit that can be drawn into a groove and released to pierce passing prey
Alpheus- enlarged chela that forms bubble that implodes to stun prey (like cocking a gun)

49. Digestive

50. Digestive Crayfish 2-part stomach
Gastric mill in 1st stomach
Food shredded by mandibles ground by 3 calcareous teeth into fine particles that will pass to 2nd stomach
Particles pass into intestines for chemical digestion

51. Respiration Some small crustaceans breath through body surface Gills
Vary in shape: tree-like, leaf-like, filamentous
Associated blood vessels or sinuses
Attached to appendages usually
Movement through H2O keeps gills ventilated
Branchial chambers
Protected by overlapping carapace

52. Circulatory Open circulatory system Blood Heart (compact or tubular)
Arteries
Movement of organs and limbs circulates blood more effectively in open sinuses than heartbeats and capillaries
Blood
May contain respiratory
pigments
Hemocyanin (decapods)
hemoglobin
Property of clotting to prevent
loss of blood in injuries
transport blood to different areas of hemocoel

53. Excretory Excretory & osmoregulatory organs are paired glands in head
Antennal glands/Maxillary glands/green glands (decapods)- Excretory pores base of antennae or maxillae
Some wastes diffuse through gills as well as excretory glands
Waste products: ammonia with some urea and uric acid

54. Nervous Cerebral ganglion
Located above esophagus
sends nerves to anterior sense organs
Connect to a subesophageal ganglion by a pair of connectives around esophagus
Double ventral nerve cord has a ganglion in each segment that sends nerves to viscera, appendages, & muscles
Giant fiber systems
Sensory organs
Eyes
Statocysts- balance organs
Tactile setae (on cuticle)
Chemosensitive setae (on antennae, antennules, & mouthparts)

55. Nervous- Two types of eyes
Median (nauplius) eyes
2-3 pigment cups containing retinal cells
may have lens
Found in nauplius larvae and in some adults
Compound eyes
can be on moveable eyestalks (i.e. crabs/crayfish)
Detect motion, analyze polarized light
Wide visual field due to convex corneal surface
Composed of ommatidia

56. Nervous: Compound Eye

57. Reproductive Mainly dioecious Most brood their eggs Life Cycles
Barnacles monecious (cross-fertilization)
Parthenogenic in some ostracods
Most brood their eggs
Branchiopods/barnacles- special brood chamber
Copepods- attached egg sacs to abdominal sides
Malacostracans- carry eggs and young attached to appendages
Life Cycles
Crayfish juvenile small version of adult
Most produce larvae that must go through series of changes as it molts
Nauplius- unsegmented body, frontal eye, three pairs of appendages (2 pairs of antennae & mandibles)
Post-larval forms vary among subphyla

58. Life Cycles

60. Subphylum Crustacea Class Branchiopoda Class Maxillopoda
Order Anostraca
Order Notostraca
Order Conchostraca
Order Cladocera
Class Maxillopoda
Subclass Ostracoda
Subclass Copepoda
Subclass Branchiura
Subclass Cirripedia
Class Malacostraca
Order Isopoda
Order Amphipoda
Order Euphasiacea
Order Decapoda

61. Class Branchiopoda Physics Features Reduced 1st antennae 2nd maxillae
Phyllopoda
Flattened, leaf-like legs
Main respiratory organs
Suspension feeding
Locomotion

62. Class Branchiopoda Order Anostraca Order Notostraca Order Conchostraca
Fairy shrimp; brine shrimp
Lack a carapace
Order Notostraca
Tadpole shrimp (i.e. Triops)
Carapace forms large dorsal shield covering most trunk segments
Order Conchostraca
Clam shrimp (i.e. Lynceus)
Bivalved carapace encloses entire body
Order Cladocera
Water fleas (i.e. Daphnia)
Carapace covers body, but not head
Large portion of freshwater zooplankton

63. Class Maxillopoda Physical features: Segmented Telson
5 cephalic, 6 thoracic, 4 abdominal
Telson
Maxillopodan eye in the nauplii

64. Class Maxillopoda Subclass Ostracoda Marine, fresh H2O habitats
Clam-like….bivalved carapace
Several trunk segments fused
# of thoracic appendages reduced to 2 or 0
Burrow in sediments
Scavenge food, feed on detritus, suspension feeding

65. Class Maxillipoda Subclass Copepoda
Free-living in planktonic & benthic habitats (marine & fresh)
10 consumer in many aquatic niches
Many symbiotic, some parasitic
Small, elongate, tapered toward posterior
Lacks carapace
Simple, median, nauplius eye
Appendages
4 pairs of flat, biramous, thoracic swimming appendage
5th pair reduced
No legs on abdomen

66. Class Maxillopoda Subclass Branchiura
Parasitize marine or freshwater fish
5-10 mm long
Physical features:
No gills
Broad, shield-like carapace
Compound eyes
4 biramous thoracic appendages for swimming
Short, unsegmented abdomen
2nd maxillae modified as suction cups

67. Class Maxillopoda Subclass Cirripedia Barnacles
Burrowing or parasitic forms
Enclosed shell of calcareous plates
Sessile as adults
Some can attach to substrate by a stalk
Physical features:
Carapace (mantle) surrounds body, secretes calcareous-plated shells
Reduced head
No abdomen
Long thoracic legs
Many-jointed cirri with hair-like setae
Cirri extend through small opening between the plates to filter feed

69. Class Malacostraca Largest class of Crustacea & diverse
Marine & freshwater
Physical features:
8 thoracic segments
6 abdominal segments
Each segment has a pair of appendages

70. Class Malacostraca Order Isopoda Asellus- freshwater
Ligia- sea beaches, rocky shores
Porcellio & Armadillidium- terrestrial under stones or damp places (rollie pollies)
Some parasites of fish or other crustaceans
Physical features:
Dorsoventrally flattened
No carapace
Sessile compound yes
Gills on abdominal appendages

71. Class Malacostraca Order Amphipoda Marine and freshwaters
Orchestria- beach fleas
Physical features:
No carapace
Sessile compound eyes
Compressed laterally
gills on thoracic segments

72. Class Malacostraca Order Euphausiacea
Important as oceanic plankton- “krill”
Uber important in ocean ecosystems
3-6 cm long
Eaten by baleen whales and many fishes

73. Class malacostraca Order Decopoda Lobsters, crayfish, shrimps, crabs
Physical features:
5 pairs of walking legs
First pair of legs modified to form chelae
True crabs have broader carapace & reduced abdomen

74. Class Malacostraca Order Decapoda: Crabs
Ura (fiddler crabs) – burrow in sand just below high-tide
Decorator crabs- cover carapace with sponges and sea anemones as camouflage
Libinia (hermit crabs)- live in snail shell; abdomen not protected by exoskeleton

75. Centipedes, millipedes
Subphylum Myriapoda
Centipedes, millipedes

76. Subphylum Myriapoda 2 tagmata: head & trunk One pair of antennae
Mandibles & 2 pairs of maxillae (1 pair in millipedes)
Uniramous legs
Respiratory system: respiratory exchange through body surface and tracheael systems (aquatic juveniles may have gills)

77. Subphylum Myriapoda Class chilopoda
Centipedes
Predators- earthworms, insects
Dioecious & oviparous
Physical features:
Somewhat flattened dorsoventrally
Can have up to 177 segments
Segments bear one pair of appendages
First body segment- modified- venom claws
Head with pair of eyes
Respiration- tracheal tubes with pair of each segment

78. Class Chilopoda Scutigera Scolopendra 15 pairs of legs

79. Subphylum Myriapoda Class Diplopoda
“double footed”
Millipedes- “thousand feet”
Herbivorous
Females lay eggs in nest and guards it
Physical features
segments
4 thoracic segments- 1 pair of legs
Abdominal segments
2 pairs of legs on each
2 pairs of spiracles on each
Larva have 1 pair of legs per segment