Phylum Arthropoda

1 Phylum Arthropoda

 Defining Characteristics – Epidermis produces a segmented, jointed and hardened chitinous exoskeleton with musculature between individual joints of appendages – Complete loss of motile cilia in adult larval stages

2 Phylum Arthropoda Characters

have segmented bodies with some or all of the segments bearing jointed appendages

 Appendages are specialized for:

3 Phylum Arthropoda Phylum Arthropoda

• “jointed foot” • Largest phylum • 900,000 species – 75% of all known species • Insects, , crustaceans, millipedes, scorpions, ticks, etc. 4 Phylum Arthropoda (cont’d)

• Most successful phylum – Ecologically diverse – Present in all regions of the earth • Adapted to air, land, freshwater, marine, other organisms

5 Reasons for success

1. Versatile exoskeleton 2. Efficient locomotion 3. Air piped directly to cells (terrestrial) 4. Highly developed sensory organs 5. Complex behavior 6. Metamorphosis

6 1. Exoskeleton – External: not enveloped by living tissue – Protection – Secreted by underlying epidermis • Waterproof barrier • Chitin +/- calcium, lipoproteins • Modifications – Can be site for muscle attachment – Energy stores- flying – Sensory receptors – Gas exchange 7 – bristles 1. Exoskeleton (cont’d) – Soft and permeable or hard, impermeable – Between segments of body/appendages= thin + flexible – Must be shed (ecdysis= molting) to allow growth – Relatively heavy • Limits size

8 2. Efficient locomotion – Tagmatization, more specialized than annelids • Regions= tagma/tagmata • Jointed appendages

Crushing food Food handling Drawing water into gills

Touch, taste, food handling 9 Crayfish mouthparts 3. Air piped directly to cells – More efficient than most other invertebrates • Most have efficient tracheal system of air tubes; some breathe by gills • Limits size

10 4. Highly developed sense organs • Sight, touch, smell, hearing, balance, chemical reception

Displacement of seta initiates Eyes convert light energy into a nerve impulse in a receptor nerve impulses cell at its base 11 5. Complex behavior patterns • Complex, organized activities • May be innate (unlearned) or learned

12 6. Limited intraspecific competition – Many arthropods undergo metamorphosis • meta= between/after; morphē= form; osis= state of – Different stages (ie. larva, adult) have different nutrition/habitats  no competition

13 Do these questions now

• What is metamorphosis and why has it contributed to arthropod success? • What phylum is most closely related to Phylum Arthropoda? • Which of the following is not an arthropod? – Beetle – – Clam – Millipede – Caterpillar – leech – elephant 14 Other Characteristics of Arthropods

• Bilateral, triploblastic, schizocoelous • No septa

15 The Wonders of Chitin

• All arthropods have a chitinous jointed exoskeleton • How is this detrimental and beneficial?

16 Phylum Arthropoda Arthropod Segments

• Arthropod segments are grouped into body regions • Some have two regions – Cephalothorax, and abdomen  Some have three regions – Head, thorax, abdomen  Many regions have multiple appendages – Appendages are modified for a particular function

Phylum Arthropoda 17 Arthropod Appendages

• The head usually contains pairs of joint appendages, which are sensory and used in feeding – Antenna’s or feelers are first – Followed by the jaws and mandibles which are used for and chewing • Mandible and accessory mouth parts aid in handling the food and moving it towards the mouth

Phylum Arthropoda 18 Arthropod Appendages Arthropod Vision

• Simple eyes – Light sensitive cells share a common lens • Compound eyes – Thousand of closely packed units called ommatidia

20 Phylum Arthropoda Compound & Simple Eyes

Phylum Arthropoda 21 Digestive system

• Most arthropods have three main regions: foregut, midgut and hindgut

22 Phylum Arthropoda Respiration and Circulatory System

• Extensive surface areas are needed to supply the large oxygen demands of most arthropods – Gills can occur both inside and outside of the of the carapace • Circulatory System – Open circulatory system as in molluscs, hearts vary in structure but do exist – is pumped into empty spaces bathing the tissues in blood Phylum Arthropoda 23 Nervous System and Reproduction

Phylum Arthropoda 24 Arthropod Groups

1. Subphylum Trilobita - extinct trilobites 2. Subphylum – horseshoe crabs, spiders, ticks, mites, and some extinct groups 3. Subphylum Myriapoda – centipedes, millipedes 4. Subphylum Crustacea – crabs, lobsters, shrimps, barnacles 5. Subphylum Hexapoda – Insects 25 Subphylum Trilobita

• tri= three; lobos= lobes • Divided into 3 longitudinal regions • Extinct • Oval, flattened

26 Subphylum Chelicerata

• Horseshoe crabs, spiders, ticks, mites, scorpions

27 Subphylum Chelicerata (cont’d)

• Cephalothorax (prosoma) – Fused head and thoracic region • Abdomen (opisthosoma) – contains digestive, reproductive, excretory, and respiratory organs

28 Subphylum Chelicerata (cont’d)

• Appendages attached to cephalothorax – Pair of chelicerae (clawlike feeding appendages) – Pair of pedipalps (usually sensing or feeding) – four pairs of legs (5 in horseshoe crabs)

29 Subphylum Chelicerata (cont’d)

• No antennae • Most suck liquid food from prey

mite 30 Class Arachnida

• Spiders, ticks, scorpions • Most are predaceous

Scorpion

31 Class Arachnida (cont’d)

• Most are harmless/beneficial to humans

32 Class Arachnida (cont’d)

• Some spiders (ie. black widow, ) give painful, dangerous bites

Brown recluse Black widow 33 Class Arachnida (cont’d)

• Scorpion sting can be painful, dangerous

Scorpion 34 Class Arachnida (cont’d)

• Some ticks and mites spread disease, cause irritation

Dust mite mite 35 Class Arachnida (cont’d)

• – Caused by tick

tick

36 More on spiders…… Order Araneae

37 Spiders

• cephalothorax and abdomen shows no external segmentation – tagma are joined by a narrow pedicel

38 Spiders (cont’d)

• All predaceous – Mostly insects • Chelicerae have fangs

39 Prey capture among the spiders

• Some species are cursorial predators – stalk and ambush their prey – they usually have well- developed eyes

40 Jumping spider Prey capture among the spiders (cont’d)

• Some are web-building spiders – Eyes not as well developed – sensory hairs for detecting vibrations

Grass spider

41 • Many spiders (and mites) producing silk – Used for trapping prey, building nests, forming egg cases

42 43 Orb web construction • silk glands that open to the exterior part of the abdomen through spinnerets

spinnerets

44 Spiders (cont’d)

• Many species have evolved poison glands associated with the chelicerae

Brown recluse Black widow 45 • Spider is used to subdue prey • Venom liquifies tissues with a digestive fluid • Spider sucks up soupy prey (ewwww!)

Wolf spider 46 Urban legends

Debunked!

47 • MYTH: Daddy longlegs (Harvestmen) are one of the most poisonous spiders but their fangs are too short to bite humans: MYTH (!!!!!!!) • Daddy longlegs: Order Opilionid • Spiders: Order Araneae • One basic body segment (no pedicel) • Don’t produce silk • No venom, fangs

48 daddy longlegs Spiders: Class Araneae

Spider love….. • Spiders, like most arthropods, are dioecious • Mating habits – Pheromones- chemicals that elicit behavioral change – Rituals- males pluck female’s web (pattern is species-specific)

49 Spiders: Class Araneae

• Male builds small web, deposits sperm – Collects sperm in cavities of pedipalps – Pedipalps have ejaculatory duct + embolus – inserts pedipalps into female genital opening

50 Spiders: Class Araneae

• Eggs laid in silk case – Carried, attach to web, bury

Wolf spider preparing egg sac 51 A lycosid (wolf spider) preparing egg sac

M. C. Barnhart52 M. C. Barnhart53 M. C. Barnhart 54 M. C. Barnhart55 Wolf spider parental care- after the eggs hatch, the young ride on mom for several days.

56 • Young spiders disperse by silk lines ()

57 Brown recluse

• Violin-shaped stripe on back • Necrotoxin – hemolytic

58 Loxosceles reclusa

• of tissue

59 Day 3

60 Day 4

61 Day 5

62 Day 6

63 Day 9

64 Day 10

65 Crustaceans

66 The Crustaceans lobsters • Phylum Arthropoda – Subphylum Crustacea • crusta= shell • Lobster, crayfish, shrimp, crab, water Daphnia

flea, barnacles shrimp crabs

amphipods

euphausids (krill) amphipods 67 The Crustaceans (cont’d) lobsters

• Aquatic (mostly marine) – a few terrestrial forms • Major ecological and economical importance.

shrimp

euphausids (krill) amphipods 68 • Biramous appendages (at least primitively) – 2 main branches

69 • Only arthropods with 2 pairs of antennae

70 • Great specialization of appendages – Mouthparts chewing, grinding, handling

71 – appendages strengthened for walking or protection (chelipeds, pincer-like claws)

cheliped

walking legs

72 Do these questions now…

• List 3 differences between organisms of Subphylum Celicerata and Subphylum Crustacea • List 4 organisms that are crustaceans

73 • Like other arthropods (+ unlike annelids), coelom is highly reduced • Major body cavity is hemocoel (contains colorless blood)

74 Respiration – gills (usually)

75 • Compound eye is typical of phylum

76 What’s the difference between a crayfish and a lobster?

• Same Order, but different families • Lobsters are bigger • Lobsters are marine; crayfish live in freshwater creeks, ditches, or lakes

77 crayfish lobster Brine Shrimp (Artemia salina) • cosmopolitan • restricted to highly saline lakes and evaporation basins • Dormant cysts= encased embryo 78 Barnacles

“nothing more than a little shrimplike standing on its head in a limestone house and kicking food into its mouth” -Louis Agassiz

79 Barnacles

• living and nonliving substrates • most species secrete CaCO3 shell • Head reduced, rudimentary abdomen

80 Krill

• Component of plankton • Major food for whales

81