1. Subphylum Chelicerata
Horseshoe crabs, spiders, ticks, mites, scorpions

2. Subphylum Chelicerata (cont’d)
Cephalothorax (prosoma)
Fused head and thoracic region
Sensory, feeding, locomotion
Abdomen (opisthosoma)
contains digestive, reproductive, excretory, and respiratory organs
Opistho- behind

3. Subphylum Chelicerata (cont’d)
Appendages attached to cephalothorax
Pair of chelicerae (pincer-like feeding appendages)
Pair of pedipalps (usually sensing or feeding)
four pairs of legs (5 in horseshoe crabs)

4. Subphylum Chelicerata (cont’d)
Usually has eyes
Never has antennae
Most suck liquid food from prey
mite

5. Class Merostomata Two subclasses: Xiphosura (horseshoe crabs)
Covered by carapace
Have chelicerae, pedipalps, 3 pairs walking legs, & 1 pair digging legs
book gills to obtain oxygen from sea water
Euryptida (giant water scorpions) --extinct

6. Class Arachnida Spiders, ticks, scorpions Most are predators
Most harmless to humans
Order Araneae

7. Class Arachnida (cont’d)
Special features to know:
Use coxal glands and/or Malpighian tubules for nitrogenous waste/excretion
Have book lungs (folds of body wall to form lungs)
Air intake tubes: trachaea, which open to outside via spiracles

8. Class Arachnida (cont’d)
Special features to know, continued:
Sensory structures: sensilla
Dioecious (separate male/female individuals)

9. Class Arachnida (cont’d)
Some ticks and mites spread disease, cause irritation
Dust mite
mite

10. Class Arachnida (cont’d)
Lyme disease
Caused by tick
tick

11. Order Scorpionida The Scorpions
Prosoma fused into shield-like carapace
Opisthoma contains digestive & reproductive organs
Oviparous: lay eggs that develop and hatch outside the body
Pedipalps and chelicerae
Posterior stinger
Only a few scorpions are toxic to humans
Found in Northern Africa and Mexico, Arizona, New Mexico

12. Order Araneae (the spiders)
Some spiders (ie. black widow, brown recluse spider) give painful, dangerous bites
Know how to identify them!
Black widow
Brown recluse has “violin”
mark on dorsal side of prosoma
Brown recluse
Black widow has red “hourglass” on
ventral surface of opisthoma

13. Spiders
Prosoma: anterior segment
Opisthoma: posterior segment

14. Spiders (cont’d) All predaceous Chelicerae may have fangs
Mostly insects
Chelicerae may have fangs

15. Prey capture among the spiders
Some species are cursorial predators
stalk and ambush their prey (trap door spider)
they usually have well-developed eyes
Jumping spider

16. Prey capture among the spiders (cont’d)
Some are web-building spiders
Eyes not as well developed
sensory hairs for detecting vibrations
Grass spider

17. Many spiders (and mites) producing silk
Used for trapping prey, building nests, forming egg cases

18. Orb web construction

19. silk glands that open to the exterior part of the abdomen through spinnerets

20. Spider venom is used to subdue prey
Venom liquifies tissues with a digestive fluid
Spider sucks up soupy prey (ewwww!)
Wolf spider

21. 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)

22. 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

23. Spiders: Class Araneae
Eggs laid in silk case
Carried, attach to web, bury
Wolf spider preparing egg sac

24. A lycosid (wolf spider) preparing egg sac
M. C. Barnhart

25. M. C. Barnhart

26. M. C. Barnhart

27. M. C. Barnhart

28. Wolf spider parental care- after the eggs hatch, the young ride on mom for several days.

29. Crustaceans

30. The Crustaceans Phylum Arthropoda
lobsters
Phylum Arthropoda
Subphylum Crustacea
crusta= shell
Lobster, crayfish, shrimp, crab, water flea, barnacles
Daphnia
shrimp
crabs
amphipods
euphausids (krill)
amphipods

31. The Crustaceans (cont’d)
lobsters
Aquatic (mostly marine)
a few terrestrial forms
Major ecological and economical importance.
shrimp
amphipods
euphausids (krill)

32. Biramous appendages (at least primitively)
2 main branches

33. Only arthropods with 2 pairs of antennae

34. Great specialization of appendages
Mouthparts chewing, grinding, handling

35. appendages strengthened for walking or protection (chelipeds, pincer-like claws)
walking legs

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

37. Respiration
gills (usually)

38. Compound eye is typical of phylum

39. 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
lobster
crayfish

40. Brine Shrimp (Artemia salina)
cosmopolitan
restricted to highly saline lakes and evaporation basins
Dormant cysts= encased embryo

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

42. Barnacles living and nonliving substrates
most species secrete CaCO3 shell
Head reduced, rudimentary abdomen

43. Krill Component of plankton Major food for whales
Plankton- small organisms that drift in water