Crayfish are crustaceans in the class Malacostraca. They have a hard exoskeleton made of chitin that they must molt to grow. Their body is segmented with a fused cephalothorax covered by a carapace. They have compound eyes, antennae, walking legs, swimmerets, and a tail fan of uropods and telson. Crayfish have an open circulatory system and breathe through gills that are kept flushed by walking legs and swimmerets. They have a stomach, digestive gland, green glands, nervous system, and reproductive organs that vary by sex.

1. CRAYFISH
DISSECTION

4. Animal Groups
Image from: http://ology.amnh.org/biodiversity/treeoflife/pages/graph.html

5. ARTHROPODA
“Arthro” = jointed
“pod” = foot

6. Arthropods

7. Structures to identify in lab
• All terns in the powerpoint that are printed
in RED.

8. Classifying Crayfish
Kingdom: ANIMALIA
Phylum: ARTHROPODA
Class: CRUSTACEA

9. EXOSKELETON- Outside body; NON-LIVING
Made of CHITIN (polysaccharide with some nitrogen)

10. All animals with an EXOSKELETON
must MOLT (shed their exoskeleton)
to grow bigger

11. SEGMENTED BODY
like earthworms

12. Fusion of smaller segments to make
one bigger section
Head + thorax = cephalothorax

13. CARAPACE
Part of exoskeleton that
covers the cephalothorax

14. CHELIPED = Pincher (defense; capture food)
ROSTRUM = “visor” protects eyes

15. COMPOUND EYE
HAS MULTIPLE LENSES

16. ANTENNAE- touch, taste
ANTENNULES- touch,
taste, & equilibrium

17. Statocyst

18. DECAPODS (10 legs)
(4 pair walking legs + 2 chelipeds)

19. SWIMMERETS (5 pair)

20. SWIMMERETS
Aid in reproduction
In males – transfer sperm
In females – carry eggs/young
Create water currents

21. Telson
Uropods
Uropods Uropods
Telson

22. MAXILLA – Manipulate food

23. LAST PAIR of MAXILLA = “BAILERS”
Keep water moving over gills

24. MANDIBLE

25. Appendages
1. Walking legs
2. Cheliped
3. Maxillipeds
4. 2nd maxilla
(gill bailer)
5. 1st maxilla
6. Mandible
7. Antenna
8. Antennule

26. APPENDAGES
ANTENNA Touch, taste
ANTENNULE Touch, taste, equilibrium
MANDIBLE Chew food
MAXILLA Manipulate food
Last pair “bailers”-
Move water over gills
MAXILLIPEDS Touch, taste, manipulate food
CHELIPED Capture food, defense
WALKING LEGS Locomotion,
move water over gills
SWIMMERETS Move water over EGGS,
transfer sperm (males)
carry young/eggs (females)
UROPOD Propulsion during tailflips

27. Is it a MALE OR FEMALE?
MALES:
first two pair
of swimmerets
form a channel
to transfer
sperm to female
seminal receptacle

28. SWIMMERETS
MALES
Top pair
make a
“V”

29. Females “in berry”
carry developing embryos on swimmerets

30. REPRODUCTIVE
SEPARATE SEXES
Male and Female
EXTERNAL FERTILIZATION
sperm & eggs join outside body
INDIRECT DEVELOPMENT
Starts as a larva

31. INDIRECT DEVELOPMENT
MOLLUSKS ECHINODERMS CRUSTACEANS
TROCHOPHORE BIPINNARIA NAUPLIUS

32. Examine the inside
of your crayfish

33. RESPIRATORY
GILLS (#2) Exchange gases
Remove nitrogen waste (AMMONIA)

35. What keeps water moving over gills?
“BAILERS”
WALKING LEGS:
are attached to gills so walking moves
water
Image from: http://www.aa.psu.edu/div/mns/biology/crayfish/crayfishtable.htm

36. INTERNAL
Heart
Stomach Digestive gland

37. OPEN CIRCULATORY SYSTEM
HEART with openings (OSTIA)
ARTERIES leaving heart but NO VEINS to
return hemolymph

38. OSTIA

39. ADDUCTOR MUSCLES
run mouthparts

40. STOMACH
PYLORIC
CARDIAC

41. GASTRIC MILL
“teeth” inside stomach

42. DIGESTIVE GLAND
Makes bile; finishes digestion; absorbs nutrients

43. GONADS (produces sex cells)

44. Females:
OVARIES – make eggs
SEMINAL RECEPTACLES - store received sperm
Males:
TESTES – make sperm
VAS DEFERENS- tubules inside that carry sperm
from testes to exit opening
ENDOCRINE SYSTEM:
controls sexual development
Also: molting, heart rate

45. ABDOMEN
INTESTINE (#4) – finish digestion; absorb
nutrients; collect & remove feces

46. GREEN GLANDS (#2) - collect and remove excess
water & nitrogen waste (ammonia, NH3)

47. NERVOUS SYSTEM
like earthworms
VENRAL NERVE CORD
CEREBRAL GANGLIA (brain)
GANGLIA along body

48. VENTRAL NERVE CORD

49. CEREBRAL GANGLIA =
BRAIN
Nerves connect
the eyes, antennae,
and antennules
to the brain.

50. Brain
Brain

51. AUTOTOMY &
REGENERATION
Crayfish have the
ability to
“self amputate” parts
to escape predators
and regenerate to
repair injuries

52. THE END