CRAYFISH DISSECTION
Animal Groups
Image from: http://ology.amnh.org/biodiversity/treeoflife/pages/graph.html
ARTHROPODA
“Arthro” = jointed“pod” = foot
Arthropods
Structures to identify in lab
• All terns in the powerpoint that are printed in RED.
Classifying CrayfishKingdom: ANIMALIA Phylum: ARTHROPODAClass: CRUSTACEA
EXOSKELETON- Outside body; NON-LIVING
Made of CHITIN (polysaccharide with some nitrogen)
All animals with an EXOSKELETON must MOLT (shed their exoskeleton)
to grow bigger
SEGMENTED BODYlike earthworms
Fusion of smaller segments to make one bigger section
Head + thorax = cephalothorax
CARAPACE
Part of exoskeleton that covers the cephalothorax
CHELIPED = Pincher (defense; capture food) ROSTRUM = “visor” protects eyes
COMPOUND EYE
HAS MULTIPLE LENSES
ANTENNAE- touch, taste
ANTENNULES- touch, taste, & equilibrium
Statocyst
DECAPODS (10 legs) (4 pair walking legs + 2 chelipeds)
SWIMMERETS (5 pair)
SWIMMERETS
Aid in reproduction
In males – transfer sperm
In females – carry eggs/young Create water currents
TelsonUropods
Telson
UropodsUropods
MAXILLA – Manipulate food
LAST PAIR of MAXILLA = “BAILERS”Keep water moving over gills
MANDIBLE
Appendages1. Walking legs 2. Cheliped 3. Maxillipeds4. 2nd maxilla
(gill bailer)5. 1st maxilla6. Mandible7. Antenna8. Antennule
APPENDAGESANTENNA Touch, tasteANTENNULE Touch, taste, equilibriumMANDIBLE Chew foodMAXILLA Manipulate food
Last pair “bailers”- Move water over gills
MAXILLIPEDS Touch, taste, manipulate foodCHELIPED Capture food, defenseWALKING LEGS Locomotion,
move water over gillsSWIMMERETS Move water over EGGS,
transfer sperm (males) carry young/eggs (females)
UROPOD Propulsion during tailflips
Is it a MALE OR FEMALE? MALES:
first two pair of swimmerets form a channel to transfer sperm to female seminal receptacle
SWIMMERETSMALESTop pair make a “V”
Females “in berry”carry developing embryos on swimmerets
REPRODUCTIVESEPARATE SEXES Male and FemaleEXTERNAL FERTILIZATION sperm & eggs join outside bodyINDIRECT DEVELOPMENT Starts as a larva
INDIRECT DEVELOPMENT
MOLLUSKS ECHINODERMS CRUSTACEANS
TROCHOPHORE BIPINNARIA NAUPLIUS
Examine the inside of your crayfish
GILLS (#2)
RESPIRATORY
Exchange gasesRemove nitrogen waste (AMMONIA)
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
INTERNAL
Heart
Stomach Digestive gland
OPEN CIRCULATORY SYSTEM
HEART with openings (OSTIA)ARTERIES leaving heart but NO VEINS to
return hemolymph
OSTIA
ADDUCTOR MUSCLESrun mouthparts
PYLORIC
CARDIAC
STOMACH
GASTRIC MILL“teeth” inside stomach
DIGESTIVE GLAND
Makes bile; finishes digestion; absorbs nutrients
GONADS (produces sex cells)
Females: OVARIES – make eggsSEMINAL RECEPTACLES - store received sperm
Males:TESTES – make spermVAS DEFERENS- tubules inside that carry sperm
from testes to exit opening
ENDOCRINE SYSTEM:controls sexual development
Also: molting, heart rate
ABDOMENINTESTINE (#4) – finish digestion; absorb
nutrients; collect & remove feces
GREEN GLANDS (#2) - collect and remove excess water & nitrogen waste (ammonia, NH3)
NERVOUS SYSTEMlike earthworms
VENRAL NERVE CORDCEREBRAL GANGLIA (brain)GANGLIA along body
VENTRAL NERVE CORD
CEREBRAL GANGLIA = BRAIN
Nerves connect the eyes, antennae, and antennules to the brain.
Brain
Brain
AUTOTOMY & REGENERATION
Crayfish have the ability to “self amputate” parts to escape predators and regenerate to repair injuries
THE END