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