Name: ______________________________________________________________ Period:___________
EXTERNAL ANATOMY OF THE
CRAYFISH
PRE-LAB QUESTIONS:
1. Crayfish belong to the Kingdom _Animalia_, the Phylum _Arthropoda_ and the
subphylum __Crustacea_.
2. List three characteristics that all arthropods share.
a. _Exoskeleton_
b. ___Jointed Appendages___
c. __Segmented bodies___
d. Open circulatory system
3. Name two other animals in the same phylum as a crayfish.
a. ___Shrimp, lobsters, barnacles, crabs____
b. _____________________
EXTERNAL ANATOMY:
4. Locate the 1st, 2nd, and 3rd MAXILLIPEDS. These appendages are used for manipulating
food. (The 3rd maxilliped is the largest and topmost one, the 2nd is underneath, and the
1st is underneath the 2nd)
5. Locate the MANDIBLE (jaw) which lies underneath the maxillipeds. This structure
should be hard and difficult to move. What difference do you notice between the
crayfish and the human jaw?
___________________________________________________
6. Locate the two large antennae and the smaller antennules that branch from the base.
The ANTENNAE are sense organs (touch, taste, balance)
7. Locate the EYES, which extend from two stalks called pedicles.
8. The body of the crayfish consists of a cephalothorax (fused head and thorax). The
cephalothorax is encased in an armor called a CARAPACE.
9. Remember that arthropods have a segmented body, bend the crayfish and notice it
bend between the abdomen and the cephalothorax.
10. Locate the CHELIPEDS (the claws). Gently manipulate the cheliped to determine the
direction in which the appendage can bend. How many joints are on a single cheliped?
____________
Name: ______________________________________________________________ Period:___________
11. Cut the end of the cheliped off and use the forceps to find the connective tissue inside.
Pulling on this tissue will make the claw open and close. TRY IT!!
12. Behind the cheliped are four pairs of WALKING LEGS. How many joints are on each
leg? ____________
13. Locate the SWIMMERETS (appendages attached to each segment of the abdomen).
Are the swimmerets jointed? ____ How many pairs of swimmerets are there? ___
14. The last segment of the abdomen (7th segment) is called the telson, and it is specialized
for swimming. Locate the two UROPODS (on the outside of tail); these are two muscles
that allow the crayfish to swim backwards.
15. Determine the gender of your crayfish by looking at the first pair of swimmerets. If
these swimmerets are much larger and stiffer than the other swimmerets, than
CONGRATULATIONS, you have a MALE. If the swimmerets are about the same size as
the others, CONGRATULATIONS, you have a FEMALE. Gender:_____
Label the external structures on the crayfish below:
WORD BANK:
ABDOMEN
MAXILLIPED
SWIMMERETS
UROPOD
WALKING LEGS
CEPHALOTHORAX
EYES
ANTENNAE
CEPHALOTHORAX
ABDOMEN
EYES
SWIMMERETS
MAXILLEPEDS
UROPOD
CHELIPED
ANTENNAE
WALKING LEGS
CHELIPED
Name: ______________________________________________________________ Period:___________
INTERNAL ANATOMY OF THE CRAYFISH
1. Place the crayfish in the dissecting pan on its belly (dorsal side up – back is up).
2. Insert the point of the scissors under the top of the carapace at the back of the
cephalothorax and cut up towards the eyes, stopping when you are between the eyes.
3. Cut across the carapace behind the eyes, and remove the two pieces of carapace.
4. Look at the feathery structures. These are the GILLS. The gills remove oxygen from
the water and put it in the crayfish bloodstream, through the process of DIFFUSION.
5. Remove the gills and legs attached to the thorax. Carefully separate the dorsal layer of
muscles in the thorax and look at the light colored HEART.
6. Remove the heart, and notice the two light colored masses on each side of the body.
These are the DIGESTIVE GLANDS.
7. Between the digestive glands are the reproductive organs (usually white in color). If
you have a female, you may notice a large dark mass of eggs.
8. Locate the INTESTINE by taking your scissors and cutting the shell of the abdomen
back toward the telson (tail). Spread the shell, and the intestine will be found as a tube
on the top side of the muscles of the abdomen. Follow the intestine down to the end of
the crayfish (towards the telson and uropods) and you will find the ANUS.
9. Trace the intestine forward to the point where it joins a large thin walled organ, the
STOMACH. This should be in the front of the cephalothorax.
10. Cut out the stomach and open it up with your scissors, you will find the GASTRIC MILL.
3 ‘teeth’ that aid in digesting the food.
11. Once the stomach is removed, you should be able to see the GREEN GLANDS (kidneys)
located in the head of the crayfish.
12. If you cut between the eyes, you will notice a small mass of white tissue, the BRAIN.
Name: ______________________________________________________________ Period:___________
LABEL THE INTERNAL STRUCTURES OF THE CRAYFISH
WORD BANK:
HEART
BRAIN
GREEN GLANDS
INTESTINE
STOMACH
ANUS
REPRODUCTIVE ORGANS
6. STOMACH
5. BRAIN
1.
HEART
2. INTESTINE
7. REPRODUCTIVE
ORGANS
4. GREEN GLANDS
3. ANUS
Name: ______________________________________________________________ Period:___________
Crayfish Anatomy & Function
“How do crayfish move/protect themselves?”
Carapace
________
A. Organs which help crayfish visualize food and escape predators.
Walking legs
________
B. Large bumpy covering over the thorax used for protection.
Abdomen
________
C. Help the crayfish touch and taste.
Swimmerets
________
D. Broad flat plates which form a paddle to move crayfish backward quickly .
Eye
________
E. Appendages with small pinchers which allow crayfish to walk/move around.
Antennae
________
G. The muscular posterior end which propels the crayfish backward.
Uropod
________
H. Small appendages on abdomen which aid in the reproduction &
development of crayfish
“How do crayfish eat/digest?”
Cheliped
________
A. Sturdy jaws around the mouth used for chewing
Mandible
________
B. Second set of internal ‘teeth’ used to grind food in stomach
Mouth
________
C. Large claws used to catch and break apart food and fight other crayfish.
Stomach
________
D. Pumps body fluid around inside of crayfish to circulate oxygen and nutrients.
Gastric Mill
________
E. Large organ which stores and digests food.
Gills
________
F. Opening which allows crayfish to ingest food.
Heart
________
G. Organ which helps crayfish breathe.
“How do crayfish excrete their waste?”
Green gland
________
A. Long tube which absorbs nutrients from food passed from stomach.
Intestine
________
B. Small opening used to excrete solid waste.
C. Organ which produces bile (digestion) and filters out waste from body fluids.
D. Functions as a crayfish bladder/kidney used to excrete liquid waste.
Name: ______________________________________________________________ Period:___________
Anus
________
Liver
________