CRAYFISH LAB

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CRAYFISH LAB

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:MR.FOX'S CRAYFISH LAB
The purpose of this lab activity is to help you learn the anatomy of a crayfish and give you a better understanding of the anatomy of invertebrate animals in general.

After completing this dissection, you should be able to:

1.)Correctly identify the locations involved in the dissection procedures, and

2.)Correctly identify the locations of the major organs within the body of a crayfish.

Materials:

Preserved crayfish

Dissection Pan

Dissection kit
Scalpel
Forceps
Scissors
Dissecting Pins
Probes

Table of Contents:

I.) Setup for the Dissection

II.) External Anatomy
a.) Head
b.) Cephalothorax
c.) Abdomen
d.) Rostrum
e.) Carapce
f.) Compound Eyes
g.) Antennules
h.) Antennae
i.) Walking Legs
j.) Cheliped
k.) Swimmerets
l.) Telson
m.) Uropod
n.) Mouth

III.) Respiratory System
a.) Gills

IV.) Muscle System
a.) Extensor
b.) Flexor

V.) Nervous System
a.) Brain

IV.) Circulatory System
a.) Heart

V.) Digestive and Excretory System
a.) Esophagus
b.) Stomach
c.) Intestine
d.) Anus
e.) Green Gland

VI.) Male Anatomy
a.) Testes

VII.) Female Anatomy
a.) Ovaries

VIII.) Cleanup
a.) Disposal of crayfish
b.) Clean equipment

PAGE 1

I.) External Anatomy

1. Place the preserved crayfish in a dissecting tray.

2. Note that the body of the crayfish is divided into three parts, the head, the cephalothorax and the abdomen.

3. Head - Identify the compound eyes on the rostrum portion of the head.

4. Cephalothorax - Find the Carapace, the covering of the cephalothorax region.

5. Note the larger antennae and smaller antennules protruding from the rostrum.

6. On the ventral side, locate the mouth with the mandibles, or true jaws. The mandibles tear the food, and the other appendages detect and hold food during feeding.

7. There are five pairs of walking legs connected ventrally to the carapace region. The first walking leg has enlarged pincers called chelipeds, and is used to manipulate objects and capture and crush food.

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8. Abdomen - This section is a segmented tail. On the ventral side there are numerous swimmerets. The first pair is modified for the transfer of sperm in those that are ready to mate. Identify the uropod and the telson at the posterior end of the abdomen.

PAGE 2

Respiratory System

1. The gills are located on the outside of the body cavity in a space between the body wall and the carapace. Remove a segment of the carapace on one side of the crayfish to expose them.

2. Detach one of the walking legs, and note the small gill that is attached to the leg.

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PAGE 3

Nervous System

1. Locate a pair of nerves leading from the ventral nerve cord around the esophagus to the large ganglion, or brain, in the head. Short nerves connect the eyes, antennae, and antennules to the brain.

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Circulatory System

1. Locate the diamond shaped heart of the open circulatory system. The heart sends blood into the spaces around the organs through several arteries. After passing through the gills, the blood drains back into the heart through the openings (ostia) in it.

Digestive and Excretory Systems

1. Trace the digestive system from the mouth through the esophagus to the cardiac stomach, where the food is ground up.

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2. From the stomach, food travels to the intestine, where it is absorbed into the blood stream.

3. Next, food waste is expelled through the anus.

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4. Find the green gland located internally just behind each antenna and right under the brain. These structures filter fluid waste from the blood.

Male Anatomy

1. Remove the heart in order to see the gonads (reproductive organs; in males, the testes.) Locate the testes in the male crayfish. Be cautious when trying to find them because they are extremely small.

Anatomy

1. Locate the creamy - yellow ovaries in the female crayfish.