Video on Crayfish Anatomy and Dissection

External Anatomy:

http://www.youtube.com/watch?v=rZ-7LF5AkGs


Internal Anatomy and dissection:

http://www.youtube.com/watch?v=rpkiNLhCBMU&feature=related

Bibliography

Ball, F. (2007, April 19). Crayfish. Retrieved from http://www.anapsid.org/crayfish.html

Biology, H. M. Crayfish Observation and Dissection.

Taxonomy. (96, March 13). Retrieved October 12, 2009, from fwie.fw.vt.: http://fwie.fw.vt.edu/WWW/esis/lists/e454002.htm

The Crayfish Corner. (n.d.). Retrieved October 12, 2009, from Mackers: http://www.mackers.com/crayfish/

Conclusion

This project was very intresting because we learned, not only about our own organism's anatomy but of others. This project also gives us an understanding of the anatomy and physiology of the organisms we worked with. This also showed us how we can compare ourselves (human beings) with animals and that we are not all the same. It was thought in early years that we humans were the same as animals and now we can see for ourselves that we are not.

About the Crayfish

1.Taxonomy:

• Kingdom: Animal - It has to hunt for it's food.
• Phylum: Arthropoda- Has an exoskeleton, segmented body and jointed attachments (appendages).
• Order:Decapoda-"ten footed" 5 pairs of walking legs.
• Group: Crustacean- Their body has a chitinous exoskeleton (similar material to your finger nails), gills, two pairs of antennas and a pair of maxillae and mandibles.
• Class: Crustacea- Have dorsal hearts.
• Family: Cambaridae- Largest of the three family of fresh water Crayfish.
• Scientific Name: Procambarus Clarkii.

2. About the Crayfish

• They have dorsal hearts.
• They have three small mouthparts originating from the head to the rostrum: the mandible, two pairs of maxilae and the maxillipeds that arise from the thorax in the region nearest to the mouth which work as touch sensors.
• Crayfish contain five pairs of walking legs, which is why they are decapoda.
• In the cephalothorax you can find the nervous system, circulatory system, digestive system, reproductive system, and excretory system.
• Under the abdomen are the swimmerets. Which are used for swimming and on male crayfish are used as sperm conductors.
• The abdomen is used for rapid swimming but, they swim backwards. In the female, the abdomen is used for carrying it's eggs.
• There are more than 500 species of crayfish.
• Most of the crayfish live in fresh water.
• When crayfish shed their exoskeleton they are exposed to predator attacks.
• The crayfish has bilateral symetry (When you do a transversal plane you have the same on each side, foe example: legs, eyes, chelipeds, etc.)
• The crayfish are omnivorous, meaning they will eat anything from plants to other fish.

Procedure for Dissection

• Place the crayfish with its dorsal side up in a dissection tray. Locate the cephalothorax and the abdomen. The carapace, a shield of chitin, covers the dorsal surface of the cephalothorax. On the carapace, observe an indentation, the cervical groove, that extends across the midregion and separates the head and thoracic regions. On the thoracic region, locate the prominent structure or indentation on the cephalothorax that defines a central area separate from the sides. Note the individual segments of the abdomen.

• Turn the crayfish on its side, and locate the rostrum, which is the pointed extension of the carapace at the head of the animal. Beneath the rostrum locate the two eyes. Notice that each eye is at the end of a stalk.


• Locate the five pairs of appendages on the head region. First locate the antennules in the most anterior segment. Behind them observe the much longer pair of antennae.
  
• Locate the mouth. Then observe the mandibles, or true jaws, behind the antennae. Now locate the two pairs of maxillae, which are the last appendages in the cephalic region.


• On the thoracic portion of the cephalothorax, observe the three pointed maxillipeds.


• Next observe the largest prominent pair of appendages, the chelipeds, or claws. Behind the chelipeds locate the four pairs of walking legs, one pair on each segment.


• Now use the walking legs to determine the sex of your specimen. Locate the base segment of each pair of walking legs. The base segment is where the leg attaches to the body. Use a magnifying glass to study the inside surface of the base segment of the third pair of walking legs. If you observe a crescent-shaped slit, you have located a genital pore of a female. In a male, the sperm duct openings are on the base segment of the fourth pair of walking legs. Use a magnifying glass to observe the opening of a genital pore.

• On the abdomen, observe the six distinct segments. On each of the first five segments, observe a pair of swimmerets.


• On the last abdominal segment, observe a pair of pointed appendages modified into a pair of uropods. In the middle of the uropods, locate the triangular-shaped telson.


• Now turn the crayfish ventral side up. Observe the location of each pair of appendages from the ventral side.


• Using one hand to hold the crayfish dorsal side up in the dissecting tray, use scissors to carefully cut through the back of the carapace along dissection cut line 1. Cut along the indentations that separate the thoracic portion of the carapace into three regions. Start the cut at the posterior edges of the carapace, and extend it along both sides in the cephalic region.

• *Use forceps to carefully lift away the carapace. Be careful not to pull the carapace away too quickly. Such action would disturb or tear the underlying structure.
  
• Place the specimen on its side, with the head facing left, as shown in the diagram below. Using scissors, start cutting at the base of cut line 1. Cut along the side of the crayfish. Extend the cut line forward toward the rostrum (at the top of the head).


• Use forceps to carefully lift away the remaining parts of the carapace, exposing the underlying gills and other organs.

• Identify the organs of the digestive system. Locate the maxillae that pass the pieces of food into the mouth. The food travels down the short esophagus into the stomach. Locate the digestive gland, which produces digestive substances and from which the absorption of nutrients occurs. Undigested material passes into the intestine. Observe that the intestine is attached to the lobed stomach. The undigested material is eliminated from the anus.


• **Locate and identify the organs of the respiratory system. Locate the gills, which are featherlike structures found underneath the carapace and attached to the chelipeds and walking legs. A constant flow of blood to the gills releases carbon dioxide and picks up oxygen.

• 
  

• Use the diagram of the internal anatomy of the crayfish to locate and identify the organs of the circulatory system. Locate the dorsal tubular heart and several arteries. The crayfish has an open circulatory system in which the blood flows from arteries into sinuses, or spaces, in tissues. The blood flows over the gills before returning to the heart.

• Use the same diagram to locate and identify the organs of the nervous system. Find the ventral nerve cord. Locate a ganglion, one of the enlargements of the ventral nerve cord. Locate the dorsal brain, which is located just behind the compound eyes. Note the two large nerves that lead from the brain, around the esophagus, and join the ventral nerve cord.


• Use the same diagram to locate and identify the organs of the excretory system. The blood carries cellular wastes to the disk-like green glands. Locate these organs just in front of the stomach. The green glands excrete waste through pores at the base of each antenna.
  
• Use the diagram once again to locate and identify the organs of the reproductive system. The animal shown in the diagram is a male crayfish. If your specimen is a male, locate the testis. The testis is the long, white organ under the heart and a bit forward. The sperm ducts that carry sperm from the testis open at the fifth walking leg. If your specimen is a female, locate the bi-lobed ovary. It is in the same relative position as the testis, but the ovary appears as a large, reddish mass under the heart. Then locate the short oviducts that extend from near the center of each side of the ovary and open at the third walking leg. Exchange your specimen with a nearby classmate who has a crayfish of the opposite sex. Then study its reproductive system.


• Dispose of your materials according to the directions from your teacher.


• Clean up your work area and wash your hands before leaving the lab.

Taken from: http://www.smithlifescience.com/Crayfishdissection.htm

Procedure

Procedure I

1. Make a list of the instruments in the dissection kit. Place a sticker with the names of the members of the group on the lid of the dissecting tray and on the tray.




2. One student from the group should go to the table where the specimens were distributed.




3. A pamphlet of the dissection of the organism will be handed out. You must use this pamphlet but you cannot remove it from the classroom. This pamphlet serves as a guide for dissection of the body.




4. Since you enter the classroom you will be evaluated as part of the grade of execution of this project.

Procedure II

1. According to the organism that is assigned to you, you should start looking for the complete classification of each animal. (This part will require the use of reference books or the internet).




2. Once you know what your animal will perform the dissection on, follow these steps:
   
   

• Find the anterior and posterior parts of the organism, draw a picture of the organism and point them out. Please inform the teacher your thoughts to make sure that the parts are correct.




• Find the dorsal and ventral parts of the organism.




• Find the appendages.




• Indicate the parts of the organism (Head, thorax, etc.).




• Indicate the symmetry of the organism using lines that represent the planes and the symmetry of the organism.



• Once you complete this part, you may start the dissection.

Procedure III

1. Dissection: To begin your dissection, position your organism in anatomical position facing you. In other words, the ventral part of the organism must be facing upwards and the dorsal part against the tray.



2. Once you have your organism in this postion you should make the use of dissecting needles to keep the organism on the tray.

Materials

• Dissection Kit


• Dissection Tray


• Gloves


• Apron


• Safety Glasses


• Preserved Organism


• Biology Book or other reference


• Computer with internet access


• Plastic Bags to store your organism in the refrigerator


• Colored pencils


• Notebook


• Photocopy