Grasshopper Dissection
Purpose
To investigate the major internal and external features of the insects
Materials
Dissecting pan
Dissecting kit
Dissecting pins
Grasshopper specimen
Dissecting kit
Dissecting pins
Grasshopper specimen
Method
Part 1: External anatomy
1. Place preserved grasshopper on dissecting pan. Identify the antennae, compound and simple eyes, tympanum, jumping and walking legs, jaws, palps, spiracles, wings, ovipositor or claspers, head, thorax, and abdomen.
2. You can tell the sex of your grasshopper in two ways: Females have an ovipositor which she uses to dig a hole into the ground to deposite their her eggs. Males have small claspers, which are used when mating. Also, when mature, a female grasshopper is twice the size of a male.
3. Carefully remove each mouth piece as instructed in order using your forceps. Remove the labrum (upper lip) by getting forceps under it as far up as possible and then carefully pulling it out. Do NOT rip! Remove the labrium (lower lip) using the same method. Next remove the maxilla, one at a time, together with the sensory palp. The mandibles are next, and are the hardest to get out. Firmly hold the grasshoppers head while pulling on one mandible with the forceps. Do NOT rip the head off! Remove the other mandible in the same fasion. Finally, remove the hypopharynx.
Part 2: Internal anatomy
1. Remove the 3 legs on the grasshopper's left side. Beginning at the posterior-most segment, make a mid-dorsal incision all the way up to the front of the thorax (back of head). Don't cut too deeply, as you could destroy the organs. Cur along the side of the thorax around to the ventral surface. Now open the "flaps". There are usually some muscle attachments that you need to cut away. secure the flaps with pins.
2. The hearts are difficult to see, and may already be destroyed. Posterior to the hearts are the eggs or male gonads. Remove these to expose the digestive system.
3. Locate the mouth and anus. The digestive tract connects these two points. Just after the mouth is the esophagus which leads to the storage crop. The crop connects to the thicker gizzard which helps to grind food. The gizzard leads to the stomach which leads to the intestine and anus. Around the stomach is the gastric caeca which empty enzymes into the stomach.
4. Locate the thin-walled traechids (tubes) that connect internally to the spiracles which are the external openings used to transport air into the grasshopper's tissues. Notice also, in the area of the intestine, the fine thread-like Malpighian Tubules - these are the kidneys.
5. Cut the esophagus and the anus and remove the entire digestive system in one piece. Cut a V shaped notch in the back of the head and remove the neck muscles that extend into the head. In the area between the eyes and antennae inside the head, locate the brain, which appears as a small white mass. Locate the ventral nerve cord connecting to the brain. Follow the cord all the way to the last segment.
4. Locate the thin-walled traechids (tubes) that connect internally to the spiracles which are the external openings used to transport air into the grasshopper's tissues. Notice also, in the area of the intestine, the fine thread-like Malpighian Tubules - these are the kidneys.
5. Cut the esophagus and the anus and remove the entire digestive system in one piece. Cut a V shaped notch in the back of the head and remove the neck muscles that extend into the head. In the area between the eyes and antennae inside the head, locate the brain, which appears as a small white mass. Locate the ventral nerve cord connecting to the brain. Follow the cord all the way to the last segment.
6. Wash all equipment and return to the proper storage place. Dispose of the grasshopper as per your teacher's instructions.
Analysis
1. Q: Label the external features on the diagram below;
A: See first picture
2. Q: The sex of my grasshopper is: _____________. I know this because:
A: My grasshopper is female because it has ovaries on its dorsal side.
3. Q: What is the function of each mouth part?
A: Labrum: Hold food
Labium: Helps the maxilla hold food
Maxilla: Chew and taste food
Mandible: used to pierce and chew food
Hypopharynx: Tongue of the grasshopper, produces saliva
4. Q: Label the internal structures on this female grasshopper:
A: See third and fourth pictures
5. Q: Complete the following table:
A: See first picture
2. Q: The sex of my grasshopper is: _____________. I know this because:
A: My grasshopper is female because it has ovaries on its dorsal side.
3. Q: What is the function of each mouth part?
A: Labrum: Hold food
Labium: Helps the maxilla hold food
Maxilla: Chew and taste food
Mandible: used to pierce and chew food
Hypopharynx: Tongue of the grasshopper, produces saliva
4. Q: Label the internal structures on this female grasshopper:
A: See third and fourth pictures
5. Q: Complete the following table:
CharacteristicNumber of body regions
Is the body segmented? Number of walking legs Number of jumping legs Are the appendages jointed? Type of skeleton Are there fused body regions? Number of antennae Number of wings Type of respiratory system Are the sexes seperate? Location of main nerve cord Type of circulatory system Location of heart Excretory organ |
Grasshopper Equivalent
Three - Head, thorax, and abdomen
Yes Two pairs One pair Yes Exoskeleton Yes - it has a cephalothorax One pair One pair Uses spiracles to bring oxygen into bloodstream Yes Ventral side of body Open circulatory system Just above eggs on dorsal surface Anus |
6. Q: What have you learned from this lab about grasshoppers? About arthropods?
A: I found it very cool that grasshoppers breathe through their sides. It was also cool to dissect something with an exoskeleton. It seems like they would be quite hard, but all the joints in their skin makes them pretty weak. It was also cool to finally dissect something that had a digestive system that somewhat resembled that of a more advanced animal. It was also really, really, creepy to learn that grasshoppers can grow to be that big! Never going outside again....
A: I found it very cool that grasshoppers breathe through their sides. It was also cool to dissect something with an exoskeleton. It seems like they would be quite hard, but all the joints in their skin makes them pretty weak. It was also cool to finally dissect something that had a digestive system that somewhat resembled that of a more advanced animal. It was also really, really, creepy to learn that grasshoppers can grow to be that big! Never going outside again....
Crayfish Dissection
Purpose
To investigate the internal and external structures of the crayfish.
Materials
Crayfish
Dissecting tray
Dissecting kit
Dissecting tray
Dissecting kit
Method - Part 1: External Anatomy
1. Collect a crayfish from your teacher. Rinse off the preservatives and place it in a tray dorsal side up. Examine the hard, chitinous exoskeleton and note that the body of the crayfish is divided into two distinct regions; the cephalothorax and the abdomen. The abdomen ends in the flipper made up of the telson and uropods. You should be able to see the segmentation of the abdomen, but to see it in the cephalothorax, turn the crayfish ventral side up. Each pair of appendages attaches to a different segment.
2. Note all the appendages - count as many pairs as possible, including the antennae and mouth parts. Record this.
3. Examine the walking legs. The anterior most legs are the chelipeds used for defence and obtaining food. Examine the joints along the legs.
4. Examine the swimmerets located along the abdomen's surface. In males, such as the one pictured here, the swimmerets are enlarged into a pseudopenis used to transfer sperm to the female during mating. In females, they hold eggs.
5. Examine the flipper at the end of the abdomen. It is used to make rapid movements backwards away from predators. It is made of the telson and uropods. Locate the anus.
2. Note all the appendages - count as many pairs as possible, including the antennae and mouth parts. Record this.
3. Examine the walking legs. The anterior most legs are the chelipeds used for defence and obtaining food. Examine the joints along the legs.
4. Examine the swimmerets located along the abdomen's surface. In males, such as the one pictured here, the swimmerets are enlarged into a pseudopenis used to transfer sperm to the female during mating. In females, they hold eggs.
5. Examine the flipper at the end of the abdomen. It is used to make rapid movements backwards away from predators. It is made of the telson and uropods. Locate the anus.
6. Turn the crayfish onto its ventral surface. Note the piece of exoskeleton that covers the cephalothorax, called the carapace. The horn shaped beak at the anterior most point of the carapace is called the rostrum. Locate the compound eyes that are beneath the rostrum.
7. Examine the antennae and antennules and then turn the crayfish so the ventral side is up. Locate the mouth.
8. Around the mouth are 6 pairs of appendages; 2 pairs of maxilla, 3 pairs of maxillipeds, and 1 pair of mandibles
Part 2: Internal Anatomy
1. Place crayfish dorsal side up and, using your scissors, cut from the posterior of the carapace up to the base of the rostrum along the mid-point. Cut from the base of the rostrum down, on the left and right, to the ventral surface.
2. Use the scalpel to cut through the thin connective tissue seperating the cephalothorax from the abdomen. Gently pull open the carapace to peek inside to see the muscles. Use the scalpel to cut these muscles from the carapace. Don't cut the organs! Cut along the ventral portion of the carapace until it is completely removed.
3. Remove the walking legs and locate the gills - remove one with scissors, noting the surface area.
4. Seperate the dorsal muscles in the thorax to expose the diamond shaped heart. If you are careful you may see the small blood vessels connecting to it. Remove the heart.
5. Remove the thin sides of the thorax. Doing this will expose the internal organs. There are two chalky masses. The mass that extends from the thorax to the head is the digestive glands. The other, which extends to the posterior, is the reproductive organs. Carefully remove the digestive glands.
2. Use the scalpel to cut through the thin connective tissue seperating the cephalothorax from the abdomen. Gently pull open the carapace to peek inside to see the muscles. Use the scalpel to cut these muscles from the carapace. Don't cut the organs! Cut along the ventral portion of the carapace until it is completely removed.
3. Remove the walking legs and locate the gills - remove one with scissors, noting the surface area.
4. Seperate the dorsal muscles in the thorax to expose the diamond shaped heart. If you are careful you may see the small blood vessels connecting to it. Remove the heart.
5. Remove the thin sides of the thorax. Doing this will expose the internal organs. There are two chalky masses. The mass that extends from the thorax to the head is the digestive glands. The other, which extends to the posterior, is the reproductive organs. Carefully remove the digestive glands.
6. Make a mid-dorsal cut with scissors down the abdomen from the cephalothorax to the telson. Use the scalpel to cut away the connecting muscles and fold the plates back.
7. Remove the reproductive glands, exposing the intestine, which connects the stomach to the anus. Remove the entire digestive system by cutting the esophagus and the lower intestine.
8. Look inside the head along the anterior floor and locate two round brown organs. These are the green glands, which act as kidneys. Leave them in place.
9. Inside the head is a light coloured patch - this is the brain. There are two nerves connecting from the ventral surface of the throrax. These are the ventral nerve cords. Expose the entire nerve cord along the thorax.
10. This leads to the abdomen where the muscles cover the nerve cord. The muscle is the part of the crayfish that we eat. Gently remove the muscle to expose the rest of the nerve cord.
11. Clean all dissecting equipment and dispose of the crayfish.
Analysis
1. Q: How many pairs of appendages did the crayfish have?
A: Thirteen
2. Q: Label the following diagram:
A: See first two pictures in this lab.
3. Q: How do the mouth parts of a crayfish compare to the mouth parts of a grasshopper?
A: While the grasshopper and the crayfish share some similar mouth parts, the crayfish has six pairs while the grasshopper has 4.
4. Q: How does the thickness of the exoskeleton around the joint compare with the thickness around the rest of the leg?
A: The exoskeleton around the majority of the leg is very thick, making up the majority of the leg. The area around the joints has virtually no exoskeleton; mostly just muscles and tendons. This makes the joints much weaker than the rest of the leg.
5. Q: What sex is the crayfish? How do you know?
A: My crayfish is a male. I know this because his swimmeretes form into a pseudopenis used for sperm transfer.
6. Q: Why is there so much surface area on the gills of a crayfish?
A: It makes it more efficient for the crayfish to bring in oxygen as more water can be filtered through the gills.
7. Q: Draw the digestive system and label the structures food would pass through.
A: Food enters through the mouth and travels through the esophagus to the crayfish's stomach. It then enters the intestine, which it travels through the abdomen until the wastes exit through the anus. Metabolic wastes are filtered through the green glands, where water is removed and sent back into the body while the waste is sent out of the body.
A: Thirteen
2. Q: Label the following diagram:
A: See first two pictures in this lab.
3. Q: How do the mouth parts of a crayfish compare to the mouth parts of a grasshopper?
A: While the grasshopper and the crayfish share some similar mouth parts, the crayfish has six pairs while the grasshopper has 4.
4. Q: How does the thickness of the exoskeleton around the joint compare with the thickness around the rest of the leg?
A: The exoskeleton around the majority of the leg is very thick, making up the majority of the leg. The area around the joints has virtually no exoskeleton; mostly just muscles and tendons. This makes the joints much weaker than the rest of the leg.
5. Q: What sex is the crayfish? How do you know?
A: My crayfish is a male. I know this because his swimmeretes form into a pseudopenis used for sperm transfer.
6. Q: Why is there so much surface area on the gills of a crayfish?
A: It makes it more efficient for the crayfish to bring in oxygen as more water can be filtered through the gills.
7. Q: Draw the digestive system and label the structures food would pass through.
A: Food enters through the mouth and travels through the esophagus to the crayfish's stomach. It then enters the intestine, which it travels through the abdomen until the wastes exit through the anus. Metabolic wastes are filtered through the green glands, where water is removed and sent back into the body while the waste is sent out of the body.
8. Q: Which appendage is used to:
A: Sense - Uses compound eye to see like our eyes, simple eye to detect light. Tympanum under legs detect vibrations
Defend - Uses the chelipeds (pinchers) on the front of the body, are modified appendages
Mate - Males use their pseudopenis to release sperm, females swimmeretes are modified to hold eggs
Eat - Use chelipeds to capture food, then eat using its 6 mouth parts
Chew - Maxillipeds tear the food, the maxilla rips the food side to side, and the mandible finished the chewing and moves it into the pharynx
Move backwards - Uses the tail, consisting of a telson and uropods, to propell itself quickly away from predators
Move forewards - Uses legs to walk along the ocean floor
Swim - Uses swimmeretes on the ventral side of its abdomen
9. Q: How are arthropods more advanced than the other phyla we've looked at so far?
A: - Better developed nervous system
- More efficient circulatory and respiratory system with better gills
- First development of a skeleton, in form of exoskeleton
- Ability to fly
- Live on land and water
- Segmented body plan
- More developed appendages for reproductive and defencive purposes
- With all these advances, makes them capable of more activites and better defence against predators
10. Q: Why are the insects so prolific while the crayfish are not?
A: Insects have many traits that crayfish do not. Insects can fly, while crayfish cannot. Insects also have a much greater camoflague ability, which helps them to avoid their predators. They became prolific to begin with as insects were one of the first animals to move onto land, so they had little to no competition to find food and shelter, and virtually no predators. They were also highly adapted to live in the the rapidly changing world. Crayfish, on the other hand, had to survive in the ocean, competing with much older species of animals that have become highly evolved over time, like the jellyfish.
A: Sense - Uses compound eye to see like our eyes, simple eye to detect light. Tympanum under legs detect vibrations
Defend - Uses the chelipeds (pinchers) on the front of the body, are modified appendages
Mate - Males use their pseudopenis to release sperm, females swimmeretes are modified to hold eggs
Eat - Use chelipeds to capture food, then eat using its 6 mouth parts
Chew - Maxillipeds tear the food, the maxilla rips the food side to side, and the mandible finished the chewing and moves it into the pharynx
Move backwards - Uses the tail, consisting of a telson and uropods, to propell itself quickly away from predators
Move forewards - Uses legs to walk along the ocean floor
Swim - Uses swimmeretes on the ventral side of its abdomen
9. Q: How are arthropods more advanced than the other phyla we've looked at so far?
A: - Better developed nervous system
- More efficient circulatory and respiratory system with better gills
- First development of a skeleton, in form of exoskeleton
- Ability to fly
- Live on land and water
- Segmented body plan
- More developed appendages for reproductive and defencive purposes
- With all these advances, makes them capable of more activites and better defence against predators
10. Q: Why are the insects so prolific while the crayfish are not?
A: Insects have many traits that crayfish do not. Insects can fly, while crayfish cannot. Insects also have a much greater camoflague ability, which helps them to avoid their predators. They became prolific to begin with as insects were one of the first animals to move onto land, so they had little to no competition to find food and shelter, and virtually no predators. They were also highly adapted to live in the the rapidly changing world. Crayfish, on the other hand, had to survive in the ocean, competing with much older species of animals that have become highly evolved over time, like the jellyfish.