Purpose
To observe and sketch the structure and parts of Cnidarians.
Materials
Live hydra specimin if avaliable. In this lab, they weren't.
Microscope
Nematocyst, medusa, Hydra, and Obelia colony slides
Portugese man-O-war specimin
Blank paper and pencil
Microscope
Nematocyst, medusa, Hydra, and Obelia colony slides
Portugese man-O-war specimin
Blank paper and pencil
Method
1. Draw the live Hydra specimin if available; if not, draw and label a Hydra from a slide.
2. Draw and lable the nematocyst.
3. Draw and lable the Obelia colony.
4. Draw the Obelia medusa.
5. Observe the Portugese Man-O-War specimine.
2. Draw and lable the nematocyst.
3. Draw and lable the Obelia colony.
4. Draw the Obelia medusa.
5. Observe the Portugese Man-O-War specimine.
Results
Analysis
1. Q: What life cycle do Cnidarians display and what is the function of each "generation" within the life cycle?
A: Cnidarians display the alternation of generation life cycle. The two generations are polyp, which are sesile, and medusa, which are motile. During the polyp stage, the Cnidarian is attatched to the sea floor. It consumes food using feeding polyps, and new jellyfish are creaded in the reproductive polyps using asexual budding. The jellyfish formed in the polyp are in the medusa stage, and are released when a change in the environment around the polyp occurs. These medusa jellies grow into mature jellyfish. Large groups of jellyfish then form, and all release sperm and eggs into the ocean. The eggs become fertilized, become plantula larvae, and eventually attatch to the sea floor and grow into new polyps.
2. Q: What is the difference between a cnidocyte and a nematocyst?
A: The cnidocytes are microscopic cavities located all along the tenticles of a medusa jellyfish. Each cavity contain deadly venom, as well as a nematocyst. Nematocyst are like tiny harpoons, attatched to the venom sac in the cnidocyte with a very thin, but long tube.
3. Q: How does a nematocyst fire?
A: On the outside of each cnidocyte there is a trigger. When a victim swims past the tenticles of a medusa jellyfish, it hits the triggers of thousands of cnidocytes. The door on the front of the cavity opens, and the nematocyst is shot out at immense speed. The nematocyst bury themselves into the flesh of the victim, just like a harpoon. Venom from the cnidocyte then travels through the tube connected to the nematocyst and into the victim. Depending on the severity of the attack and the species of jellyfish, the stings can cause anything from the slightest tingle to paralysis and even death.
4. Q: In Obelia, describe the role of each type of polup and the medusa.
A: Feeding polyp - Captures and digests food, spreading nutrients throughout the polyp.
Reproductive polyp - Produces medusa jellies asexually by budding from a central stalk in the polyp, and releases jellies during any environmental pressures on the polyp.
Medusa - Reproduces sexually with other jellies once out of the polyp to form new larvae and polyps. Used mainly for species dispersal.
5. Q: How is the Portugese Man-O-War similar and different to Hydra and Obelia?
A: Both the Man-O-War and the Hydra and Obelia belong to the phylum Cnidaria, and reproduce both sexually and asexually. They also have similar tenticles on feeding polyps and identicle digestive systems. However, the Man-O-War is medusa stage dominant and mainly produces sexually, while the Obelia is polyp stage dominant and mainly produces asexually.
A: Cnidarians display the alternation of generation life cycle. The two generations are polyp, which are sesile, and medusa, which are motile. During the polyp stage, the Cnidarian is attatched to the sea floor. It consumes food using feeding polyps, and new jellyfish are creaded in the reproductive polyps using asexual budding. The jellyfish formed in the polyp are in the medusa stage, and are released when a change in the environment around the polyp occurs. These medusa jellies grow into mature jellyfish. Large groups of jellyfish then form, and all release sperm and eggs into the ocean. The eggs become fertilized, become plantula larvae, and eventually attatch to the sea floor and grow into new polyps.
2. Q: What is the difference between a cnidocyte and a nematocyst?
A: The cnidocytes are microscopic cavities located all along the tenticles of a medusa jellyfish. Each cavity contain deadly venom, as well as a nematocyst. Nematocyst are like tiny harpoons, attatched to the venom sac in the cnidocyte with a very thin, but long tube.
3. Q: How does a nematocyst fire?
A: On the outside of each cnidocyte there is a trigger. When a victim swims past the tenticles of a medusa jellyfish, it hits the triggers of thousands of cnidocytes. The door on the front of the cavity opens, and the nematocyst is shot out at immense speed. The nematocyst bury themselves into the flesh of the victim, just like a harpoon. Venom from the cnidocyte then travels through the tube connected to the nematocyst and into the victim. Depending on the severity of the attack and the species of jellyfish, the stings can cause anything from the slightest tingle to paralysis and even death.
4. Q: In Obelia, describe the role of each type of polup and the medusa.
A: Feeding polyp - Captures and digests food, spreading nutrients throughout the polyp.
Reproductive polyp - Produces medusa jellies asexually by budding from a central stalk in the polyp, and releases jellies during any environmental pressures on the polyp.
Medusa - Reproduces sexually with other jellies once out of the polyp to form new larvae and polyps. Used mainly for species dispersal.
5. Q: How is the Portugese Man-O-War similar and different to Hydra and Obelia?
A: Both the Man-O-War and the Hydra and Obelia belong to the phylum Cnidaria, and reproduce both sexually and asexually. They also have similar tenticles on feeding polyps and identicle digestive systems. However, the Man-O-War is medusa stage dominant and mainly produces sexually, while the Obelia is polyp stage dominant and mainly produces asexually.