Cnidarians are predators that use specialized stinging cells to produce cnidocysts. Cnidocysts are membrane-bound organelles consisting of a capsule and an eversible tubule. Cnidocysts are produced and employed for prey capture, defense, and attachment to substrates. Discharge of cnidocytes is regulated by mechanoreceptors called hair bundles. Hair bundles arise from hair cells and are used to detect vibrations from prey to maximize cnidocyst discharge for prey capture. Sea anemones are cnidarians that often live in tightly packed spaces on hard substrates. They often interact with individuals who they recognize as self (clone or conspecific) and non-self (interspecific) by coming into contact with tentacles or body columns of these individuals. The sea anemone can aggressively or passively interact with neighboring anemones by discharging cnidocyst or by employing other effector responses, largely depending on self/non-self recognition. In Chapter 2, experimental results indicate nematocyst discharge, spirocyst discharge, and tentacle contraction are depressed when compared to controls when sea anemones are exposed to conspecific stimuli. Furthermore, nematocyst discharge, spirocyst discharge, and tentacle contraction are enhanced compared to control responses when sea anemones are exposed to interspecific stimuli.
Changes that corals undergo as a result of coral bleaching are important to understand. A sea anemone is used as a model to understand these changes. In Chapter 3, experimental results show the changes to the cnidom in sea anemones that occur as a result of bleaching (becoming aposymbiotic). Aposymbiotic anemones have fewer and smaller penetrant type cnidocysts. Also, these changes were rescued to symbiotic levels when aposymbiotic anemones were supplemented with maximal nutrition. These data indicate that the cnidom is dependent on nutritional availability in aposymbiotic anemones. In Chapter 4, the effects of symbiotic state on prey capture and nematocyst integrity were examined. Aposymbiotic anemones have more, longer hair bundles as compared to symbiotic anemones. Aposymbiotic anemones have fivefold more deformed acontial mastigophores as compared to symbiotic anemones. Aposymbiotic anemones had 30% less prey capture success as compared to symbiotic anemones. Taken together, the results of Chapter 3 and Chapter 4 indicate that the changes observed in aposymbiotic anemone’s cnidom and hair bundle morphology result in a less successful prey capture as compared to symbiotic anemones.
|Advisor:||Watson, Glen M.|
|Commitee:||Chlan, Caryl A., France, Scott C., Greenwood, Paul G., Mire, Patricia L.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||DAI-B 80/08(E), Dissertation Abstracts International|
|Keywords:||Anemone, Cnidae, Cnidarian, Coral bleaching, Nematocyst|
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