Activation of Defense Mechanisms in the Nudibranchs Peltodoris nobilis and Hermissenda crassicornis
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Date
2022
Authors
Joy, Siena
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Nudibranchs (“sea slugs”) are marine invertebrates (Phylum Mollusca, Class Gastropoda) that use various chemical defenses to deter predators. Peltodoris nobilis is a member of the superfamily Doridoidea and uses de novo chemical synthesis, converting simple molecules into complex molecules, for defense. Hermissenda crassicornis is a member of the superfamily Aeolidioidea and uses nematocyst sequestration, the storage and firing of nematocysts obtained from prey, for defense. Past research explains the function and evolution of defenses in nudibranchs; however, it is unknown if these defenses are active or passive. Active defense mechanisms are voluntarily activated in response to the environment while passive defense mechanisms are constantly functional. The goal of this research was to determine if the defense mechanisms in P. nobilis and H. crassicornis are active or passive, and if one method is more effective, or works better, at preventing predation than the other. It was hypothesized that the activation of defense mechanisms in both nudibranch species was active and that the defenses were equally effective at preventing predation. This hypothesis was tested by comparing the contact times of a juvenile Glebocarcinus oregonensis crab with an anesthetized and non-anesthetized (control) nudibranch. There was no statistical difference in the crab contact times between the anesthetized and control P. nobilis nudibranchs, however the anesthetized H. crassicornis contact times with the crabs were statistically higher than the control. This suggests that the release of chemicals produced de novo in P. nobilis is passive while the firing of sequestered nematocyst by H. crassicornis is active. Results indicated that the control H. crassicornis contact times with the crabs were statistically lower than P. nobilis. Based on the initial experimental design, this suggests that nematocyst sequestration is more effective at preventing predation. However, the crabs demonstrated little predatory behavior, or attempt to harm, the P. nobilis when in contact, so this study cannot conclusively determine which defense mechanism is more effective at actually preventing predation.
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Keywords
Dorids, Aeolids, Nematocyst Sequestration, de novo chemical synthesis, defense mechanisms