Olfaction Theory - can
Advanced Search SUMMARY Wandering albatrosses routinely forage over thousands of kilometres of open ocean, but the sensory mechanisms used in the food search itself have not been completely elucidated. As an initial step to test the hypothesis, we carried out behavioural experiments exploring the sensory capabilities of adult wandering albatrosses at a breeding colony. Three two-choice tests were designed to investigate the birds' response to olfactory and visual stimuli, individually or in combination. Our results indicate that birds were able to perceive the three types of stimulus presented: olfactory, visual and combined. Moreover, olfactory and visual cues were found to have additional effects on the exploratory behaviours of males. Procellariiforms use, or have been suggested to use, their sense of smell in various behaviours including foraging Hutchison and Wenzel, , homing Bonadonna et al. Following Grubb's pioneering experiments Grubb, , most of the early work investigated sensitivity to food-related scents by exposing wild seabirds to odorous stimuli such as cod liver oil-soaked sponges Jouventin and Robin, ; Lequette et al. These experiments provided an extensive list of procellariiform species for which olfactory foraging was supported, including storm petrels Oceanites oceanicus, Oceanodroma leucorhoa , petrels Pagodroma nivea, Macronectes giganteus, Daption capense, Procellaria aequinoctialis , shearwaters Puffinus gravis, P. The wandering albatross Diomedea exulans, Diomedeidae, Linnaeus is the largest of the procellariiform seabirds and has the largest wingspan of any living bird. Olfaction Theory
Credit: Wikimedia Commons Olfaction is one of the most important senses.
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It protects us from eating spoiled food, it helps animals Olfaction Theory detect their relatives, it makes the perfume business quite successful and, in general, it connects us to the Olfaction Theory chemicals surrounding us. How this detection, and identification, takes place is a question that is still under debate, and recently new experimental data have been released.
The main theory about olfaction states that the electronic shape of the molecule allows them to activate certain receptors of the olfactory system. This is usually referred as the shape theory. In contrast, R. H Wright proposed a second theory in called the vibrational theory. This second theory was largely abandoned until, inLuca Turin proposed a concrete mechanism about how Olfaction Theory could work 1. In this paper Turin speculated with the possibility of some receptors measuring molecular vibrations together with the electronic shape. The vibrational theory of olfaction was first tested in an experimental way by a psychophysical experiment 2.
In this experiment researchers prepared some molecules with the same electronic shape, but different vibrational behavior. One of the molecules used was acetophenone AP. Hence, in order to change the vibrational component they prepared also deuterated acetophenone AP-d8.
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That new molecule is equal to the regular one, but some of the atoms have been replaced by isotopes, with different number of neutrons. That makes a strong difference in the nuclei without affecting the electronic Olfaction Theory of the molecule.
Then, they told people to distinguish both components by smelling. Some of the results are summarized in Figure 2. Figure 2. Refer to the Olfaction Theory for an explanation. The experiment was performed under a double-blind Olfaction Theory where neither the subjects nor the test administrator knew which odorant was in the vial. In a the question was to classify the differences between the odors. They made different trials where sometimes both components were the same and Olfactikn other they were different.
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Olfaction Theory The results show that the differences Thepry not Olfaction Theory when the subjects smell the regular and deuterated acetophenone than when both vials contained the same component. In experiment b the purpose was to distinguish both components from different vials, in c to distinguish from three samples two of which were equal, and in d the results for different concentration of both components are displayed. The results are clear, humans cannot distinguish AP from AP-d8 by smelling, even if their vibrational energies are very different. Does this mean that this theory should be rejected? Not yet.
Biological and psychophysical tests are complicated and they should be performed in different ways. Furthermore, recently new experiments have Olfaction Theory performed 3now involving fruit flies, and the results point into a complete different direction. In this experiment flies where trained, by electrical shocks, to avoid one of the components.
Some of the results are displayed in Figure 3. Figure 3.
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Credit: M. Different deuterated molecules where used, and the flies could distinguish them note that in this paper ADP represents acetophenone, that was Olfaction Theory as AP in the previous one. In conclusion, flies can distinguish between deuterated and not deuterated molecules. This was not the end of the story, not the experiment itself but the conclusions where discussed just after this paper was published. In the same journal a comment was published 4criticizing these conclusions.]
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