Concentration and Membrane Fluidity Dependence of Odor Discrimination in the Turtle Olfactory System

Abstract

In the present study, we examined the concentration dependence of odor discrimination in turtle olfactory bulbar responses using the cross-adaptation technique. In the odorant pairs with diverse molecular structures, the degree of discrimination was unchanged or only slightly decreased with an increase in odorant concentrations, suggesting that odorants are well discriminated even at high concentrations. In the odorant pairs with closely related molecular structures, the degree of discrimination was decreased with an increase in odorant concentrations. An increase in the temperature of turtle olfactory epithelium also decreased the ability to discriminate these odorants. There was a good correlation between changes in the odor discriminating ability induced by an increase in odor concentrations and those induced by a temperature increase. The liposomes were made of lipids extracted from the turtle olfactory epithelia and changes of their membrane fluidity induced by adsorption of odorants were monitored with DPH. There was a good correlation between a decrease in odor discriminating ability and the membrane fluidity changes induced by odorants. We suggest that decreases in odor discriminating ability induced either by an increase in odor concentration or by a temperature increase are ultimately caused by changes in the membrane fluidity.

Temperature-dependent changes in the host-seeking behaviors of parasitic nematodes

“…For example, Oriental fruit moths show a decreased ability to discriminate among pheromone blends at higher temperatures [ 58 ], and aged Caenorhabditis elegans adults show decreased attraction to benzaldehyde [ 59 ]. Temperature also modulates olfactory discrimination in turtles [ 60 , 61 ], olfactory sensitivity in the fruit fly Drosophila melanogaster [ 62 , 63 ] , and CO 2 sensitivity in C. elegans adults [ 64 ]. However, the robust, long-lasting temperature-induced olfactory valence changes that occur in parasitic nematodes have not been previously reported.…”

Environmental temperature modulates olfactory reception in Drosophila melanogaster

“…Environmental temperature affects two processes: the concentration of volatiles in the air and the internal physiology of the animal. In poikilothermic animals, body temperature, membrane fluidity (Wodtke, 1981;Kashiwayanagi et al, 1997;Ohtsu et al, 1998;Overgaard et al, 2005) and metabolic rate (Gillooly et al, 2001;Clarke, 2006) are particularly affected. In our experiments, we tried to clarify if active mechanisms also participate in the olfactory acclimation to temperatures within the normal range for D. melanogaster that was seen at the behavioral level in response to general odors (Riveron et al, 2009).…”

“…Although there are some studies addressing the influence of temperature in the olfactory discrimination of general odors in turtles (Hanada et al, 1994;Kashiwayanagi et al, 1997), little is known about the temperature-dependent modulation of the response to these odorants in insects. Recent behavioral studies in D. melanogaster reported biological acclimation to temperature as to compensate for the change of odorant concentration induced by temperature shifts (Riveron et al, 2009).…”

Odor Discrimination by Lipid Membranes

“…It has been shown that lipid monolayers from bovine epithelium have a change in surface tension that is linearly correlated to odorant threshold concentration [ 36 ]. Furthermore, it has been shown that olfaction can be temperature-sensitive [ 39 , 40 ]. Further experiments showed a strong correlation with the odorant’s effect on membrane fluidity [ 39 ].…”

“…Furthermore, it has been shown that olfaction can be temperature-sensitive [ 39 , 40 ]. Further experiments showed a strong correlation with the odorant’s effect on membrane fluidity [ 39 ].…”