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Effects of Floral Scents and Their Dietary Experiences on the Feeding Preference in the Blowfly, Phormia regina.

Maeda T, Tamotsu M, Yamaoka R, Ozaki M - Front Integr Neurosci (2015)

Bottom Line: After feeding on sucrose solutions flavored with floral scents for 5 days, the scents did not consistently show the previously observed effects.The results suggested that olfactory inputs through these organs play different roles in forming or modifying feeding preferences.Thus, our study contributes to an understanding of underlying mechanisms associated with the convergent processing of olfactory inputs with taste information, which affects feeding preference or appetite.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Graduate School of Science, Kobe University Kobe, Japan.

ABSTRACT
The flowers of different plant species have diverse scents with varied chemical compositions. Hence, every floral scent does not uniformly affect insect feeding preferences. The blowfly, Phormia regina, is a nectar feeder, and when a fly feeds on flower nectar, its olfactory organs, antennae, and maxillary palps are exposed to the scent. Generally, feeding preference is influenced by food flavor, which relies on both taste and odor. Therefore, the flies perceive the sweet taste of nectar and the particular scent of the flower simultaneously, and this olfactory information affects their feeding preference. Here, we show that the floral scents of 50 plant species have various effects on their sucrose feeding motivation, which was evaluated using the proboscis extension reflex (PER). Those floral scents were first categorized into three groups, based on their effects on the PER threshold sucrose concentration, which indicates whether a fly innately dislikes, ignores, or likes the target scent. Moreover, memory of olfactory experience with those floral scents during sugar feeding influenced the PER threshold. After feeding on sucrose solutions flavored with floral scents for 5 days, the scents did not consistently show the previously observed effects. Considering such empirical effects of scents on the PER threshold, we categorized the effects of the 50 tested floral scents on feeding preference into 16 of all possible 27 theoretical types. We then conducted the same experiments with flies whose antennae or maxillary palps were ablated prior to PER test in a fly group naïve to floral scents and prior to the olfactory experience during sugar feeding in the other fly group in order to test how these organs were involved in the effect of the floral scent. The results suggested that olfactory inputs through these organs play different roles in forming or modifying feeding preferences. Thus, our study contributes to an understanding of underlying mechanisms associated with the convergent processing of olfactory inputs with taste information, which affects feeding preference or appetite.

No MeSH data available.


Related in: MedlinePlus

Theoretical types of fly appetite change. (A–C) Three possible effects of floral scents on the sucrose concentration-PER curves in non-experienced flies. (a–i) Nine possible effects of floral scents on the sucrose concentration-PER curves in experienced flies. The sucrose concentration-PER curves in the absence (black closed circles) and presence (red closed circles) of a scent are drawn. The black and red closed arrowheads indicate the mean PER threshold of sucrose concentrations in the absence and presence of scents, respectively. The concentration-PER curves in the absence of scent in non-experienced flies are drawn with open circles, and the mean PER concentration is indicated by open arrowheads. For examples, the PER curves are drawn, so that the mean threshold is increased from 0.1 to 0.5 M or decreased to 0.02 M according to respective appetite change.
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Figure 1: Theoretical types of fly appetite change. (A–C) Three possible effects of floral scents on the sucrose concentration-PER curves in non-experienced flies. (a–i) Nine possible effects of floral scents on the sucrose concentration-PER curves in experienced flies. The sucrose concentration-PER curves in the absence (black closed circles) and presence (red closed circles) of a scent are drawn. The black and red closed arrowheads indicate the mean PER threshold of sucrose concentrations in the absence and presence of scents, respectively. The concentration-PER curves in the absence of scent in non-experienced flies are drawn with open circles, and the mean PER concentration is indicated by open arrowheads. For examples, the PER curves are drawn, so that the mean threshold is increased from 0.1 to 0.5 M or decreased to 0.02 M according to respective appetite change.

Mentions: In the present study, the term “appetite” was used to indicate the motivation for feeding, which we evaluated using the PER threshold as a necessary prerequisite to feeding. Decreased and increased appetites in flies indicated high and low PER thresholds to sucrose, respectively. For the PER test, we obtained the thresholds in individual test flies of 8-days-old and compared them between populations and conditions. Prior to the PER test, 20 individuals including both sexes were randomly chosen from each group and starved for 24–36 h, being provided by water, and were immobilized by securing the wings with aluminum clothespins. Before the PER test, flies were provided with water to satiation. Stimulus solutions for the PER test included 11 steps of sucrose concentrations (prepared by two-fold serial dilutions with distilled water) or five steps (prepared by four-fold serial dilutions with distilled water), and both preparations started at a 1 M-sucrose concentration. The labellar contact chemosensilla of flies were carefully stimulated by hand with each sucrose concentration in a wide-mouth 200 mL pipette tip, beginning with the lowest concentration, so that flies would not ingest stimulus solutions. If necessary, this stimulation step was conducted under a stereomicroscope (SZX-9, Olympus, Tokyo, Japan). We then examined the effects of the presence of floral scents, and the PER test was performed with the odor source set approximately 2 cm away from the fly. The sucrose concentration to which the fly first fully extended its proboscis was defined as the PER threshold at the individual level. Thus, the classification (see Figure 1) was determined so that the statistically examined differences in individual PER thresholds defined all concentration-PER curve shifts (p > 0.05 for non-significant shifts or p < 0.05 for significant shifts, Mann-Whitney U test; n = 20). The PER value for each fly was plotted against the sucrose concentration, and the mean threshold was determined as half the maximum sucrose concentration that induced PER in 50% of the test flies. The statistical test for the mean threshold (Mann-Whitney U test) was not done except for the data of Figure 5I, which was obtained from five sets of PER tests using 20 flies each. When the sucrose concentration-PER curve shifted to the left in the presence of a scent and the mean PER threshold decreased, the fly appetite was increased by the scent and vice versa. We examined each floral scent twice during two seasonal rounds in different years, and we reported the results of 50 floral scents and their effects on appetite, which were qualitatively classified into the same types.


Effects of Floral Scents and Their Dietary Experiences on the Feeding Preference in the Blowfly, Phormia regina.

Maeda T, Tamotsu M, Yamaoka R, Ozaki M - Front Integr Neurosci (2015)

Theoretical types of fly appetite change. (A–C) Three possible effects of floral scents on the sucrose concentration-PER curves in non-experienced flies. (a–i) Nine possible effects of floral scents on the sucrose concentration-PER curves in experienced flies. The sucrose concentration-PER curves in the absence (black closed circles) and presence (red closed circles) of a scent are drawn. The black and red closed arrowheads indicate the mean PER threshold of sucrose concentrations in the absence and presence of scents, respectively. The concentration-PER curves in the absence of scent in non-experienced flies are drawn with open circles, and the mean PER concentration is indicated by open arrowheads. For examples, the PER curves are drawn, so that the mean threshold is increased from 0.1 to 0.5 M or decreased to 0.02 M according to respective appetite change.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664696&req=5

Figure 1: Theoretical types of fly appetite change. (A–C) Three possible effects of floral scents on the sucrose concentration-PER curves in non-experienced flies. (a–i) Nine possible effects of floral scents on the sucrose concentration-PER curves in experienced flies. The sucrose concentration-PER curves in the absence (black closed circles) and presence (red closed circles) of a scent are drawn. The black and red closed arrowheads indicate the mean PER threshold of sucrose concentrations in the absence and presence of scents, respectively. The concentration-PER curves in the absence of scent in non-experienced flies are drawn with open circles, and the mean PER concentration is indicated by open arrowheads. For examples, the PER curves are drawn, so that the mean threshold is increased from 0.1 to 0.5 M or decreased to 0.02 M according to respective appetite change.
Mentions: In the present study, the term “appetite” was used to indicate the motivation for feeding, which we evaluated using the PER threshold as a necessary prerequisite to feeding. Decreased and increased appetites in flies indicated high and low PER thresholds to sucrose, respectively. For the PER test, we obtained the thresholds in individual test flies of 8-days-old and compared them between populations and conditions. Prior to the PER test, 20 individuals including both sexes were randomly chosen from each group and starved for 24–36 h, being provided by water, and were immobilized by securing the wings with aluminum clothespins. Before the PER test, flies were provided with water to satiation. Stimulus solutions for the PER test included 11 steps of sucrose concentrations (prepared by two-fold serial dilutions with distilled water) or five steps (prepared by four-fold serial dilutions with distilled water), and both preparations started at a 1 M-sucrose concentration. The labellar contact chemosensilla of flies were carefully stimulated by hand with each sucrose concentration in a wide-mouth 200 mL pipette tip, beginning with the lowest concentration, so that flies would not ingest stimulus solutions. If necessary, this stimulation step was conducted under a stereomicroscope (SZX-9, Olympus, Tokyo, Japan). We then examined the effects of the presence of floral scents, and the PER test was performed with the odor source set approximately 2 cm away from the fly. The sucrose concentration to which the fly first fully extended its proboscis was defined as the PER threshold at the individual level. Thus, the classification (see Figure 1) was determined so that the statistically examined differences in individual PER thresholds defined all concentration-PER curve shifts (p > 0.05 for non-significant shifts or p < 0.05 for significant shifts, Mann-Whitney U test; n = 20). The PER value for each fly was plotted against the sucrose concentration, and the mean threshold was determined as half the maximum sucrose concentration that induced PER in 50% of the test flies. The statistical test for the mean threshold (Mann-Whitney U test) was not done except for the data of Figure 5I, which was obtained from five sets of PER tests using 20 flies each. When the sucrose concentration-PER curve shifted to the left in the presence of a scent and the mean PER threshold decreased, the fly appetite was increased by the scent and vice versa. We examined each floral scent twice during two seasonal rounds in different years, and we reported the results of 50 floral scents and their effects on appetite, which were qualitatively classified into the same types.

Bottom Line: After feeding on sucrose solutions flavored with floral scents for 5 days, the scents did not consistently show the previously observed effects.The results suggested that olfactory inputs through these organs play different roles in forming or modifying feeding preferences.Thus, our study contributes to an understanding of underlying mechanisms associated with the convergent processing of olfactory inputs with taste information, which affects feeding preference or appetite.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Graduate School of Science, Kobe University Kobe, Japan.

ABSTRACT
The flowers of different plant species have diverse scents with varied chemical compositions. Hence, every floral scent does not uniformly affect insect feeding preferences. The blowfly, Phormia regina, is a nectar feeder, and when a fly feeds on flower nectar, its olfactory organs, antennae, and maxillary palps are exposed to the scent. Generally, feeding preference is influenced by food flavor, which relies on both taste and odor. Therefore, the flies perceive the sweet taste of nectar and the particular scent of the flower simultaneously, and this olfactory information affects their feeding preference. Here, we show that the floral scents of 50 plant species have various effects on their sucrose feeding motivation, which was evaluated using the proboscis extension reflex (PER). Those floral scents were first categorized into three groups, based on their effects on the PER threshold sucrose concentration, which indicates whether a fly innately dislikes, ignores, or likes the target scent. Moreover, memory of olfactory experience with those floral scents during sugar feeding influenced the PER threshold. After feeding on sucrose solutions flavored with floral scents for 5 days, the scents did not consistently show the previously observed effects. Considering such empirical effects of scents on the PER threshold, we categorized the effects of the 50 tested floral scents on feeding preference into 16 of all possible 27 theoretical types. We then conducted the same experiments with flies whose antennae or maxillary palps were ablated prior to PER test in a fly group naïve to floral scents and prior to the olfactory experience during sugar feeding in the other fly group in order to test how these organs were involved in the effect of the floral scent. The results suggested that olfactory inputs through these organs play different roles in forming or modifying feeding preferences. Thus, our study contributes to an understanding of underlying mechanisms associated with the convergent processing of olfactory inputs with taste information, which affects feeding preference or appetite.

No MeSH data available.


Related in: MedlinePlus