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A Receptor-Based Explanation for Tsetse Fly Catch Distribution between Coloured Cloth Panels and Flanking Nets.

Santer RD - PLoS Negl Trop Dis (2015)

Bottom Line: I found that the proportion of tsetse caught on the cloth panel increased with an index representing the chromatic mechanism driving attraction, as would be expected if the same mechanism underlay both long- and close-range attraction.This R7p-driven effect resembles the fly open-space response which is believed to underlie their dispersal towards areas of open sky.As such, the proportion of tsetse that contact a cloth panel likely reflects a combination of deliberate landings by potentially host-seeking tsetse, and accidental collisions by those seeking to disperse, with a separate visual mechanism underlying each behaviour.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental, and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion, United Kingdom.

ABSTRACT
Tsetse flies transmit trypanosomes that cause nagana in cattle, and sleeping sickness in humans. Therefore, optimising visual baits to control tsetse is an important priority. Tsetse are intercepted at visual baits due to their initial attraction to the bait, and their subsequent contact with it due to landing or accidental collision. Attraction is proposed to be driven in part by a chromatic mechanism to which a UV-blue photoreceptor contributes positively, and a UV and a green photoreceptor contribute negatively. Landing responses are elicited by stimuli with low luminance, but many studies also find apparently strong landing responses when stimuli have high UV reflectivity, which would imply that UV wavelengths contribute negatively to attraction at a distance, but positively to landing responses at close range. The strength of landing responses is often judged using the number of tsetse sampled at a cloth panel expressed as a proportion of the combined catch of the cloth panel and a flanking net that samples circling flies. I modelled these data from two previously published field studies, using calculated fly photoreceptor excitations as predictors. I found that the proportion of tsetse caught on the cloth panel increased with an index representing the chromatic mechanism driving attraction, as would be expected if the same mechanism underlay both long- and close-range attraction. However, the proportion of tsetse caught on the cloth panel also increased with excitation of the UV-sensitive R7p photoreceptor, in an apparently separate but interacting behavioural mechanism. This R7p-driven effect resembles the fly open-space response which is believed to underlie their dispersal towards areas of open sky. As such, the proportion of tsetse that contact a cloth panel likely reflects a combination of deliberate landings by potentially host-seeking tsetse, and accidental collisions by those seeking to disperse, with a separate visual mechanism underlying each behaviour.

No MeSH data available.


Related in: MedlinePlus

Pcloth plotted as a function of opponent index describing attraction, and an interacting photoreceptor R7p-driven mechanism.Pcloth values are those from Fig 3, plotted separately for male and female G. f. fuscipes (A and B), and for male and female G. p. palpalis (C and D). The overall trend across datasets was for an increase in Pcloth with increases in the opponent index that explains overall attraction; and an increase in Pcloth with increases in the strength of the photoreceptor R7p response. Plotted grids represent the regression planes statistically tested in Tables 2 and 3, and are the detransformed logits obtained from those linear relationships.
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pntd.0004121.g004: Pcloth plotted as a function of opponent index describing attraction, and an interacting photoreceptor R7p-driven mechanism.Pcloth values are those from Fig 3, plotted separately for male and female G. f. fuscipes (A and B), and for male and female G. p. palpalis (C and D). The overall trend across datasets was for an increase in Pcloth with increases in the opponent index that explains overall attraction; and an increase in Pcloth with increases in the strength of the photoreceptor R7p response. Plotted grids represent the regression planes statistically tested in Tables 2 and 3, and are the detransformed logits obtained from those linear relationships.

Mentions: I next conducted GEE analyses to model Pcloth based upon the opponent index describing visual attraction, excitation values of photoreceptors that may drive a second behavioural mechanism, and the interaction between these two mechanisms (Tables 2 and 3). With the exception of the model containing photoreceptor R8p excitation for the female G. f. fuscipes dataset, all of these models resulted in reductions in QIC and QICC over the linear relationships with opponent index alone presented in table 1. Of these models, that which used the shorter wavelength UV photoreceptor R7p’s response consistently fitted each dataset better than models using excitation values for any other photoreceptor type, and in the R7p models the effects of all predictors were significant (Tables 2 and 3; Fig 4). Judged by differences in QIC >2, no other model was deemed competitive with the R7p model, although for the G. p. palpalis dataset QICC differences <2 provided some support for the alternative models other than that using R8p excitation. Removing the interaction term from any R7p model reduced its fit to the data. Elaborating any R7p model with an additional photoreceptor excitation value and its interaction term also reduced its fit to the data (S1 and S2 tables).


A Receptor-Based Explanation for Tsetse Fly Catch Distribution between Coloured Cloth Panels and Flanking Nets.

Santer RD - PLoS Negl Trop Dis (2015)

Pcloth plotted as a function of opponent index describing attraction, and an interacting photoreceptor R7p-driven mechanism.Pcloth values are those from Fig 3, plotted separately for male and female G. f. fuscipes (A and B), and for male and female G. p. palpalis (C and D). The overall trend across datasets was for an increase in Pcloth with increases in the opponent index that explains overall attraction; and an increase in Pcloth with increases in the strength of the photoreceptor R7p response. Plotted grids represent the regression planes statistically tested in Tables 2 and 3, and are the detransformed logits obtained from those linear relationships.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608566&req=5

pntd.0004121.g004: Pcloth plotted as a function of opponent index describing attraction, and an interacting photoreceptor R7p-driven mechanism.Pcloth values are those from Fig 3, plotted separately for male and female G. f. fuscipes (A and B), and for male and female G. p. palpalis (C and D). The overall trend across datasets was for an increase in Pcloth with increases in the opponent index that explains overall attraction; and an increase in Pcloth with increases in the strength of the photoreceptor R7p response. Plotted grids represent the regression planes statistically tested in Tables 2 and 3, and are the detransformed logits obtained from those linear relationships.
Mentions: I next conducted GEE analyses to model Pcloth based upon the opponent index describing visual attraction, excitation values of photoreceptors that may drive a second behavioural mechanism, and the interaction between these two mechanisms (Tables 2 and 3). With the exception of the model containing photoreceptor R8p excitation for the female G. f. fuscipes dataset, all of these models resulted in reductions in QIC and QICC over the linear relationships with opponent index alone presented in table 1. Of these models, that which used the shorter wavelength UV photoreceptor R7p’s response consistently fitted each dataset better than models using excitation values for any other photoreceptor type, and in the R7p models the effects of all predictors were significant (Tables 2 and 3; Fig 4). Judged by differences in QIC >2, no other model was deemed competitive with the R7p model, although for the G. p. palpalis dataset QICC differences <2 provided some support for the alternative models other than that using R8p excitation. Removing the interaction term from any R7p model reduced its fit to the data. Elaborating any R7p model with an additional photoreceptor excitation value and its interaction term also reduced its fit to the data (S1 and S2 tables).

Bottom Line: I found that the proportion of tsetse caught on the cloth panel increased with an index representing the chromatic mechanism driving attraction, as would be expected if the same mechanism underlay both long- and close-range attraction.This R7p-driven effect resembles the fly open-space response which is believed to underlie their dispersal towards areas of open sky.As such, the proportion of tsetse that contact a cloth panel likely reflects a combination of deliberate landings by potentially host-seeking tsetse, and accidental collisions by those seeking to disperse, with a separate visual mechanism underlying each behaviour.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental, and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion, United Kingdom.

ABSTRACT
Tsetse flies transmit trypanosomes that cause nagana in cattle, and sleeping sickness in humans. Therefore, optimising visual baits to control tsetse is an important priority. Tsetse are intercepted at visual baits due to their initial attraction to the bait, and their subsequent contact with it due to landing or accidental collision. Attraction is proposed to be driven in part by a chromatic mechanism to which a UV-blue photoreceptor contributes positively, and a UV and a green photoreceptor contribute negatively. Landing responses are elicited by stimuli with low luminance, but many studies also find apparently strong landing responses when stimuli have high UV reflectivity, which would imply that UV wavelengths contribute negatively to attraction at a distance, but positively to landing responses at close range. The strength of landing responses is often judged using the number of tsetse sampled at a cloth panel expressed as a proportion of the combined catch of the cloth panel and a flanking net that samples circling flies. I modelled these data from two previously published field studies, using calculated fly photoreceptor excitations as predictors. I found that the proportion of tsetse caught on the cloth panel increased with an index representing the chromatic mechanism driving attraction, as would be expected if the same mechanism underlay both long- and close-range attraction. However, the proportion of tsetse caught on the cloth panel also increased with excitation of the UV-sensitive R7p photoreceptor, in an apparently separate but interacting behavioural mechanism. This R7p-driven effect resembles the fly open-space response which is believed to underlie their dispersal towards areas of open sky. As such, the proportion of tsetse that contact a cloth panel likely reflects a combination of deliberate landings by potentially host-seeking tsetse, and accidental collisions by those seeking to disperse, with a separate visual mechanism underlying each behaviour.

No MeSH data available.


Related in: MedlinePlus