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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 was non-linearly related to an opponent index describing the mechanism of visual attraction.Pcloth values are plotted for male (filled circles) and female (open circles) G. f. fuscipes (A) and G. p. palpalis (B). Data for G. f. fuscipes come from a field study in which e-cloths and e-nets were both 0.25 m x 0.25 m [9], and those for G. p. palpalis from a field study in which e-cloths were 1.0 m x 1.0 m, and flanking e-nets 0.5 m x 1.0 m [8]. The x-axes of both plots display a calculated photoreceptor opponent index that approximates the previously reported mechanism of tsetse attraction to approach a visual bait, and with which combined catches of e-cloth and e-net were positively related in both field studies (this trend is illustrated by the horizontal arrow below panel B) [10]. The plotted relationships are detransformed logits obtained from the statistical analyses in Table 1. Vertical green lines indicate an opponent index calculated for the assumed background of green leaves.
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pntd.0004121.g003: Pcloth was non-linearly related to an opponent index describing the mechanism of visual attraction.Pcloth values are plotted for male (filled circles) and female (open circles) G. f. fuscipes (A) and G. p. palpalis (B). Data for G. f. fuscipes come from a field study in which e-cloths and e-nets were both 0.25 m x 0.25 m [9], and those for G. p. palpalis from a field study in which e-cloths were 1.0 m x 1.0 m, and flanking e-nets 0.5 m x 1.0 m [8]. The x-axes of both plots display a calculated photoreceptor opponent index that approximates the previously reported mechanism of tsetse attraction to approach a visual bait, and with which combined catches of e-cloth and e-net were positively related in both field studies (this trend is illustrated by the horizontal arrow below panel B) [10]. The plotted relationships are detransformed logits obtained from the statistical analyses in Table 1. Vertical green lines indicate an opponent index calculated for the assumed background of green leaves.

Mentions: The chromatic mechanism proposed to underlie tsetse attraction can be approximated by a simple opponent index, and the combined catch of an e-cloth and flanking e-net was previously shown to have a positive relationship with this index (see Fig 7 of [10]). Fig 3 shows the relationship between this same opponent index and Pcloth (the proportion of the combined catch that was caught on the e-cloth), which represents the propensity of tsetse to directly contact the cloth panel in preference to first, or only, circling around it (see Fig 2). In contrast to combined catches, Pcloth did not have a simple, positive relationship with opponent index. GEE models containing a quadratic term had lower QIC and QICC versus simpler linear models for all datasets (Table 1; Fig 3). However, whilst the fit of the quadratic model was substantially better than that of the linear model for G. f. fuscipes, the two models were competitive for G. p. palpalis (for which the linear model described a negative relationship between Pcloth and opponent index).


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

Santer RD - PLoS Negl Trop Dis (2015)

Pcloth was non-linearly related to an opponent index describing the mechanism of visual attraction.Pcloth values are plotted for male (filled circles) and female (open circles) G. f. fuscipes (A) and G. p. palpalis (B). Data for G. f. fuscipes come from a field study in which e-cloths and e-nets were both 0.25 m x 0.25 m [9], and those for G. p. palpalis from a field study in which e-cloths were 1.0 m x 1.0 m, and flanking e-nets 0.5 m x 1.0 m [8]. The x-axes of both plots display a calculated photoreceptor opponent index that approximates the previously reported mechanism of tsetse attraction to approach a visual bait, and with which combined catches of e-cloth and e-net were positively related in both field studies (this trend is illustrated by the horizontal arrow below panel B) [10]. The plotted relationships are detransformed logits obtained from the statistical analyses in Table 1. Vertical green lines indicate an opponent index calculated for the assumed background of green leaves.
© Copyright Policy
Related In: Results  -  Collection

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

pntd.0004121.g003: Pcloth was non-linearly related to an opponent index describing the mechanism of visual attraction.Pcloth values are plotted for male (filled circles) and female (open circles) G. f. fuscipes (A) and G. p. palpalis (B). Data for G. f. fuscipes come from a field study in which e-cloths and e-nets were both 0.25 m x 0.25 m [9], and those for G. p. palpalis from a field study in which e-cloths were 1.0 m x 1.0 m, and flanking e-nets 0.5 m x 1.0 m [8]. The x-axes of both plots display a calculated photoreceptor opponent index that approximates the previously reported mechanism of tsetse attraction to approach a visual bait, and with which combined catches of e-cloth and e-net were positively related in both field studies (this trend is illustrated by the horizontal arrow below panel B) [10]. The plotted relationships are detransformed logits obtained from the statistical analyses in Table 1. Vertical green lines indicate an opponent index calculated for the assumed background of green leaves.
Mentions: The chromatic mechanism proposed to underlie tsetse attraction can be approximated by a simple opponent index, and the combined catch of an e-cloth and flanking e-net was previously shown to have a positive relationship with this index (see Fig 7 of [10]). Fig 3 shows the relationship between this same opponent index and Pcloth (the proportion of the combined catch that was caught on the e-cloth), which represents the propensity of tsetse to directly contact the cloth panel in preference to first, or only, circling around it (see Fig 2). In contrast to combined catches, Pcloth did not have a simple, positive relationship with opponent index. GEE models containing a quadratic term had lower QIC and QICC versus simpler linear models for all datasets (Table 1; Fig 3). However, whilst the fit of the quadratic model was substantially better than that of the linear model for G. f. fuscipes, the two models were competitive for G. p. palpalis (for which the linear model described a negative relationship between Pcloth and opponent index).

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