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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

Measurement and interpretation of tsetse catch distribution between e-cloths and flanking e-nets.Arrows provide a schematic illustration of tsetse flight paths. (a) Tsetse attracted into the vicinity of an e-cloth may sometimes fly directly towards it and make contact. (b) More often, tsetse do not approach the e-cloth directly, but instead circle in its vicinity or alight nearby. Some of these flies make accidental contact with the e-net because it is difficult for them to detect. The tsetse catch of the e-cloth plus that of the e-net is known as the combined catch and is taken to indicate overall attraction to approach the visual bait. The proportion of the combined catch that was intercepted at the e-cloth is termed Pcloth in this study. This measurement indicates the prevalence of direct contact with the e-cloth over circling behaviour. For this reason, this measurement is often referred to as the ‘landing score’.
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pntd.0004121.g002: Measurement and interpretation of tsetse catch distribution between e-cloths and flanking e-nets.Arrows provide a schematic illustration of tsetse flight paths. (a) Tsetse attracted into the vicinity of an e-cloth may sometimes fly directly towards it and make contact. (b) More often, tsetse do not approach the e-cloth directly, but instead circle in its vicinity or alight nearby. Some of these flies make accidental contact with the e-net because it is difficult for them to detect. The tsetse catch of the e-cloth plus that of the e-net is known as the combined catch and is taken to indicate overall attraction to approach the visual bait. The proportion of the combined catch that was intercepted at the e-cloth is termed Pcloth in this study. This measurement indicates the prevalence of direct contact with the e-cloth over circling behaviour. For this reason, this measurement is often referred to as the ‘landing score’.

Mentions: Videographic observations demonstrate that when tsetse alight on a black cloth target, they very rarely do so after having made a direct approach to it. Instead, the initial approach is followed by local circling or alighting on the ground before the fly eventually lands on the target [13]. This accords with data gained using combinations of e-cloth and flanking e-net, where the e-net sample of circling flies often exceeds the e-cloth sample of those that land directly [5,6,9]. Furthermore, intricate studies using e-nets reveal that only some of the flies attracted to a bait ultimately land at all, the others departing after having circled it [14,15]. Since the insecticide-treated cloth panels used for tsetse control can only be effective if tsetse make contact with them, insecticide-treated flanking nets are advocated to intercept and kill circling flies by inducing accidental collisions [5,6,21]. However, the cues that induce tsetse to alight remain an interesting and little understood area of investigation. Where field studies have employed combinations of e-cloth and flanking e-net, the catch of the e-cloth expressed as a proportion of the combined catch of the e-cloth and e-net (henceforth, Pcloth) is used to provide a measurement of tsetse preference for direct landing over circling (see Fig 2). As such, this measurement is commonly referred to as the ‘landing score’. Pcloth is positively influenced by a bait’s reflectance of UV wavelengths, or low overall luminance, and the former observation has lead to the assertion that UV wavelengths are important cues for eliciting landing [8,15,22,23] (but see also [9]). Hence, a number of studies have investigated dual-colour baits, incorporating panels of colour that strongly stimulate tsetse to approach, and others that provide the putative landing cues (e.g. [22,24]).


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

Santer RD - PLoS Negl Trop Dis (2015)

Measurement and interpretation of tsetse catch distribution between e-cloths and flanking e-nets.Arrows provide a schematic illustration of tsetse flight paths. (a) Tsetse attracted into the vicinity of an e-cloth may sometimes fly directly towards it and make contact. (b) More often, tsetse do not approach the e-cloth directly, but instead circle in its vicinity or alight nearby. Some of these flies make accidental contact with the e-net because it is difficult for them to detect. The tsetse catch of the e-cloth plus that of the e-net is known as the combined catch and is taken to indicate overall attraction to approach the visual bait. The proportion of the combined catch that was intercepted at the e-cloth is termed Pcloth in this study. This measurement indicates the prevalence of direct contact with the e-cloth over circling behaviour. For this reason, this measurement is often referred to as the ‘landing score’.
© Copyright Policy
Related In: Results  -  Collection

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

pntd.0004121.g002: Measurement and interpretation of tsetse catch distribution between e-cloths and flanking e-nets.Arrows provide a schematic illustration of tsetse flight paths. (a) Tsetse attracted into the vicinity of an e-cloth may sometimes fly directly towards it and make contact. (b) More often, tsetse do not approach the e-cloth directly, but instead circle in its vicinity or alight nearby. Some of these flies make accidental contact with the e-net because it is difficult for them to detect. The tsetse catch of the e-cloth plus that of the e-net is known as the combined catch and is taken to indicate overall attraction to approach the visual bait. The proportion of the combined catch that was intercepted at the e-cloth is termed Pcloth in this study. This measurement indicates the prevalence of direct contact with the e-cloth over circling behaviour. For this reason, this measurement is often referred to as the ‘landing score’.
Mentions: Videographic observations demonstrate that when tsetse alight on a black cloth target, they very rarely do so after having made a direct approach to it. Instead, the initial approach is followed by local circling or alighting on the ground before the fly eventually lands on the target [13]. This accords with data gained using combinations of e-cloth and flanking e-net, where the e-net sample of circling flies often exceeds the e-cloth sample of those that land directly [5,6,9]. Furthermore, intricate studies using e-nets reveal that only some of the flies attracted to a bait ultimately land at all, the others departing after having circled it [14,15]. Since the insecticide-treated cloth panels used for tsetse control can only be effective if tsetse make contact with them, insecticide-treated flanking nets are advocated to intercept and kill circling flies by inducing accidental collisions [5,6,21]. However, the cues that induce tsetse to alight remain an interesting and little understood area of investigation. Where field studies have employed combinations of e-cloth and flanking e-net, the catch of the e-cloth expressed as a proportion of the combined catch of the e-cloth and e-net (henceforth, Pcloth) is used to provide a measurement of tsetse preference for direct landing over circling (see Fig 2). As such, this measurement is commonly referred to as the ‘landing score’. Pcloth is positively influenced by a bait’s reflectance of UV wavelengths, or low overall luminance, and the former observation has lead to the assertion that UV wavelengths are important cues for eliciting landing [8,15,22,23] (but see also [9]). Hence, a number of studies have investigated dual-colour baits, incorporating panels of colour that strongly stimulate tsetse to approach, and others that provide the putative landing cues (e.g. [22,24]).

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