Valve driver ii

Scale bars: 1 cm in B,C. To visualize the odor plume produced by these delivery systems, we generated a smoke plume by pumping mineral oil through a hypodermic needle,across which we placed a high voltage that burned the oil.

The smoke thus generated was then injected into the tunnel under the same conditions as in the odor plume experiments and the plume's trajectory and dimensions were measured. The ribbon plume was slightly sinuous, with a mean instantaneous diameter of 0. The envelope described by the undulating plume, along this same length, was 1. We similarly measured the mean instantaneous diameter of the large diameter plume as 4. The position of the plume within the tunnel was determined by recording its position at its upwind entrance and at the downwind exit and linearly interpolating between the two.

Homogeneous odor cloud experiments used the same banana odor, but in this case, air was pumped into ml of the filtrate at A large cardboard box, 76 cm square, was inserted into the tunnel inlet and served as a mixing chamber for the odor. Four computer fans were positioned approximately equidistant from each other and from the walls of the cardboard box Fig.

Four PVC tubes carried the odor from the vial to the cardboard box where the odor was released immediately upstream of the four small fans and was mixed thoroughly in the mixing chamber as judged by experiments with smoke tracers.

By the time it reached the working section, however, the smoke plume was too diffuse to visualize. Animals were deprived of food, but not water,for h prior to experimentation in order to motivate flight. On the day of experimentation, approximately flies were kept in a 50 ml vial beneath the tunnel where they acclimated for 10 min to 2 h, depending on when they were introduced into the tunnel, as described below, with an experiment lasting approximately 2 h.

This vial was connected, via a stop cock,to an acrylic tube of diameter 5 mm that penetrated the floor of the tunnel at a distance This tube was capped by a pipette tip such that flies emerging from the tube were positioned halfway between the tunnel walls and at approximately half the height of the tunnel.

Flies were introduced into the tunnel individually such that the odor plume intercepted the fly release tube at approximately the height of the emerging flies, immediately exposing them to the odor.

If a fly did not take flight shortly after emerging into the tunnel, one or more flies were introduced in order to increase the probability that one would do so.

Flies were captured by the imaging system from take-off at the release tube or shortly after take-off. Individual trajectories were often recorded as several trajectory fragments due to loss of the fly by the visualization system. As such, a single mean value based on all trajectory fragments was calculated for each trajectory parameter for each fly, except as noted below.

In all experiments, flies were recorded until they landed. The flies were vacuumed out of the tunnel approximately every 10 min. The tunnel was illuminated by a linear array of 10 halogen bulbs on each side yielding a luminance of lux within the working section. The 3-dimensional 3-D flight trajectories were sampled at 60 frames s -1 and reconstructed with commercially available software, Trackit 3-D Fry et al.

In the pulsed plume experiments, the state of the solenoid valve was recorded at every time point together with the 3-D fly position. We were thus able to determine the location of all pulses in the tunnel at any given time as well as the fly's position relative to them. This allowed us to determine the moment of plume entry and plume loss.

The fly trajectories were smoothed to remove digitization errors by low-pass filtering with a fifth order Butterworth filter using a frequency cut-off of 7. All analyses of fly trajectories made use of software written using Matlab Mathworks. Only trajectories longer than 0. Flies approaching the odor source generally slowed down and ceased to respond with upwind surges, due either to the visual effects of the plume source, changes in plume dynamics, or both.

Because of these qualitative changes in flight trajectories as the animals approached and landed on the odor release site, flight within the most upwind 0. In order to visualize the distribution of flies within the wind tunnel, individual trajectories Fig.

Flight trajectories were described in terms of a number of variables that were calculated at every frame in the flight trajectory Fig. Ground speed was determined from the distance that the animal traveled in the horizontal plane between samples.

Cross-wind velocity and upwind velocity were the components of ground speed directed across the width of the tunnel and up its long axis, respectively. Vertical velocity was determined from the distance that the animal traveled in the vertical plane between samples. Heading track angle was the projection of 3-D heading in the horizontal plane of the fly and is equivalent to the angle between the ground speed vector and the long axis of the tunnel.

Airspeed was calculated trigonometrically using ground speed, wind speed and heading, and is the velocity of the animal in the horizontal plane relative to the wind.

Finally, plume distance was defined as the shortest absolute 3-D distance between the fly and the plume. Substantial variability in the overall shape of flight trajectories, relative to published trajectories for moths, made it difficult to assign meaningful parameters to the counterturning behavior, such as turn frequency or inter-reversal distance.

This value varies between 0 and 1 and is a measure of the dispersion around the mean heading Batschelet, To test for differences in mean direction between experimental conditions,we implemented the non-parametric test for common mean direction suggested by Fisher [ Fisher, , pp.

To test for differences in the angular dispersions of two samples about their respective means, we used the non-parametric test suggested by Batschelet [ Batschelet, ,pp. Non-parametric tests were used due to their limited assumptions about angular distributions, namely that the data need not be fit by von Mises distributions.

In successive iterations, we fit a model containing one additional mode 2VM, etc. The gof of the new model is calculated to obtain U 2 VM. To assess the significance probability of the fit, we generate parametric bootstrap samples of the same size as the original dataset.

All statistical analyses were conducted using custom routines written in Matlab. Transit histograms, viewed from above, of flies released at the downstream end of the tunnel in still air A, flies and in the presence of a 0.

Based on a mixture of von Mises distributions, flight headings were bimodally distributed up E A histogram of the distribution of flies across the tunnel's width indicates that flies manifested a centering response within the central 0. Flight in only the central section was analyzed in order to minimize the visual effects of the odor- and fly-releasing tubes.

While flying in the wind tunnel, D. Furthermore, mean trajectory headings seemed to be directed bimodally along the longitudinal axis of the tunnel in still air Fig. We tested both unimodal and bimodal fits of von Mises distributions to the mean trajectories both in the presence and absence of wind Tables 1 and 2. In both cases, a model containing two modes was a better fit to the data than was a unimodal model.

Comparing those bimodal fits, however, in still air, the mode directed towards Thus, while both samples were better fit by bimodal distributions, the mode representing upwind flight was substantially larger in the presence of wind. Furthermore, non-parametric circular tests indicated no significant differences between the mean headings d. While flying upwind,flies manifested a centering response like the one described in honeybees by Srinivasan and colleagues Fig.

Because this response could have been influenced by visual orientation to the odor and fly releasing tubes, the analysis was restricted to the central 0. Fitting a mixture of von Mises distributions to mean heading vectors of flies in a no odor, no wind environment.

For each model, a goodness of fit was calculated and significance tested against a parametric bootstrap as described in the Materials and methods.

P represents the probability that the data are better fit by a model containing the corresponding number of modes than by a model containing additional modes. Fitting a mixture of von Mises distributions to mean heading vectors of flies in a no odor, plus wind environment.

Details as in Table 1. Flies orient towards a conspicuous visual object, a black post white dot ,in the absence, but not in the presence of wind. Transit histograms, with flies viewed from above, in no wind A, 67 flies and in a 0. The structure of the visual environment, especially the presence of conspicuous, high-contrast objects, influences the odor-mediated flight trajectories of Drosophila Frye et al. We thus tested the relative strength of anemotaxis and target orientation in structuring flight trajectories by placing a black post, 1.

In the presence of a 0. Because of the highly reproducible flow conditions within the wind tunnel,we were able to estimate the location and size of the ribbon odor plume. This position was defined as a 1 cm diameter cylinder surrounding the measured path of a smoke plume that was introduced into the tunnel under identical flow conditions to those used to produce the ribbon odor plume, allowing us to estimate the time and place where the fly's trajectory intersected the odor plume.

When exposed to a ribbon plume of banana odor in a 0. The effects of plume contact on individual trajectories were often dramatic,but because of the variability of these flight responses, it would be misleading to present a single representative trajectory, and so instead,eight examples of plume oriented flight are shown in Fig.

At one extreme, many flies responded to plume contact by progressing almost directly upwind while increasing their air speed e. At the other extreme, some flies generated trajectories consisting of looping counterturns interspersed with periods of upwind progress e.

Between these two extremes, bouts of straight upwind flight often graded into more sinuous upwind flight e. Despite the variability in responses to plume contact,several features were largely consistent such as the rapid shift from cross-wind to upwind flight, coupled with an increase in air speed following plume contact.

A-H Eight examples of odor-mediated upwind flight with air speed encoded by color. The odor of fermented banana was presented to the flies in the form of a ribbon 1 cm diameter plume. Flight trajectories, viewed from above,showed substantial variability following plume contact plume contact indicated by arrow and black dot. Several features are often salient,however, including a shift from cross-wind to upwind flight as well as a fast upwind surge. Upwind progress is often interrupted by looping counterturns and casting flight directed across wind.

Because of the variability in overall trajectory shape, our analyses focused on short term changes in trajectory parameters associated with plume contact. It is readily apparent, by plotting all of the post-contact fragments from each fly, that flies were able to follow the ribbon plume of banana odor to its source Fig. In clean air,flies were much more evenly distributed throughout the tunnel, indicating that plume tracking was not a response to a narrow turbulent flow Fig.

Analyzing pre-contact and post-contact fragments separately illustrates the substantial changes in flight trajectories that followed plume contact Fig. Prior to plume contact, flight was largely directed across wind. Thus, a plot of total counts of instantaneous trajectory headings better illustrates the trimodal distribution of flight direction prior to plume contact, with modes at 0.

Since these instantaneous headings are not independent of each other, they cannot be subjected to significance testing, and thus we calculated the mean pre- and post-contact trajectory headings for each fly based on all episodes of plume contact. A non-parametric test of the dispersion of these means indicates that flight prior to plume contact was significantly more highly dispersed around its mean of Again testing trajectory means, flies increased their upwind velocity pre-contact: 0.

To visualize the short-term effects of odor encounter on trajectory shape,pre-contact and post-contact fragments were translated and aligned at the point of plume contact Fig. Plotted in this way, the shift from cross-wind to upwind flight following plume contact is apparent Fig. Vertical displacement appeared less variable in the presence or absence of the plume suggesting that flies may tend to maintain a relatively constant height in both conditions Fig.

Flies localize a ribbon plume of banana odor. Transit histograms of post-contact flight indicate that flies localized and maintained close proximity to the plume white bar both in the horizontal A and vertical B dimensions episodes of plume contact from flies. Note that the plume did descend slightly along the tunnel's length and that the white bar accurately represents the approximate plume extent.

The immediate effects of plume contact on a variety of trajectory parameters were analyzed by plotting them as the time series averages of the first episode of plume contact recorded from each fly, aligned relative to the moment of plume contact Fig. Although plume contact appears to affect many parameters, the flies exhibit some of the same behaviors in response to the clean air control. An animal flying upwind can only encounter the plume if it flies vertically or cross-wind.

An insect displacing laterally will eventually encounter the walls of the tunnel, eliciting a visually mediated collision avoidance response Tammero and Dickinson, ,which would be likely to orient it upwind, given the anemotactic response shown in Fig.

Thus, to compare odor-mediated orientation and visual responses, we compared the changes in trajectories from the moment of plume contact or its clean air equivalent in flies flying in the presence and absence of odor. While many of the trajectory parameters changed with similar sign in both treatments, the timing of the responses was substantially advanced in the presence of odor.

The upwind surge was coupled with a significant increase in air speed ms after odor contact; not a surprising result if a fly heads more upwind in the absence of a compensatory decrease in ground speed. Indeed, changes in ground speed were not significantly different between the two treatments at either time point,reflecting the similar control exerted over this parameter under both conditions.

Finally, vertical velocity was low prior to and following plume contact both in the presence and absence of odor, with no significant differences between the treatments, indicating stable altitude control. These results suggest that visually mediated responses to wall approach likely contributed to velocity modulation in the ribbon plume of banana odor as well as in the absence of odor. Comparisons of changes in mean trajectory values from baseline in the narrow banana odor plume and a clean air control for six flight parameters at and ms following plume contact.

To determine whether the short-term surge response to plume contact was maintained in the face of constant stimulation, flies were tested in a homogeneous plume of banana odor that was introduced upstream of the tunnel's working section. While smoke visualization indicated that the plume was as fully mixed as possible within the constraints of our apparatus, it is possible that the tunnel contained some spatial variation of odor density.

Nevertheless, in the face of the continuous stimulation, flies maintained the most consistently upwind flight headings that we observed under any condition Fig. In addition to flying very straight upwind, flies increased their upwind velocities relative to a clean-air control clean air: 0. The strength of this effect is further illustrated by comparison with representative trajectories in the ribbon plume of banana odor showing the surges along the plume as described above, as well as bouts of flight directed primarily cross-wind Fig.

These cross-wind excursions are reminiscent of the casting behavior of moths e. Kuenen and Baker, ; Marsh et al. Following plume contact, flies fly faster, straighter upwind. A Prior to plume contact, flight headings were distributed trimodally, with modes at 0. The shaded curve represents the trimodal model fit. B Following plume contact, flight was unimodally directed upwind 2.

For statistical analysis, mean pre-and post-contact headings were calculated for each fly. C Proportions of the total counts of instantaneous trajectory values for upwind velocity,air speed and plume distance. Plume contact results in trajectories oriented along the plume line.

A In the banana odor plume,pre-contact flight was largely directed across-wind whereas plume contact was followed by a shift towards upwind progress while maintaining close proximity to the plume-line with flies occasionally casting across wind.

Effects of contact with a ribbon plume of banana odor on kinematic parameters. The mean and standard error envelope are plotted for 1 s of flight prior to and following the first episode of plume contact in the banana odor ribbon plume yellow error envelope, flies and in a no odor control gray error envelope, 44 flies.

Because not all trajectories consisted of at least 1 s of flight prior to and following plume contact, means and standard errors were calculated at all time points from all trajectories whose durations met or exceeded that threshold length.

To assess the effects of plume loss on trajectory shape, flies were flown in a large diameter, pulsed banana plume. Pulses were generated for 1 s with a duty cycle. Furthermore, we required that during a cast, a fly must move a minimum of 3 cm across wind.

Although this definition is somewhat arbitrary, it effectively captures the qualitative difference in behavior that an observer can subjectively identify as a cast.

In a separate series of trials, flies were flown in the same large diameter plume, but with a continuous rather than a pulsed odor structure.

Our cast identification algorithm, in this case, searched for casts that initiated within the plume,allowing for the possibility that the cast itself would carry the animal outside of the plume.

In all cases, our analysis was restricted to the first episode of plume contact for each fly. In a homogeneous cloud, flight is directed almost completely upwind. A In a no odor control, wind polarized flight upwind 0.

Note that raw heading counts are plotted, but only mean trajectory headings are analyzed statistically. Upwind flight was also significantly faster in the homogeneous cloud d. Representative trajectories illustrate the differences between flight in a homogeneous cloud, clean air, and a banana odor ribbon plume. Flight in the homogeneous cloud often gave rise to very straight upwind trajectories compared to clean air.

Trajectories in clean air headed generally upwind,while those in the banana odor ribbon plume were largely characterized by upwind flight interspersed with cross-wind casts. In the pulsed plume, flies frequently initiated casts following plume truncation, whereas in the continuous plume, trajectories tended to consist of sustained periods of upwind flight with few casts initiated while the fly was still in the plume Fig.

The duration of plume contact could influence the likelihood of cast initiation, therefore we calculated the mean duration of contact prior to truncation of the pulsed plume Fig. We required that casts initiate with a latency of at least one frame These pools were further reduced when flies in the pulsed plume encountered subsequent odor pulses, or when flies in the continuous plume flew out of its boundaries.

The probability of cast initiation in each 50 ms bin following actual or pseudo-plume truncation was thus calculated as the number of flies that initiated casts within each bin divided by the number of flies in that bin that had not yet been excluded for any of the above reasons Fig. Implementing this correction, flies were significantly more likely to initiate a cast in the first second following truncation of a pulsed plume than after an equivalent period in a continuous plume d.

Following actual plume truncation, 17 flies In the continuous plume, only three flies 3. We performed an analogous, within-fly analysis, for flies that experienced plume truncation in the pulsed plume. Here we compared cast initiation following plume contact but while the fly still remained within the plume to casting following truncation of that plume Fig.

We calculated the probability of cast initiation in each 50 ms bin following plume contact as the number of flies that initiated casts within each bin divided by the number of flies that had not yet suffered plume truncation.

Casting probability following truncation was calculated as above. Following plume contact, three flies 7. Casting frequently follows plume truncation.

A Four representative trajectories from the large diameter pulsed banana odor plume illustrate flight prior to plume contact red , within the plume blue , and following plume loss due to truncation gray.

The first cast, as defined by our cast identification algorithm, is plotted in green. B In the continuous large diameter plume, casting rarely initiated within the plume color designations as above except that gray indicates plume loss due to flight out of the plume rather than plume truncation.

Arrows indicate the initiation of fly tracking,but in some cases several points were excised from the beginning of the track in order to enhance the clarity of the trajectory. Plume loss increases the probability of casting.

A To test the effect of plume truncation on the probability of cast initiation, we calculated the mean duration of contact with a pulsed plume prior to truncation ms.

B The probability of casting following plume truncation was compared to that following ms exposure to the continuous plume. Casting was significantly more likely following plume truncation than in the continuous plume d. For flies in the pulsed plume, cast initiation was significantly more likely following plume truncation Di than following plume contact Diii; d. Restricting our analysis to flies that initiated casts following plume truncation, post-contact trajectories were partitioned and aligned at the moment of cast initiation.

The effects of casting are largely the inverse of those elicited by plume contact Fig. Many of these effects are not surprising since they follow from the nature of the cast definition that is, a modification of heading. It is also apparent that the initiation of those turns which will eventually result in crosswind flight as judged from mean heading precede cast initiation, as defined above, by approximately 40 ms on average Fig.

A-F Effects of cast initiation on trajectory parameters. Kinematic parameters were aligned at the moment of cast initiation following plume loss due to truncation mean and envelope of standard deviation are plotted. The results of this study indicate that food-deprived D. Furthermore, in the presence of a medium strength wind 0. Previous studies on walking D. Theoretical arguments have suggested that flying insects should modulate their heading during olfactory search so as to maximize the likelihood of encountering an odor plume Balkovsky and Shraiman, ; Dusenberry, ; Sabelis and Schippers, The present data indicate that in the absence of an olfactory stimulus, D.

Zanen and co-workers, however, studied flies in a wider 1 m tunnel with a square footprint, and it is possible that the relatively narrow dimensions of our working section may have sufficiently inhibited cross-wind flight to mask such effects.

On the other hand, flies did perform casts in our tunnel, indicating that the visual environment did not inhibit all cross-wind behavior. Presumably, anemotaxis in D. Furthermore, the anemotactic response inhibits some visually mediated behaviors, including the otherwise robust attraction to conspicuous visual objects Fig. At the same time,anemotaxis does not universally suppress other mechanisms of visual guidance.

For instance, while flying upwind, D. This suggests that flies, like bees, may balance the optic flow on both eyes in order to remain equidistant from the tunnel walls. At the same time, flies were not limited to flight tracks that strictly followed the tunnel's midline and were somewhat dispersed across the width of the tunnel. Many flies did not head straight upwind, but instead repeatedly approached the walls, sometimes exhibiting saccadic maneuvers that are conspicuous in still air Tammero and Dickinson, This suggests that expansion avoidance cues, generated by approach towards the tunnel walls, were also important in maintaining the flies' upwind heading,together with the anemotactic response.

In the presence of a ribbon plume of an attractive odor, pre-contact flight headings were trimodally distributed, with modal values at upwind and cross-wind headings Fig. Thus, whereas search trajectories did not seem to be directed across-wind in the absence of odor,following plume contact and likely subsequent loss , flies initiated a qualitatively different sort of search behavior, mediated by casts, and which did frequently result in subsequent plume contact.

These results suggest that D. In recent years, our understanding of olfactory-mediated search in insects has improved substantially.

This finding makes it realistic to imagine that a comprehensive understanding of short-term stimulus responses could be adequate to explain the emergent behavior. Baker has articulated an elegant model for olfactory flight control Baker, , whereby a phasically modulated response to plume contact generates an upwind surge and a separate, tonic response, activates an internal counterturn generating mechanism. Suppression of the tonic mechanism by the phasic one in response to a pulsed plume of the appropriate frequency could result in an iterated series of upwind surges, fusing to form straight upwind flight.

While it nicely explains the results of many experiments on moths, the applicability of Baker's model to flight in other insect orders is still unclear. In this study, we found that D. Skip to main content. Listed in category:. Email to friends Share on Facebook - opens in a new window or tab Share on Twitter - opens in a new window or tab Share on Pinterest - opens in a new window or tab. Add to Watchlist. People who viewed this item also viewed.

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