Visual approach computation in feeding hoverflies.

On warm sunny days, female hoverflies are often observed feeding from a wide range of wild and cultivated flowers. In doing so, hoverflies serve a vital role as alternative pollinators, and are suggested to be the most important pollinators after bees and bumblebees. Unless the flower hoverflies are feeding from is large, they do not readily share the space with other insects, but instead opt to leave if another insect approaches. We used high-speed videography followed by 3D reconstruction of flight trajectories to quantify how female Eristalis hoverflies respond to approaching bees, wasps and two different hoverfly species. We found that, in 94% of the interactions, the occupant female left the flower when approached by another insect. We found that compared with spontaneous take-offs, the occupant hoverfly's escape response was performed at ∼3 times higher speed (spontaneous take-off at 0.2±0.05 m s-1 compared with 0.55±0.08 m s-1 when approached by another Eristalis). The hoverflies tended to take off upward and forward, while taking the incomer's approach angle into account. Intriguingly, we found that, when approached by wasps, the occupant Eristalis took off at a higher speed and when the wasp was further away. This suggests that feeding hoverflies may be able to distinguish these predators, demanding impressive visual capabilities. Our results, including quantification of the visual information available before occupant take-off, provide important insight into how freely behaving hoverflies perform escape responses from competitors and predators (e.g. wasps) in the wild.This work was funded by the Air Force Office of Scientific Research (FA9550-15-1-0188 to P.T. Gonzalez-Bellido and K. Nordström), the Biotechnology and Biological Sciences Research Council (BB/L024667/1 David Phillips Fellowship to T. Wardill), Australian Research Council (DP170100008), Stiftelsen Olle Engkvist Byggmästare (2016/348) and Stiftelsen Längmanska Kulturfonden (BA17-0812)

A behavioural investigation into Eristalis tenax : Pursuit, approach estimation, locomotor activity and rearing

Hoverflies are suggested to be the 2nd most important pollinator group after bees and bumblebees, and with the changing climate and dwindling numbers of pollinators it might never have been more important understanding our pollinators. Given the hoverflies’ small brains, beautiful aerial acrobatics, good temporal resolution, but limited spatial resolution, these flies make interesting study animals for flight behaviour and vision research. Eristalis tenax hoverflies are globally spread generalist pollinators, thus well suited for studies internationally. However, due to weather and behavioural seasonality, the hoverflies can be hard to access all year round. Furthermore, only observational studies have been performed to investigate their activity rhythm, and neither pursuit behaviour nor interactions with other insects are well studied. We therefore developed a new protocol for rearing E. tenax, and by adding artificial hibernation we managed to get the hoverflies to survive up to a year – making the hoverflies accessible all year round. Using LAMS, we confirmed earlier suggestions that E. tenax are diurnal, and also showed that they are active during the entire light phase of an LD cycle. We also found that the hoverflies locomotor activity is remarkably robust – it was not affected by age, diet or starvation. However, an accompanying conspecific did affect the locomotor activity. Using high speed videography in the field we found that female Eristalis are affected by the presence of other insects outdoors as well. The females escaped their food flowers 94 % of the times they were approached, even though only 16 % of the incomers were potentially dangerous wasps. Interestingly, the females seemed to be able to distinguish between wasps and other incomers, leaving the flowers earlier and at a higher speed when approached by wasps. Bringing our high-speed cameras indoors we developed a flight arena, allowing for studies of eristaline flight behaviour all year round. Using this setup, we found that male E. tenax pursue beads 6 - 38.5 mm in diameter traveling at 0 - 1.8 ms-1. Fascinatingly, we found that the flies pursued the beads from both below and above, often keeping the target outside their bright zone

A behavioural investigation into Eristalis tenax : Pursuit, approach estimation, locomotor activity and rearing

Hoverflies are suggested to be the 2nd most important pollinator group after bees and bumblebees, and with the changing climate and dwindling numbers of pollinators it might never have been more important understanding our pollinators. Given the hoverflies’ small brains, beautiful aerial acrobatics, good temporal resolution, but limited spatial resolution, these flies make interesting study animals for flight behaviour and vision research. Eristalis tenax hoverflies are globally spread generalist pollinators, thus well suited for studies internationally. However, due to weather and behavioural seasonality, the hoverflies can be hard to access all year round. Furthermore, only observational studies have been performed to investigate their activity rhythm, and neither pursuit behaviour nor interactions with other insects are well studied. We therefore developed a new protocol for rearing E. tenax, and by adding artificial hibernation we managed to get the hoverflies to survive up to a year – making the hoverflies accessible all year round. Using LAMS, we confirmed earlier suggestions that E. tenax are diurnal, and also showed that they are active during the entire light phase of an LD cycle. We also found that the hoverflies locomotor activity is remarkably robust – it was not affected by age, diet or starvation. However, an accompanying conspecific did affect the locomotor activity. Using high speed videography in the field we found that female Eristalis are affected by the presence of other insects outdoors as well. The females escaped their food flowers 94 % of the times they were approached, even though only 16 % of the incomers were potentially dangerous wasps. Interestingly, the females seemed to be able to distinguish between wasps and other incomers, leaving the flowers earlier and at a higher speed when approached by wasps. Bringing our high-speed cameras indoors we developed a flight arena, allowing for studies of eristaline flight behaviour all year round. Using this setup, we found that male E. tenax pursue beads 6 - 38.5 mm in diameter traveling at 0 - 1.8 ms-1. Fascinatingly, we found that the flies pursued the beads from both below and above, often keeping the target outside their bright zone

Data from: Hoverfly locomotor activity is resilient to external influence and intrinsic factors

Hoverflies are found across the globe, with approximately 6000 species described worldwide. Many hoverflies are being used in agriculture and some are emerging as model species for laboratory experiments. As such it is valuable to know more about their activity. Like many other dipteran flies, Eristalis hoverflies have been suggested to be strongly diurnal, but this is based on qualitative visualization by human observers. To quantify how hoverfly activity depends on internal and external factors, we here utilize a locomotor activity monitoring system. We show that Eristalis hoverflies are active during the entire light period when exposed to a 12 h light:12 h dark cycle, with a lower activity if exposed to light during the night. We show that the hoverflies’ locomotor activity is stable over their lifetime and that it does not depend on the diet provided. Surprisingly, we find no difference in activity between males and females, but the activity is significantly affected by the sex of an accompanying conspecific. Finally, we show that female hoverflies are more resilient to starvation than males. In summary, Eristalis hoverflies are resilient to a range of internal and external factors, supporting their use in long-term laboratory experiments

Raw_tracks_predator_trials

Raw ctrax output (after manual correction) for predator model trials

Data from: Visual approach computation in feeding hoverflies

On warm sunny days female hoverflies are often observed feeding from a wide range of wild and cultivated flowers. In doing so, hoverflies serve a vital role as alternative pollinators, and suggested to be the most important after bees and bumblebees. Unless the flower hoverflies are feeding from is large, they do not readily share the space with other insects, but instead opt to leave. We have used high-speed videography followed by 3D reconstruction of flight trajectories to quantify how female Eristalis hoverflies respond to approaching bees, wasps and two different hoverfly species. We found that in 94% of the interactions the occupant female left the flower when approached by another insect. We found that compared to spontaneous take-offs, the occupant hoverfly's escape response was performed at ca. 3 times higher speed (spontaneous take-off at 0.2 +/- 0.05 m/s compared with 0.55 +/- 0.08 m/s when approached by another Eristalis). The hoverflies tended to take off upward and forward, while taking the incomer's approach angle into account. Intriguingly, we found when approached by wasps that the occupant Eristalis took off at a higher speed and when the wasp was further away. This suggests that feeding hoverflies may be able to distinguish these predators, demanding impressive visual capabilities. Our results, including quantification of the visual information available before occupant take-off, provide important insight into how freely behaving hoverflies perform escape responses from competitors and predators (e.g. wasps) in the wild

The terminal basal mitosis of chicken retinal Lim1 horizontal cells is not sensitive to cisplatin-induced cell cycle arrest

For proper development, cells need to coordinate proliferation and cell cycle-exit. This is mediated by a cascade of proteins making sure that each phase of the cell cycle is controlled before the initiation of the next. Retinal progenitor cells divide during the process of interkinetic nuclear migration, where they undergo S-phase on the basal side, followed by mitoses on the apical side of the neuroepithelium. The final cell cycle of chicken retinal horizontal cells (HCs) is an exception to this general cell cycle behavior. Lim1 expressing (+) horizontal progenitor cells (HPCs) have a heterogenic final cell cycle, with some cells undergoing a terminal mitosis on the basal side of the retina. The results in this study show that this terminal basal mitosis of Lim1+ HPCs is not dependent on Chk1/2 for its regulation compared to retinal cells undergoing interkinetic nuclear migration. Neither activating nor blocking Chk1 had an effect on the basal mitosis of Lim1+ HPCs. Furthermore, the Lim1+ HPCs were not sensitive to cisplatin-induced DNA damage and were able to continue into mitosis in the presence of γ-H2AX without activation of caspase-3. However, Nutlin3a-induced expression of p21 did reduce the mitoses, suggesting the presence of a functional p53/p21 response in HPCs. In contrast, the apical mitoses were blocked upon activation of either Chk1/2 or p21, indicating the importance of these proteins during the process of interkinetic nuclear migration. Inhibiting Cdk1 blocked M-phase transition both for apical and basal mitoses. This confirmed that the cyclin B1-Cdk1 complex was active and functional during the basal mitosis of Lim1+ HPCs. The regulation of the final cell cycle of Lim1+ HPCs is of particular interest since it has been shown that the HCs are able to sustain persistent DNA damage, remain in the cell cycle for an extended period of time and, consequently, survive for months

Data from: Brain size affects the behavioral response to predators in female guppies (Poecilia reticulata)

Large brains are thought to result from selection for cognitive benefits, but how enhanced cognition leads to increased fitness remains poorly understood. One explanation is that increased cognitive ability results in improved monitoring and assessment of predator threats. Here, we use male and female guppies (Poecilia reticulata), artificially selected for large and small brain size, to provide an experimental evaluation of this hypothesis. We examined their behavioural response as singletons, pairs or shoals of four towards a model predator. Large-brained females, but not males, spent less time performing predator inspections, an inherently risky behaviour. Video analysis revealed that large-brained females were further away from the model predator when in pairs but that they habituated quickly towards the model when in shoals of four. Males stayed further away from the predator model than females but again we found no brain size effect in males. We conclude that differences in brain size affect the female predator response. Large-brained females might be able to assess risk better or need less sensory information to reach an accurate conclusion. Our results provide experimental support for the general idea that predation pressure is likely to be important for the evolution of brain size in prey species

Processed_tracks

Location and orientation data (video tracking) for both predator and control trials, after processing