Trevor Wardill | University of Minnesota - Twin Cities (original) (raw)

Papers by Trevor Wardill

Current Biology, Jun 1, 2023

Molecular Ecology Notes, Sep 1, 2004

Five microsatellite loci are presented for prickly acacia, Acacia nilotica ssp. indica (Benth.) B... more Five microsatellite loci are presented for prickly acacia, Acacia nilotica ssp. indica (Benth.) Brenan, an introduced weed of national significance in Australia. These microsatellite loci were obtained through the construction of an enriched library and their use will enable us to determine the genetic origin and extent of genetic diversity of this weed in Australia.

The supporting data include microscopy images, quantitative analyses of images, and statistical a... more The supporting data include microscopy images, quantitative analyses of images, and statistical analyses, for each figure presented in the linked paper. See the Readme.pdf file for a detailed description of the contents of each folder and for a list of file formats.Listed in DOI: 10.3389/fnins.2020.0081

The Journal of Experimental Biology, Feb 15, 2023

The ability to visualize small moving objects is vital for the survival of many animals, as these... more The ability to visualize small moving objects is vital for the survival of many animals, as these could represent predators or prey. For example, predatory insects, including dragonflies, robber flies and killer flies, perform elegant, high-speed pursuits of both biological and artificial targets. Many non-predatory insects, including male hoverflies and blowflies, also pursue targets during territorial or courtship interactions. To date, most hoverfly pursuits were studied outdoors. To investigate naturalistic hoverfly (Eristalis tenax) pursuits under more controlled settings, we constructed an indoor arena that was large enough to encourage naturalistic behavior. We presented artificial beads of different sizes, moving at different Journal of Experimental Biology • Accepted manuscript speeds, and filmed pursuits with two cameras, allowing subsequent 3D reconstruction of the hoverfly and bead position as a function of time. We show that male E. tenax hoverflies are unlikely to use strict heuristic rules based on angular size or speed to determine when to start pursuit, at least in our indoor setting. We found that hoverflies pursued faster beads when the trajectory involved flying downwards towards the bead. Furthermore, we show that target pursuit behavior can be broken down into two stages. In the first stage the hoverfly attempts to rapidly decreases the distance to the target by intercepting it at high speed. During the second stage the hoverfly's forward speed is correlated with the speed of the bead, so that the hoverfly remains close, but without catching it. This may be similar to dragonfly shadowing behavior, previously coined 'motion camouflage'. AB (Sollentuna, Sweden). The arena was lit from above by two daylight fluorescent lamps (58 W/865, Nova Group AB, Helsingborg, Sweden) and two office fluorescent lamps, giving an average illuminance of 900-1200 lux (LM-120 Light Meter, Amprobe, Everet, WA, USA). The hoverflies were kept at a 12:12 light:dark cycle at room temperature (19-20°C). A fishing line (0.3 mm diameter) was looped around the arena, entering horizontally through two holes at 0.7 m height (Fig. 1A, Movie S1-3), with a bead attached using a 0.06 mm diameter fishing line. A laptop controlled a stepper motor via a stepper driver (23HS-108 MK.2 Stepper motor and ST5-Q-NN DC input stepper driver, Promoco Scandinavia AB,

Frontiers in Neuroscience, Aug 10, 2020

Genes for endoplasmic reticulum (ER)-shaping proteins are among the most commonly mutated in here... more Genes for endoplasmic reticulum (ER)-shaping proteins are among the most commonly mutated in hereditary spastic paraplegia (HSP). Mutation of these genes in model organisms can lead to disruption of the ER network. To investigate how the physiological roles of the ER might be affected by such disruption, we developed tools to interrogate its Ca 2+ signaling function. We generated GAL4-driven Ca 2+ sensors targeted to the ER lumen, to record ER Ca 2+ fluxes in identified Drosophila neurons. Using GAL4 lines specific for Type Ib or Type Is larval motor neurons, we compared the responses of different lumenal indicators to electrical stimulation, in axons and presynaptic terminals. The most effective sensor, ER-GCaMP6-210, had a Ca 2+ affinity close to the expected ER lumenal concentration. Repetitive nerve stimulation generally showed a transient increase of lumenal Ca 2+ in both the axon and presynaptic terminals. Mutants lacking neuronal reticulon and REEP proteins, homologs of human HSP proteins, showed a larger ER lumenal evoked response compared to wild type; we propose mechanisms by which this phenotype could lead to neuronal dysfunction or degeneration. Our lines are useful additions to a Drosophila Ca 2+ imaging toolkit, to explore the physiological roles of ER, and its pathophysiological roles in HSP and in axon degeneration more broadly.

Molecular Ecology Notes, Sep 1, 2004

Twelve microsatellite loci are presented for the biological control agent Chiasmia assimilis (War... more Twelve microsatellite loci are presented for the biological control agent Chiasmia assimilis (Warren, 1899). These microsatellite loci were obtained through the construction of an enriched library, overcoming previous reported difficulties with obtaining microsatellites from other Lepidoptera due to the low frequency of microsatellites in their genomes.

The Journal of Experimental Biology, Feb 15, 2022

The miniature robber fly Holcocephala fusca intercepts its targets with behaviour that is approxi... more The miniature robber fly Holcocephala fusca intercepts its targets with behaviour that is approximated by the proportional navigation guidance law. During predatory trials, we challenged the interception of H. fusca performance by placing a large object in its potential flight path. In response, H. fusca deviated from the path predicted by pure proportional navigation, but in many cases still eventually contacted the target. We show that such flight deviations can be explained as the output of two competing navigational systems: pure-proportional navigation and a simple obstacle avoidance algorithm. Obstacle avoidance by H. fusca is here described by a simple feedback loop that uses the visual expansion of the approaching obstacle to mediate the magnitude of the turningaway response. We name the integration of this steering law with proportional navigation 'combined guidance'. The results demonstrate that predatory intent does not operate a monopoly on the fly's steering when attacking a target, and that simple guidance combinations can explain obstacle avoidance during interceptive tasks.

PLOS ONE, Jan 30, 2009

Because of the limited processing capacity of eyes, retinal networks must adapt constantly to bes... more Because of the limited processing capacity of eyes, retinal networks must adapt constantly to best present the ever changing visual world to the brain. However, we still know little about how adaptation in retinal networks shapes neural encoding of changing information. To study this question, we recorded voltage responses from photoreceptors (R1-R6) and their output neurons (LMCs) in the Drosophila eye to repeated patterns of contrast values, collected from natural scenes. By analyzing the continuous photoreceptor-to-LMC transformations of these graded-potential neurons, we show that the efficiency of coding is dynamically improved by adaptation. In particular, adaptation enhances both the frequency and amplitude distribution of LMC output by improving sensitivity to under-represented signals within seconds. Moreover, the signal-to-noise ratio of LMC output increases in the same time scale. We suggest that these coding properties can be used to study network adaptation using the genetic tools in Drosophila, as shown in a companion paper (Part II).

Genes for ER-shaping proteins are among the most commonly mutated in Hereditary Spastic Paraplegi... more Genes for ER-shaping proteins are among the most commonly mutated in Hereditary Spastic Paraplegia (HSP). Mutation of these genes in model organisms can lead to disruption of the ER network. To investigate how the physiological roles of the ER might be affected by such disruption, we developed tools to interrogate its Ca 2+ signaling function. We generated GAL4-driven Ca 2+ sensors targeted to the ER lumen, to record ER Ca 2+ fluxes in identified Drosophila neurons. Using GAL4 lines specific for Type Ib or Type Is larval motor neurons, we compared the responses of different lumenal indicators to electrical stimulation, in axons and presynaptic terminals. The most effective sensor, ER-GCaMP6-210, had a Ca 2+ affinity close to the expected ER lumenal concentration. Repetitive nerve stimulation generally showed a transient increase of lumenal Ca 2+ in both the axon and presynaptic terminals. Mutants lacking neuronal reticulon and REEP proteins, homologs of human HSP proteins, showed a larger ER lumenal evoked response compared to wild type; we propose mechanisms by which this phenotype could lead to neuronal dysfunction or degeneration. Our lines are useful additions to a Drosophila Ca 2+ imaging toolkit, to explore the physiological roles of ER, and its pathophysiological roles in HSP and in axon degeneration more broadly.

Molecular Biology and Evolution

The evolutionary history of visual genes in Coleoptera differs from other well-studied insect ord... more The evolutionary history of visual genes in Coleoptera differs from other well-studied insect orders, such as Lepidoptera and Diptera, as beetles have lost the widely conserved short-wavelength (SW) insect opsin gene that typically underpins sensitivity to blue light (∼440 nm). Duplications of the ancestral ultraviolet (UV) and long-wavelength (LW) opsins have occurred in many beetle lineages and have been proposed as an evolutionary route for expanded spectral sensitivity. The jewel beetles (Buprestidae) are a highly ecologically diverse and colorful family of beetles that use color cues for mate and host detection. In addition, there is evidence that buprestids have complex spectral sensitivity with up to five photoreceptor classes. Previous work suggested that opsin duplication and subfunctionalization of the two ancestral buprestid opsins, UV and LW, has expanded sensitivity to different regions of the light spectrum, but this has not yet been tested. We show that both duplicati...

Why Velcro 3D glasses onto cuttlefish? In Episode 69, Trevor Wardill from the Department of Ecolo... more Why Velcro 3D glasses onto cuttlefish? In Episode 69, Trevor Wardill from the Department of Ecology, Evolution and Behavior at the University of Minnesota discusses his research into the previously unknown ability of the cephalopod to see in stereo vision. His article, "Cuttlefish use stereopsis to strike at prey," was published along with multiple co-authors on January 8, 2020 in the journal Science Advances. https://www.parsingscience.org/2020/03/03/trevor-wardill/

This thesis addresses two aspects of visual processing in two different invertebrate organisms. T... more This thesis addresses two aspects of visual processing in two different invertebrate organisms. The fruit fly, Drosophila melanogaster, has emerged as a key model for invertebrate vision research. Despite extensive characterisation of motion vision, very little is known about how flies process colour information, or how the spectral content of light affects other visual modalities. With the aim to accurately dissect the different components of the Drosophila visual system responsible for processing colour, I have developed a versatile visual stimulation setup to probe for the combinations of spatial, temporal and spectral visual response properties. Using flies that express neural activity indicators, I can track visual responses to a colour stimulus (i.e. narrow bands of light across the spectrum) via a two-photon imaging system. The visual stimulus is projected on a specialised screen material that scatters wavelengths of light across the spectrum equally at all locations of the screen, thus enabling presentation of spatially structured stimuli. Using this setup, I have characterised spectral responses, intensity-response relationships, and receptive fields of neurons in the early visual system of a variety of genetically modified strains of Drosophila. Specifically, I compared visual responses in the medulla of flies expressing either a subset or all photoreceptor opsins, with differing levels of screening pigment present in the eye. I found layer-specific shifts of spectral response properties correlating with projection regions of photoreceptor terminals. I also 3 found that a reduction in screening pigment shifts the general spectral response in the neuropil towards the longer wavelengths of light. I have also mapped receptive fields across the different layers of the medulla for the peak spectral response wavelength. My results suggest that receptive field dimensions match the expected size predicted by the conservation of a columnar organisation in the medulla, with little variation from layer to layer. I [...]

Highlights • Holcocephala fusca robber flies capture prey with a constant bearing angle strategy ... more Highlights • Holcocephala fusca robber flies capture prey with a constant bearing angle strategy • The approach is proactively altered to “lock-on” on to prey within 29 cm distance • The retina spatial resolution is 0.28°, but the object detection threshold is 0.13° • The fly’s stereopsis range is estimated to be ~26 cm eTOC blurb Robber flies are aerial predators. Here, Wardill and Fabian et al. show that the tiny robber fly Holcocephala fusca attacks a detected prey reactively, but proactively changes its speed and direction when the prey is within 30 cm. They also show that the very small object detection threshold of 1.3o is supported by a striking visual fovea Data included here is the supplemental data figures and main figures. As the raw dataset is over 10 TB it cannot be offered here or elsewhere. Please contact the authors for obtaining such volumes of data.

Proceedings of the National Academy of Sciences, 2016

Brain, behavior and evolution, Jan 24, 2015

Predatory animals have evolved to optimally detect their prey using exquisite sensory systems suc... more Predatory animals have evolved to optimally detect their prey using exquisite sensory systems such as vision, olfaction and hearing. It may not be so surprising that vertebrates, with large central nervous systems, excel at predatory behaviors. More striking is the fact that many tiny insects, with their miniscule brains and scaled down nerve cords, are also ferocious, highly successful predators. For predation, it is important to determine whether a prey is suitable before initiating pursuit. This is paramount since pursuing a prey that is too large to capture, subdue or dispatch will generate a substantial metabolic cost (in the form of muscle output) without any chance of metabolic gain (in the form of food). In addition, during all pursuits, the predator breaks its potential camouflage and thus runs the risk of becoming prey itself. Many insects use their eyes to initially detect and subsequently pursue prey. Dragonflies, which are extremely efficient predators, therefore have h...

PloS one, 2015

Cephalopods are famous for their ability to change color and pattern rapidly for signaling and ca... more Cephalopods are famous for their ability to change color and pattern rapidly for signaling and camouflage. They have keen eyes and remarkable vision, made possible by photoreceptors in their retinas. External to the eyes, photoreceptors also exist in parolfactory vesicles and some light organs, where they function using a rhodopsin protein that is identical to that expressed in the retina. Furthermore, dermal chromatophore organs contain rhodopsin and other components of phototransduction (including retinochrome, a photoisomerase first found in the retina), suggesting that they are photoreceptive. In this study, we used a modified whole-mount immunohistochemical technique to explore rhodopsin and retinochrome expression in a number of tissues and organs in the longfin squid, Doryteuthis pealeii. We found that fin central muscles, hair cells (epithelial primary sensory neurons), arm axial ganglia, and sucker peduncle nerves all express rhodopsin and retinochrome proteins. Our finding...

Current Biology, Jun 1, 2023

Molecular Ecology Notes, Sep 1, 2004

The Journal of Experimental Biology, Feb 15, 2023

Frontiers in Neuroscience, Aug 10, 2020

Molecular Ecology Notes, Sep 1, 2004

The Journal of Experimental Biology, Feb 15, 2022

PLOS ONE, Jan 30, 2009

Molecular Biology and Evolution

Proceedings of the National Academy of Sciences, 2016

Brain, behavior and evolution, Jan 24, 2015

PloS one, 2015