Sonar Beam Direction and Flight Control in an Echolocating Bat

Echolocating insectivorous bats are nocturnal mammals that capture fast, erratically moving insects in flight. Bats emit short ultrasonic pulses that form beams of sound and use the returning echoes to guide behavior. The frequency, duration and timing of the sonar pulses, along with the spatial direction of the sonar beam restrict the information returning to the bat, and can be considered a component of the acoustic gaze of bats. A great deal is known about the time-frequency structure of bat echolocation calls and their relationship to the stages of foraging flight in bats. It is however not known how bats direct their sonar beam in flight or how beam direction is related to flight control. This is the first study of the sonar beam direction in freely flying bats as they chase and capture insects. An apparatus and method to measure the sonar beam pattern of echolocating bats (<it>Eptesicus fuscus</it>, big brown bats) as they fly in a laboratory flight room is described. It is shown that the bat locks its sonar beam tightly onto a target during pursuit (Chapter 2). The flying bat's sonar beam consists of two lobes directed apart in the vertical plane (Chapter 3). There is a coupling between acoustic gaze (sonar beam axis) direction and flight turn rate that can be expressed as a delayed linear control law. The gain of this law (steepness of the relationship) varies with the bat's behavioral state (Chapter 4). The bat, when pursuing erratically flying insects, adopts a strategy that keeps the absolute direction to the target a constant. This strategy is shown, under some assumptions, to minimize time-to-intercept of erratically maneuvering targets and is similar to parallel navigation implemented in guided missiles (Chapter 5). The bat is not helpless against ultrasound-triggered evasive dives evolved by some hearing insects. The bat adopts flight strategies to counter such dives (Chapter 6). This work allows us to compare spatial behaviors well studied in visual animals, with similar behaviors in an animal that is guided by hearing and make inferences about common computational strategies employed by nervous systems

Sonar Beam Direction and Flight Control in an Echolocating Bat

Echolocating insectivorous bats are nocturnal mammals that capture fast, erratically moving insects in flight. Bats emit short ultrasonic pulses that form beams of sound and use the returning echoes to guide behavior. The frequency, duration and timing of the sonar pulses, along with the spatial direction of the sonar beam restrict the information returning to the bat, and can be considered a component of the acoustic gaze of bats. A great deal is known about the time-frequency structure of bat echolocation calls and their relationship to the stages of foraging flight in bats. It is however not known how bats direct their sonar beam in flight or how beam direction is related to flight control. This is the first study of the sonar beam direction in freely flying bats as they chase and capture insects. An apparatus and method to measure the sonar beam pattern of echolocating bats (<it>Eptesicus fuscus</it>, big brown bats) as they fly in a laboratory flight room is described. It is shown that the bat locks its sonar beam tightly onto a target during pursuit (Chapter 2). The flying bat's sonar beam consists of two lobes directed apart in the vertical plane (Chapter 3). There is a coupling between acoustic gaze (sonar beam axis) direction and flight turn rate that can be expressed as a delayed linear control law. The gain of this law (steepness of the relationship) varies with the bat's behavioral state (Chapter 4). The bat, when pursuing erratically flying insects, adopts a strategy that keeps the absolute direction to the target a constant. This strategy is shown, under some assumptions, to minimize time-to-intercept of erratically maneuvering targets and is similar to parallel navigation implemented in guided missiles (Chapter 5). The bat is not helpless against ultrasound-triggered evasive dives evolved by some hearing insects. The bat adopts flight strategies to counter such dives (Chapter 6). This work allows us to compare spatial behaviors well studied in visual animals, with similar behaviors in an animal that is guided by hearing and make inferences about common computational strategies employed by nervous systems

Echolocating Bats Use a Nearly Time-Optimal Strategy to Intercept Prey

Acquisition of food in many animal species depends on the pursuit and capture of moving prey. Among modern humans, the pursuit and interception of moving targets plays a central role in a variety of sports, such as tennis, football, Frisbee, and baseball. Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion—such as a ballistic baseball, or a piece of food sinking in water. Many animals, however, have to capture prey that may make evasive and unpredictable maneuvers. Is CB an optimum solution to pursuing erratically moving targets? Do animals faced with such erratic prey also use CB? In this paper, we address these questions by studying prey capture in an insectivorous echolocating bat. Echolocating bats rely on sonar to pursue and capture flying insects. The bat's prey may emerge from foliage for a brief time, fly in erratic three-dimensional paths before returning to cover. Bats typically take less than one second to detect, localize and capture such insects. We used high speed stereo infra-red videography to study the three dimensional flight paths of the big brown bat, Eptesicus fuscus, as it chased erratically moving insects in a dark laboratory flight room. We quantified the bat's complex pursuit trajectories using a simple delay differential equation. Our analysis of the pursuit trajectories suggests that bats use a constant absolute target direction strategy during pursuit. We show mathematically that, unlike CB, this approach minimizes the time it takes for a pursuer to intercept an unpredictably moving target. Interestingly, the bat's behavior is similar to the interception strategy implemented in some guided missiles. We suggest that the time-optimal strategy adopted by the bat is in response to the evolutionary pressures of having to capture erratic and fast moving insects

Exploring the association between eating a whole food plant-based diet and reducing chronic diseases: a critical literature synthesis

Nearly 70% of the population of the United States is at increased risk for chronic illness because of dietary related health conditions. Half of all adults, 117 million people, have one or more preventable diet associated chronic diseases. The current state of the nation’s health is a serious public health concern as 1.5 million Americans die annually due to conditions related to dietary intake. The risks for chronic disease, such as obesity, are greater for segments of the population unable to afford healthier, nutritionally-dense food, especially low populations with low socioeconomic status and communities of color. This has created serious and significant health inequities. In the United States, healthcare spending accounts for more than 17% of the US economy. Chronic diseases, related conditions, and the health risk behaviors that cause them now account for most health care costs making these diseases a significant public health concern. Eighty-six percent of all health care spending in 2010 was for people with one or more chronic medical conditions. A literature search was conducted in SCOPUS and PubMed to address the following re-search question: Is there an association between eating a whole food plant-based diet and reduced rates of chronic diseases? This thesis examines the effects of eating a WFPB diet on the risk of chronic diseases and the prevention and mitigation of chronic diseases after diagnosis. Increasing the dietary intake of whole plant-based diet may help to prevent, reduce or even reverse certain chronic illnesses in the population. A diet consisting largely of unprocessed or primarily unprocessed healthy vegetables, fruits, whole grains, legumes, and beans might enable the US population to address the hyper-endemic level of chronic illnesses that have resulted from more than 40 years of eating the Western or Standard American Diet (SAD). These results have public health significance because they may help future researchers, public health and medical professionals, and policymakers as they look toward addressing and reducing the level of diet-related illnesses among the population, especially those who regularly experience health inequities

Structural and Dynamic Features of F-recruitment Site Driven Substrate Phosphorylation by ERK2

The F-recruitment site (FRS) of active ERK2 binds F-site (Phe-x-Phe-Pro) sequences found downstream of the Ser/Thr phospho-acceptor on cellular substrates. Here we apply NMR methods to analyze the interaction between active ERK2 (ppERK2), and a 13-residue F-site-bearing peptide substrate derived from its cellular target, the transcription factor Elk-1. Our results provide detailed insight into previously elusive structural and dynamic features of FRS/F-site interactions and FRS-driven substrate phosphorylation. We show that substrate F-site engagement significantly quenches slow dynamics involving the ppERK2 activation-loop and the FRS. We also demonstrate that the F-site phenylalanines make critical contacts with ppERK2, in contrast to the proline whose cis-trans isomerization has no significant effect on F-site recognition by the kinase FRS. Our results support a mechanism where phosphorylation of the disordered N-terminal phospho-acceptor is facilitated by its increased productive encounters with the ppERK2 active site due to docking of the proximal F-site at the kinase FRS

Induced Mutagenesis in UGT74S1 Gene Leads to Stable New Flax Lines with Altered Secoisolariciresinol Diglucoside (SDG) Profiles

Flax secoisolariciresinol (SECO) diglucoside (SDG) lignan is an emerging natural product purported to prevent chronic diseases in humans. SECO, the aglycone form of SDG, has shown higher intestinal cell absorption but it is not accumulated naturally in planta. Recently, we have identified and characterized a UDP-glucosyltransferase gene, UGT74S1, that glucosylates SECO into its monoglucoside (SMG) and SDG forms when expressed in yeast. However, whether this gene is unique in controlling SECO glucosylation into SDG in planta is unclear. Here, we report on the use of UGT74S1 in reverse and forward genetics to characterize an ethyl methane sulfonate (EMS) mutagenized flax population from cultivar CDC Bethune and consisting of 1996 M2 families. EMS mutagenesis generated 73 SNP variants causing 79 mutational events in the UGT74S1 exonic regions of 93 M2 families. The mutation frequency in the exonic regions was determined to be one per 28 Kb. Of these mutations, 13 homozygous missense mutations and two homozygous nonsense mutations were observed and all were transmitted into the M3 and M4 generations. Forward genetics screening of the population showed homozygous nonsense mutants completely lacking SDG biosynthesis while the production of SMG was observed only in a subset of the M4 lines. Heterozygous or homozygous M4 missense mutants displayed a wide range of SDG levels, some being greater than those of CDC Bethune. No additional deleterious mutations were detected in these mutant lines using a panel of 10 other genes potentially involved in the lignan biosynthesis. This study provides further evidence that UGT74S1 is unique in controlling SDG formation from SECO and this is the first report of non-transgenic flax germplasm with simultaneous knockout of SDG and presence of SMG in planta