Movement of individual organisms is fundamental to life, quilting our planet in a rich tapestry of phenomena with diverse implications for ecosystems and humans. Movement research is both plentiful and insightful, and recent methodological advances facilitate obtaining a detailed view of individual movement. Yet, we lack a general unifying paradigm, derived from first principles, which can place movement studies within a common context and advance the development of a mature scientific discipline. This introductory article to the Movement Ecology Special Feature proposes a paradigm that integrates conceptual, theoretical, methodological, and empirical frameworks for studying movement of all organisms, from microbes to trees to elephants. We introduce a conceptual framework depicting the interplay among four basic mechanistic components of organismal movement: the internal state (why move?), motion (how to move?), and navigation (when and where to move?) capacities of the individual and the external factors affecting movement. We demonstrate how the proposed framework aids the study of various taxa and movement types; promotes the formulation of hypotheses about movement; and complements existing biomechanical, cognitive, random, and optimality paradigms of movement. The proposed framework integrates eclectic research on movement into a structured paradigm and aims at providing a basis for hypothesis generation and a vehicle facilitating the understanding of the causes, mechanisms, and spatiotemporal patterns of movement and their role in various ecological and evolutionary processes. "Now we must consider in general the common reason for moving with any movement whatever." (Aristotle, De Motu Animalium, 4th century B.C.).

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A movement ecology paradigm for unifying organismal movement research

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

For centuries, flow visualization has been the art of making fluid motion visible in physical and biological systems. Although such flow patterns can be, in principle, described by the Navier-Stokes equations, extracting the velocity and pressure fields directly from the images is challenging. We addressed this problem by developing hidden fluid mechanics (HFM), a physics-informed deep-learning framework capable of encoding the Navier-Stokes equations into the neural networks while being agnostic to the geometry or the initial and boundary conditions. We demonstrate HFM for several physical and biomedical problems by extracting quantitative information for which direct measurements may not be possible. HFM is robust to low resolution and substantial noise in the observation data, which is important for potential applications.

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Hidden fluid mechanics: Learning velocity and pressure fields from flow visualizations.

I would like to acknowledge three research grants/contracts that are supporting my current research on this theme: Grant F/07 040/AP from the Leverhulme Trust; Grant NE/F014597/1 from the Natural Environment Research Council, UK, and the REFORM collaborative project funded by the European Union Seventh Framework Programme under grant agreement 282656.

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Plants as river system engineers

Olfaction: diverse species, conserved principles.

Planar laser-induced fluorescence (PLIF) is a non-intrusive technique for measuring scalar concentrations in fluid flows. A fluorescent dye is used as a scalar proxy, and local fluorescence caused by excitation from a thin laser sheet can be related to dye concentration. This review covers quantitative PLIF in aqueous flows, with discussions of fluorescence theory, experimental methods and equipment, image processing and calibration, and applications of the technique.

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Planar laser induced fluorescence in aqueous flows

The first step in processing olfactory information, before neural filtering, is the physical capture of odor molecules from the surrounding fluid. Many animals capture odors from turbulent water currents or wind using antennae that bear chemosensory hairs. We used planar laser-induced fluorescence to reveal how lobster olfactory antennules hydrodynamically alter the spatiotemporal patterns of concentration in turbulent odor plumes. As antennules flick, water penetrates their chemosensory hair array during the fast downstroke, carrying fine-scale patterns of concentration into the receptor area. This spatial pattern, blurred by flow along the antennule during the downstroke, is retained during the slower return stroke and is not shed until the next flick.

https://science.sciencemag.org/content/sci/294/5548/1948.full.pdf

Lobster Sniffing: Antennule Design and Hydrodynamic Filtering of Information in an Odor Plume

Two techniques are described for measuring the scalar structure of turbulent flows. A planar laser-induced fluorescence technique is used to make highly resolved measurements of scalar spatial structure, and a single-point laser-induced fluorescence probe is used to make highly resolved measurements of scalar temporal structure. The techniques are used to measure the spatial and temporal structure of an odor plume released from a low-momentum, bed-level source in a turbulent boundary layer. For the experimental setup used in this study, a spatial resolution of 150 μm and a temporal resolution of 1,000 Hz are obtained. The results show a wide range of turbulent structures in rich detail; the nature of the structure varies significantly in different regions of the plume.

High-resolution measurements of the spatial and temporal scalar structure of a turbulent plume

https://web.williams.edu/Mathematics/sjmiller/public_html/105Sp10/addcomments/MooreCrimaldi_OdorLandscapesAnimalBehavior.pdf

Odor landscapes and animal behavior: tracking odor plumes in different physical worlds

We describe a laboratory investigation into the effect of turbulent hydrodynamic stresses on clam larvae in the settlement phase of the recruitment process. A two-component laser-Doppler anemometer (LDA) was used to measure time histories of the instantaneous turbulence structure at potential recruitment sites within reconstructed beds of the adult Asian clam, Potamocorbula amurensis.Measurements were made for two flow speeds over beds with three different clam densities and two different clam heights. We analyze the statistical effect of the turbulence on the larval flux to the bed and on the probability of successful anchoring to the substrate. It is shown that the anchoring probability depends on the nature of the instantaneous stress events rather than on mean stresses. The instantaneous turbulence structure near the bed is altered by the flow rate and the spacing and height of adult clams living in the substrate. The ability to anchor quickly is therefore extremely important, since the time sequence of episodic turbulent stress events influences larval settlement success. The probability of successful larval settlement is predicted to decrease as the spacing between adults decreases, implying that the hydrodynamics impose negative feedback on clam bed aggregation dynamics. Species success, population density, and community structure are all dependent on larval recruitment. Therefore, the processes of settlement and recruitment of benthic and epibenthic communities have been the subject of substantial research (see Olafsson et al. 1994; Wildish and Kristmanson 1997 for recent reviews). A major portion of the work has involved the transport of larvae to the bed and settling of the larvae by passive or active selection processes ( see reviews by Butman 1987; Abelson and Denny 1997). Several researchers have found that it is the combination of larval behavior (e.g., swimming, crawling, burrowing) and physical processes that deliver the larvae to the bed that is responsible for the recruitment success (Mullineaux and Butman 1990; Butman and Grassle 1992; Grassle et al. 1992; Snelgrove et al. 1993). As summarized by Underwood and Keough (2001), it is no longer a question of whether hydrodynamics or behavior are important in recruitment, rather it is a question of ‘‘under which conditions is larval behavior important?’’ We will expand this question and say that it is also important to determine the periods, during the relevant physical processes, when larval behavior is important. Related to the interest in larval recruitment is an ecological interest in what regulates temporal, spatial, and agesegregated distributions of species. Thus, the processes important in determining how aggregations of benthic 1

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John P. Crimaldi

Papers

Planar laser induced fluorescence in aqueous flows

Lobster Sniffing: Antennule Design and Hydrodynamic Filtering of Information in an Odor Plume

High-resolution measurements of the spatial and temporal scalar structure of a turbulent plume

Odor landscapes and animal behavior: tracking odor plumes in different physical worlds

Hydrodynamics of larval settlement: The influence of turbulent stress events at potential recruitment sites