The Whole Is Greater Than The Sum of Its Parts: Large-scale Phenomena Arising from Small-Scale Biophysical Processes.

The symposium "Large-scale biological phenomena arising from small-scale biophysical processes" at the SICB 2023 Annual General Meeting focused on the cross-disciplinary exploration of emergent phenomena in biology. Interactions between cells or organisms at small scales within a system can govern patterns occurring at larger scales in space, time, or biological complexity. This theme recurs in many sub-disciplines of biology, including cell and developmental biology, evolution, and ecology. This symposium, and the associated special issue introduced here, showcases a wide range of cross-disciplinary collaborations among biologists, physicists, and engineers. Technological advancements in microscopy and microfluidics, as well as complementary advances in mathematical modelling and associated theory demonstrate the timeliness of this issue. This introduction seeks to provide useful background information to place the studies within this issue in a broader biophysical context and highlight similarities in ideas and approaches across systems and sub-disciplines. We hope to demonstrate that cross-disciplinary research linking small-scale biophysics to larger-scale emergent phenomena can help us understand problems ranging from single-cell behaviors to tissue formation and function, evolution of form, and the dynamics of communities.

Common Interests Without Common Expertise: Reflections on Early-career Experiences in Cross-Disciplinary Research.

Cross-disciplinary research enables us to tackle complex problems that require expertise from different fields. Such collaborations involve researchers who have different perspectives, communication styles, and knowledge bases, and can produce results far greater than the sum of their parts. However, in an era of increasing scientific specialization, there exist many barriers for students and early-career researchers (ECRs) interested in training and undertaking interdisciplinary research endeavors. This perspective examines the challenges that students and ECRs perceive and experience in cross-disciplinary work and proposes pathways to create more inclusive and welcoming research environments. This work emerges from a National Science Foundation (NSF)-funded workshop held during the Society for Integrative and Comparative Biology (SICB) Annual Meeting in January 2023 in Austin, TX. The workshop brought together seasoned interdisciplinary scientists with undergraduate and graduate students to identify and discuss perceived challenges through small group discussions and experience sharing. Through summarizing a range of student concerns about embarking on careers as interdisciplinary scientists and identifying ways to dismantle institutional and lab management-level barriers, we aim to promote an inclusive and collaborative problem-solving environment for scientists of all experience levels.

ARC: An Open Web-Platform for Request/Supply Matching for a Prioritized and Controlled COVID-19 Response.

In 2020 the world was hit by the COVID-19 pandemic putting entire governments and civil societies in crisis mode. Around the globe unprecedented shortages of equipment and qualified personnel were reported in hospitals and diagnostic laboratories. When a crisis is global, supply chains are strained worldwide and external help may not be readily available. In Switzerland, as part of the efforts of the Swiss National COVID-19 Science Task Force, we developed a tailor-made web-based tool where needs and offers for critical laboratory equipment and expertise can be brought together, coordinated, prioritized, and validated. This Academic Resources for COVID-19 (ARC) Platform presents the specialized needs of diagnostic laboratories to academic research groups at universities, allowing the sourcing of said needs from unconventional supply channels, while keeping the entities tasked with coordination of the crisis response in control of each part of the process. An instance of the ARC Platform is operated in Switzerland (arc.epfl.ch) catering to the diagnostic efforts in Switzerland and sourcing from the Swiss academic sector. The underlying technology has been released as open source so that others can adopt the customizable web-platform for need/supply match-making in their own relief efforts, during the COVID-19 pandemic or any future disaster.

Departures from isotropy: the kinematics of a larval snail in response to food.

The swimming behavior of invertebrate larvae can affect their dispersal, survival and settlement in the ocean. Modeling this behavior accurately poses unique challenges as behavior is controlled by both physiology and environmental cues. Some larvae use cilia to both swim and create feeding currents, resulting in potential trade-offs between the two functions. Food availability is naturally patchy and often occurs in shallow horizontal layers in the ocean. Also, larval swimming motions generally differ in the horizontal and vertical directions. In order to investigate behavioral response to food by ciliated larvae, we measured their behavioral anisotropy by quantifying deviations from a model based on isotropic diffusion. We hypothesized that larvae would increase horizontal swimming and decrease vertical swimming after encountering food, which could lead to aggregation at food layers. We considered Crepidula fornicata larvae, which are specifically of interest as they exhibit unsteady and variable swimming behaviors that are difficult to categorize. We tracked the larvae in still water with and without food, with a portion of the larvae starved beforehand. On average, larvae in the presence of food were observed higher in the water column, with higher swimming speeds and higher horizontal swimming velocities when compared with larvae without food. Starved larvae also exhibited higher vertical velocities in food, suggesting no aggregation behavior. Although most treatments showed strong anisotropy in larval behavior, we found that starved larvae without food exhibited approximately isotropic kinematics, indicating that behavioral anisotropy can vary with environmental history and conditions to enhance foraging success or mitigate food-poor environments.

Not Just Going with the Flow: The Effects of Fluid Flow on Bacteria and Plankton.

Microorganisms often live in habitats characterized by fluid flow, from lakes and oceans to soil and the human body. Bacteria and plankton experience a broad range of flows, from the chaotic motion characteristic of turbulence to smooth flows at boundaries and in confined environments. Flow creates forces and torques that affect the movement, behavior, and spatial distribution of microorganisms and shapes the chemical landscape on which they rely for nutrient acquisition and communication. Methodological advances and closer interactions between physicists and biologists have begun to reveal the importance of flow-microorganism interactions and the adaptations of microorganisms to flow. Here we review selected examples of such interactions from bacteria, phytoplankton, larvae, and zooplankton. We hope that this article will serve as a blueprint for a more in-depth consideration of the effects of flow in the biology of microorganisms and that this discussion will stimulate further multidisciplinary effort in understanding this important component of microorganism habitats.

Ontogenetic changes in larval swimming and orientation of pre-competent sea urchin Arbacia punctulata in turbulence.

Many marine organisms have complex life histories, having sessile adults and relying on the planktonic larvae for dispersal. Larvae swim and disperse in a complex fluid environment and the effect of ambient flow on larval behavior could in turn impact their survival and transport. However, to date, most studies on larvae-flow interactions have focused on competent larvae near settlement. We examined the importance of flow on early larval stages by studying how local flow and ontogeny influence swimming behavior in pre-competent larval sea urchins, Arbacia punctulata We exposed larval urchins to grid-stirred turbulence and recorded their behavior at two stages (4- and 6-armed plutei) in three turbulence regimes. Using particle image velocimetry to quantify and subtract local flow, we tested the hypothesis that larvae respond to turbulence by increasing swimming speed, and that the increase varies with ontogeny. Swimming speed increased with turbulence for both 4- and 6-armed larvae, but their responses differed in terms of vertical swimming velocity. 4-Armed larvae swam most strongly upward in the unforced flow regime, while 6-armed larvae swam most strongly upward in weakly forced flow. Increased turbulence intensity also decreased the relative time that larvae spent in their typical upright orientation. 6-Armed larvae were tilted more frequently in turbulence compared with 4-armed larvae. This observation suggests that as larvae increase in size and add pairs of arms, they are more likely to be passively re-oriented by moving water, rather than being stabilized (by mechanisms associated with increased mass), potentially leading to differential transport. The positive relationship between swimming speed and larval orientation angle suggests that there was also an active response to tilting in turbulence. Our results highlight the importance of turbulence to planktonic larvae, not just during settlement but also in earlier stages through morphology-flow interactions.