Stephen Williams
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January 2025 · Poster

MDDLS 2025: Exploring Thermally Stressed Symbiosis Formation

A poster at UC Irvine on how heat stress may disrupt the flows young bobtail squid use to recruit their symbionts.

Squid project

At the Mathematics of Data, Dynamics, and Life Sciences meeting at UC Irvine in January 2025, I presented a poster on modeling symbiosis establishment in juvenile Euprymna scolopes.

Authors: Stephen Williams, Kyra Ruiz, Elizabeth Heath-Heckman, Erica Rutter, Shilpa Khatri

Abstract

Symbioses underpin the survival of many organisms, but rapid environmental change may expose hidden vulnerabilities in these partnerships. The bobtail squid and its bacterial partner Vibrio fischeri are a model system for studying how flows created by the ciliated structures of the light organ recruit bacteria. We simulate bacterial motion in these flows and examine how climate-driven changes could affect colonization.

Summary

Juvenile squid acquire their symbionts from seawater by breathing, and cilia on the light organ’s appendages capture the bacteria. We modeled these flows with the method of regularized Stokeslets [9, 10], varying breathing strength, breathing frequency, ciliary beating and squid size, and measured how long bacteria stay near the light organ.

A Sobol sensitivity analysis [8, 11] across 81,920 simulations showed that breathing frequency has the strongest individual effect. Faster, harder breathing, as seen under thermal stress, shortens how long bacteria stay near the light organ, suggesting heat stress could hinder colonization.

This work became our paper on thermal stress and symbiotic fluid dynamics.

References

  1. Journal of Theoretical Biology (1967). Link
  2. Nawroth, J. C. et al. Motile cilia create fluid-mechanical microhabitats for the active recruitment of the host microbiome. PNAS (2017). doi:10.1073/pnas.1706926114
  3. Effects of activity, temperature and mass on the respiratory metabolism of the squid Illex illecebrosus. Journal of the Marine Biological Association of the UK. Link
  4. Journal of Comparative Physiology B (2006). doi:10.1007/s00360-006-0084-9
  5. The Biological Bulletin. doi:10.2307/1543086
  6. Kim, S., Karrila, S. J. Microhydrodynamics: Principles and Selected Applications. Butterworth-Heinemann. Link
  7. Frontiers in Cell and Developmental Biology (2022). doi:10.3389/fcell.2022.974213
  8. ZAMM: Journal of Applied Mathematics and Mechanics (1997). Link
  9. Cortez, R. The method of regularized Stokeslets. SIAM Journal on Scientific Computing (2001). doi:10.1137/S106482750038146X
  10. Cortez, R., Fauci, L., Medovikov, A. The method of regularized Stokeslets in three dimensions. Physics of Fluids 17, 031504 (2005). Link
  11. Saltelli, A. et al. Variance based sensitivity analysis of model output. Design and estimator for the total sensitivity index. Computer Physics Communications (2010). Link