Modeling Water Transport Across Spider Egg Sac Membranes
Can a porous membrane reduce water loss without blocking essential gas exchange? That question sits at the center of research exploring how organisms regulate moisture across biological surfaces. This project examined spider egg sacs as a model system to better understand how water vapor moves across porous membranes and what truly controls evaporation.
The research was presented at the Graduate Poster Exhibition during the 2025 SPARK! (Showcase of Projects, Art, Research, and Knowledge), a reimagining of Research Week that highlighted graduate research across disciplines. Developed within the Ph.D. program in Computational and Integrative Biology at Rutgers University–Camden’s Center for Computational and Integrative Biology (CCIB), the project was completed by Ravi Schwartz. The abstract below introduces his work on modeling water vapor transport across porous surfaces.
Abstract: Can Static Porous Membranes be Used for Selective Respiratory Exchange?
Controlling water transport across surfaces is essential for all living organisms. Spider egg sacs are multifunctional membranes that protect eggs and spiderlings from the external environment, but past research gives conflicting results about whether these mats of silk fibers can reduce evaporation of water. In part, this is because the diffusive resistance of any membrane cannot easily be measured independently of the system in which it is studied.
We develop a model to describe water vapor transport across porous surfaces that reveals that the diffusive resistance across the gap space underneath the membrane and the boundary layer on the outside of the membrane can play much greater roles in controlling water vapor flux compared to diffusion across the membrane itself. The model accurately predicts diffusive resistance of a variety of synthetic surfaces from empirical studies, as well as the egg sacs of Latrodectus hesperus and Argiope aurantia.
We show that typical spider egg sac membranes offer surprisingly low diffusive resistance to water because they are highly porous at microscopic scales. However, silk egg sacs still play key roles in controlling water loss by separating the diffusive resistance of the interior of the egg sacs from the outside boundary layer. Our model provides both a tool to explore diverse egg sac geometries and to facilitate comparison of diffusive resistance across membranes studied in diverse systems.
Graduate Poster Exhibition at SPARK!
The Graduate Poster Exhibition celebrates the research and creative work of the graduate community, showcasing everything from prose and code to original research and artistic expression. As part of SPARK! (Showcase of Projects, Art, Research, and Knowledge), a reimagining of Research Week, the exhibition highlights the depth, range, and impact of graduate scholarship and invites the campus community to engage with ideas taking shape across disciplines.
Bridging Disciplines: The Center for Computational and Integrative Biology
The Center for Computational and Integrative Biology (CCIB) at Rutgers–Camden combines experimental and computational methods to address complex biological questions. CCIB offers graduate programs leading to M.S. and Ph.D. degrees, emphasizing a holistic understanding of biological systems from molecular to population levels. The curriculum equips students like Basirat with the skills to conduct innovative research at the intersection of biology, chemistry, computer science, mathematics, and physics.
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