| Summary: | The Pacific sand dollar, Dendraster Excentricus, belongs to a broad category of marine ectotherms whose growth and development are influenced by various environmental parameters, including temperature, food availability, and ocean acidification [1]. These environmental factors impact the morphology of the organism. Additionally, existing literature suggests functional tradeoffs are associated with morphological parameters, particularly arm length [2]. These tradeoffs have implications for both larval development and the remaining remainder of the organism's life cycle. Our overarching thesis is that characterizing the hydrodynamics of marine larvae (in this investigation, sand dollar larvae) could serve as metrics to carefully quantify these tradeoffs and understand the functional consequences of morphology and adaptations. Since larval swimming and feeding structures (ciliated arms) also respond to dynamic environment cues (for example, flow), approaches are needed that introduce well-controlled environmental factors. These tasks are accomplished by integrating fluorescent microscopy and microfluidics to create a miniaturized particle image velocimetry (mPIV) system to examine underlying hydrodynamics and material transport of sand dollar larvae. Improving upon current hydrodynamic investigations of ciliary swimming, this method focuses on metrics of swimming performance with an emphasis on the material transport of oxygen, an essential molecule in metabolism. Microfluidics enabled examining a campaign of low-fed (LF) larvae from multiple days post fertilization (DPF). Dimensionless analysis using the Peclet and Reynolds number suggested that ciliary activities enable the larvae to create local velocities that help them capture food and overcome oxygen diffusion in a viscosity-dominated environment.
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