Dataset: Initial (Ti) and final (Tf) microsphere counts from Dendraster excentricus feeding incubations with microspheres differing in size or functionalized surface

Larval cultures were reared and experimental incubations carried out at the Oregon Institute of Marine Biology from March to April 2025. Experimental feeding incubations using artificial microspheres and natural prey were carried out on 5-day old D. excentricus plutei. Prior to incubations, larvae were removed from their culture container and picked into a small volume (~100 milliliters (mL)) of filtered (0.22 µm) seawater (FSW) using a pulled and flamed Pasteur pipette. After starving briefly (up to 1 hour), 10 larvae were picked into 10-mL glass incubation vials with experimental prey field and allowed to feed for up to 1 hour. We carried out several incubations to investigate selectivity based on prey size and surface. To investigate differential ingestion based on prey size, we used 0.5, 1.0, 3.0, and 10 micrometer (µm) polystyrene microspheres with carboxylate-modified surface and yellow-green (YG) fluorescence (see Table 1 under Supplemental Files). Following the results of prey size, we compared 1.0 µm particles with different surface properties, including polystyrene and silica as well as two different functionalized surfaces; those modified with carboxylate groups or amine groups (Table 1).

Each comparison described above included 3 to 4 replicates with 8 to 10 larvae in each. Incubation chambers were manually inverted to mix every 10 minutes. This concentration of approximately 1 larva per mL incubation is below the known clearance rate of D. excentricus larvae at this age (<1 mL per hour for 10 larvae, Hart 1996). Following incubations, larvae were removed individually by pipetting from incubation chambers, suspended in 1 mL FSW, and similarly fixed in 0.125% glutaraldehyde. All samples were stored in the dark at 4 degrees Celsius (˚C) prior to analysis.