Dataset: Purple sea urchin morphometrics from Marna Laboratory Experiments at the Quadra Island Ecological Observatory (2021)

For a focal sea urchin, morphometrics included measurements of test dimensions, wet mass, dry mass, and ash mass as well as visual determinations of the sex and whether gametes were actively extruded immediately following dissection. Test dimensions were measured using digital calipers (Mitutoyo America Corporation®, Aurora IL, USA). Wet weight was measured using a calibrated digital scale (Mettler-Toledo, LLC., Columbus, OH, USA) following a 30 s drying period in a dry dissection tray (United States Plastic Corporation®, Lima, OH, USA). We estimated the amount of metabolically active biomass for an individual by calculating ash-free dry mass (AFDM) for each subject. AFDM quantifies soft tissue biomass while excluding skeletal biomass that does not contribute meaningfully to changes in DO. We calculated AFDM as the difference between dry mass and post-combustion ash mass (i.e., skeletal mass). We measured all mass metrics by weighing samples on a calibrated digital scale (Mettler-Toledo, LLC). To measure dry mass, we first cracked the test of the urchins and discarded the coelomic fluid, then dried the carcasses for 24 hours at 60 ℃ in a drying oven then weighed the dried carcasses. To measure post-combustion ash mass, we combusted these dried carcasses for six hours at 450 ℃ in a muffle furnace, then weighed the resulting ashes of each carcass.