Serendipity and Sea Urchins.

Among the myriad of organisms that have been studied by biologists over the past 125 years, echinoderms, in particular, have been featured prominently in The Biological Bulletin throughout its history, going back to its immediate journal predecessor, the Zoölogical Bulletin (Andrews, 1898. Zool. Bull. 2: 1–13). There have been many studies published in the Bulletin on echinoderm embryology, developmental biology, behavior, natural history, morphology, and physiology. These pentaradial wonders have been useful for studying basic biology and more recently in understanding effects of climate change and ocean acidification on organisms (Matson et al., 2012. Biol. Bull. 223: 312–327; Dubois, 2014. Biol. Bull. 226: 223–236). My own brush with echinoderms was no accident, but some of the findings were a surprise (Burnett et al., 2002. Biol. Bull. 203: 42–50). On an excursion to one of my favorite research spots, the Oregon Institute of Marine Biology, in Charleston, Oregon, I was working with my longtime friend and colleague Nora Terwilliger and a few of my other favorite colleagues. We were there to examine the physiological responses of some of the local organisms when exposed to the air at low tide, an interest of mine. We had picked the purple sea urchin and a large barnacle as test organisms. They were good candidates because we could easily sample fluid from their body cavities. The sea urchins were especially easy to sample. And we would measure things that any respiratory and acid-base physiologist would measure. Early in our study, serendipity paid us a visit. I remember David Scholnick, one in our group, walking into the lab, holding a sea urchin, and proclaiming that sea urchins leak water from somewhere for minutes after they are exposed to air. We knew how to sample the fluid, called perivisceral coelomic fluid (PCF), from the main body compartment; and this allowed us to make our measurements. But now we had to figure out what was going on with this substantial volume of fluid, which we called “emersion fluid,” that was