Stress susceptibility of echinoderms reared under aquaculture conditions

Sea urchins and sea cucumbers are becoming increasingly important sources of food and marine pharmaceuticals. Sea urchin roe has been considered a delicacy for many years, and the demand for it has been increasing. Sea cucumbers are a valuable resource both for food and the production of nutraceuticals and pharmaceuticals. Though there have been many fisheries established to harvest sea urchins, many of them have been greatly depleted, or yield poor quality roe. Since the sea cucumber is such a valuable product, the market for the giant California sea cucumber, Parastichopus californicus , has greatly increased, which has caused the establishment of fisheries along the west coast of North America. However, because the sea cucumber industry is poorly regulated, the fisheries are not believed to be sustainable, and there is interest in promoting the aquaculture of this species. In order to alleviate these problems, both for sea urchins and sea cucumbers, intensive aquaculture is generating interest as a solution. However, when an animal is placed into an artificial system, there are a variety of stresses that it can encounter, such as salinity changes or handling. In addition, sea urchins are a primary research model for embryological and developmental research, and sea cucumbers are being used in research as sources of marine based medicines, both of which necessitates the handling of the adult animals, which can cause stress. Since aquaculture conditions can cause stress to animals, which makes them more susceptible to disease, it is important to determine the stress susceptibility of sea urchins and sea cucumber to two potential stresses, handling and low salinity. In order to study the impact of these stressors, a variety of physiological and immunological assays were done on the coelomic fluid of purple sea urchins, Strongylocentrotus purpuratus and giant California sea cucumbers. Assays included total and differential cell counts, packed cell volume, coelomic fluid protein, phagocytic capacity, lytic activity, and respiratory burst activity. These assays were chosen as there tend to be clear changes in individuals that experience stress as compared to unstressed individuals. Our results indicated that low salinity and handling both cause significant stress responses in both physiological and immunological parameters in sea urchins relative to controls. For sea cucumbers, there were few significant differences from the control, and no differences in parameters analyzing immune function. These results indicate that the giant California sea cucumber is more likely to be productive in an aquaculture environment than the purple sea urchin, and that facilities interested in raising sea urchins should be particularly careful to avoid any condition that is potentially stressful