Coelomic Fluid Analysis of Healthy Sea Stars and Those Affected by Sea Star Wasting Disease
Sea star wasting disease (SSWD) is one of the largest marine wildlife die-offs ever recorded and has killed millions of sea stars from 20 Asteroidea species between Alaska to Mexico since the summer of 2013. A sea star-associated densovirus has been associated with SSWD, but the exact disease etiology remains unknown.4 Coelomic fluid surrounds the sea star's organs, playing a role in nutrient transportation3 and innate immune function. Coelomocytes, similar to vertebrate leukocytes, provide cell-mediated immunity. Coelomic fluid macromolecules including lectins, agglutinins, perforins, complement and several cytokines provide a humoral response.1,2,5 To investigate the pathophysiology of SSWD, coelomic fluid (n = 107) from two commonly affected species, the mottled sea star (Evasterias troscheli) and the ochre sea star (Pisaster ochraceus), was sampled for electrolytes, total protein, and coelomocyte counts with establishment of baseline intervals for Pisaster ochraceus for magnesium (93.5–106.6 mg/dL), sodium (380–423 mEq/L), potassium (8.2–10.0 mEq/L), chloride (435–449 mEq/L), calcium (31.2–34.5 mg/dL), and total protein (1.6–2.1 g/dL). Although diseased sea stars (n = 63) demonstrated a wider range of all values, only chloride was significantly higher. Free and phagocytized bacteria were noted in 51.6% coelomic fluid samples from deceased sea stars and in no samples from healthy sea stars. The wider range of electrolytes, presence of bacteria within coelomic fluid and coelomocytes, and increased coelomocyte counts in sick animals suggest inflammation, bacterial infection, and impaired osmoregulation due to SSWD.
The authors would like to thank the staff at Boeing for their financial support of this project and Dr. Carolyn Cray from the University of Miami for performing the electrolyte analysis.
* Presenting author
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