Coelomic fluid sampling is a noninvasive technique that is used to access the body fluid of sea stars for diagnostics and research. Given recent mortality events including sea star wasting disease, which has killed millions of sea stars along the Pacific coast since 2013, there is a need for validated diagnostic tests to evaluate sea star health. The objectives of this study were to establish coelomic fluid reference intervals for clinically normal ochre sea stars Pisaster ochraceus in an open system aquarium, to describe the cytologic findings, and to compare the chemistries of coelomic fluid with open system tank water. Coelomic fluid from 26 clinically normal sea stars was sampled for coelomocyte counts, cytologic evaluation, and biochemical analysis including magnesium, sodium, potassium, chloride, calcium, and total protein. The number of coelomocytes and total protein did not fit normal distribution and were excluded from analyses. Reference intervals were established for other chemistry analytes. There was no statistical difference in biochemistries between sea star coelomic fluid and water from five open system tanks, which supports previous evidence that sea stars are osmoconformers. Very low numbers of coelomocytes were observed cytologically. These results provide a useful baseline and diagnostic tool for health assessments of sea stars.
Welfare considerations and regulations for invertebrates have lagged behind those for vertebrates, despite invertebrates comprising more than 95% of earth's species. Humans interact with and use aquatic invertebrates for exhibition in zoos and aquaria, as pets, research subjects, and important food sources. Recent research has indicated that aquatic invertebrates, in particular cephalopod mollusks and decapod crustaceans, experience stress and may be able to feel pain. With this article, we present results of a survey on attitudes of aquatic animal health professionals toward aquatic invertebrate welfare and provide practical recommendations for advancing aquatic invertebrate welfare across four areas of opportunity: use of anesthesia, analgesia, and euthanasia; development of less invasive diagnostic and research sampling methods based on 3R principles; use of humane slaughter methods for aquatic invertebrates; and reducing impacts of invasive procedures in aquaculture and fisheries. We encourage consideration of these opportunities to achieve far-reaching improvements in aquatic invertebrate welfare.
Sea Star Wasting Syndrome (SSWS) is one of the largest marine wildlife die-offs ever recorded, killing millions of sea stars from more than 20 Asteroid species from Alaska to Mexico from 2013 to 2015 from yet undetermined cause(s). Coelomic fluid surrounds the sea star's organs, playing critical roles in numerous systemic processes, including nutrient transportation and immune functions. Coelomocytes, which are cellular components of coelomic fluid and considered functionally equivalent to vertebrate leukocytes, are responsible for innate cell-mediated immunity. The objectives of this study were to (1) evaluate changes in coelomic fluid chemistry, coelomocyte counts, and cytology from ochre sea stars (Pisaster ochraceus) (n = 55) with clinical signs consistent with SSWS at varying intensity (SSWS score 1: n = 4, score 2: n = 2, score 3: n = 3, score 4: n = 18, score 5: n = 26) in comparison to coelomic fluid from clinically normal sea stars (n = 26) and to (2) correlate SSWS score with cellular and biochemical analytes. SSWS-affected sea stars had wider ranges of all electrolytes, except calcium; statistically significantly higher chloride, osmolality, and total protein; lower calcium; and higher coelomocyte counts when compared to clinically normal sea stars maintained under identical environmental conditions. Free and/or phagocytized bacteria were noted in 29% (16 of 55) coelomic fluid samples from SSWS-affected sea stars but were absent in clinically normal sea stars. SSWS score correlated significantly with increasing chloride concentration, osmolality, and coelomocyte counts. These chemistry and cytological findings in coelomic fluid of SSWS-affected sea stars provide insight into the pathophysiology of SSWS as these results suggest osmo-and calcium dysregulation, coelomocyte responses, and presumptive opportunistic bacterial Wahltinez et al. Wasting Sea Star Coelomic Fluid infection in SSWS-affected sea stars. This information provides potential future research applications for the development of treatment strategies for sea stars in managed care and for understanding the complexity of various biochemical and cellular pathophysiological mechanisms involved in sea star wasting.
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