Toward reference intervals for shellfish: An illustrative case of feeding and respiratory activities in the Pacific cupped oyster, Crassostrea gigas

Abstract

Background: The Quality Assurance and Laboratory Standards Committee of the American Society for Veterinary Clinical Pathology and the guidelines of the Clinical and Laboratory Standards Institute provide a framework for establishing reference intervals of physiological parameters in reputedly healthy individuals, humans, and terrestrial animals, respectively. This framework was applied for the first time to the Pacific cupped oyster, Crassostrea gigas. Reference intervals (RIs) would, first, be of interest for research purposes, including pathophysiology studies. RI determination is the first step before considering the use of RIs for field applications by farmers and marine shellfish health services. Objectives: The purpose of this study was to propose reference intervals of feeding and respiration parameters, the clearance rate (CR), and oxygen consumption rate (OCR), in a reference population of hatchery-reared diploid Pacific oysters. Methods: A de novo, a priori, and a direct approach were applied. The reference values acquired from 214 healthy diploid C gigas (total wet weight 6.23-83.64 g, DW 0.06-1.87 g) were analyzed using a non-parametric statistical method. Results: Reference intervals were proposed for CR, 0.7-4.1 L/h/g dry flesh weight (DW), and OCR, 0.4-1.3 mg O2/h/g DW in C gigas in a seawater at a temperature of 22℃ and a salinity of 32‰. Animals were fed 30-40 cells/µL of Isochrysis affinis galbana. The confidence intervals at 90% of the upper limits of the two parameters were found to be higher than those of the Clinical and Laboratory Standards Institute (CLSI) recommendations. Conclusions: Obtaining reference intervals is an important step and must be completed by proposed decision limits to facilitate the early detection of health disorders in C gigas.

Physiological comparisons of Pacific cupped oysters at different levels of ploidy and selection to OsHV-1 tolerance

“…The physiological measures were performed in the Ifremer laboratory at La Tremblade which is equipped with apparatus allowing the individual and simultaneous acquisition of clearance rate (CR, l h -1 ) and oxygen consumption (OCR, mg h -1 ) of marine bivalves (Haure et al, 2003). The set-up consists of sixteen chambers each having a volume of 2 liters and supplied continuously (Figure 1) (François et al, 2020). The treated seawater (filtration at 1 µm and sterilization by UV) and the phytoplankton Isochrysis affinis galbana (clone T-Iso) were mixed in a tank (1), then distributed by pump (2) to fifteen chambers (3), each containing a single oyster, plus a control chamber without oysters (4).…”

“…The comparison of our observations with those of previous studies is not easy and comes up against the considerable variability of the results, probably due to the different procedural modes implemented. A recent study performed on the determination of reference CR and OCR values for C. gigas pointed to the difficulty of comparing different studies with each other when the experimental conditions are not standardized (François et al, 2020). The authors recommended that researchers should work with a homogenous population of oysters, provide a supply of microalgae of constant quality and quantity, and have good control over experimental conditions (especially temperature, salinity and flowrate).…”