Abstract
The pearl oyster is one of the rare animal models that support two distinct genomes, through the surgical graft process operated for culture pearl production. This grafted organism is assimilated to a chimera whose physiological functioning remains poorly known. The question of the energy expenditure comparison between chimera and non-chimera animals arises. To answer this question, grafted and non-grafted pearl oysters were evaluated for their energetic needs by the indirect calorimetry method. This method made it possible to measure the energy expenditure based on the respiration rate (RR) measurement, reflecting the basal metabolism. The results showed that the RR values for grafted and non-grafted pearl oysters were not significantly different (p < 0.05). The estimated cost of pearl calcification including CaCO3 and proteins synthesis was 0.237 ± 0.064 J h−1, representing 0.64% of the total energy expenditure of grafted pearl oysters. This study made it possible, for the first time, to see the energy cost of cultured pearl formation in P. margaritifera and the little impact in the energetic metabolism of the chimera organism.
Highlights
The grafting process during cultured pearl formation creates a unique organism, a chimera from a genetic point of view, that consists of genetic material delivered by two distinct genomes: the graft of the donor into the gonad called pearl pouch of a recipient oyster[1,2,3]
For cultured pearl formation, energy of the recipient pearl oysters is potentially allocated to the functioning of the pearl sac epithelial cells
These cells were first known to be implicated in the molecular expression of the matrix protein synthesis, which is involved in nacre production[6,18,19]
Summary
The grafting process during cultured pearl formation creates a unique organism, a chimera from a genetic point of view, that consists of genetic material delivered by two distinct genomes: the graft of the donor into the gonad called pearl pouch of a recipient oyster[1,2,3]. Its rate has recently been estimated in P. margaritifera in six grow-out locations in French Polynesia and ranges between 0.051 and 0.064 g per month[7], which corresponds to an average daily nacre deposition thickness of approximately 3.4 μm per day[8] This growth requires a constant energy supply during cultured pearl formation. The energy expenditure was assessed using an indirect calorimetry method based on the measurement of the respiration rate of starved pearl oysters, reflecting the standard metabolic rate taking into account the condition index as indicator for maintenance and sexual activity of molluscs[17]
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