THE VISUAL DESIRABILITY OF THE PACIFIC OYSTER Magallana gigas : IMPACT OF METABOLOME AND ‘CURING’ LOCATION
Aquaculture of oysters is expected to grow from $9 billion to $11 billion by the end of the decade. Desirability of stock oysters drives lease and grow out placement , with three sensory attributes that contribute to an oyster’s desirability: visual, smell, and taste (i.e., the meroir, or ’taste of the ocean’). It may be possible to influence these factors simply by moving the ’curing’ site to a location with more favourable environmental parameters (i.e., higher salinity, regulated temperature, specific food species). Its visual appeal changes drastically with location, which directly impacts oyster molecular mechanisms and desirable phenotypes.
This study looked at the effects of sites and legacy signals on the metabolome of oysters, which is important for oyster aquaculture. Through this study, metabolites contributing to specific visual characteristics will be identified, allowing industry to select optimal ‘curing’ sites that are conducive to these metabolic pathways and desirable oyster phenotypes.
To meet this need, oysters were translocated from two leases , Smithton (NW coast) and Boomer Bay (SE coast), to a ‘curing’ site, Pitt Water, chosen by Tasmania Oyster Co. This move is commonly done to improve the quality of oysters in Tasmania. Individuals (n=20) were randomly selected for analysis, two weeks and four weeks post trans-location. Water samples and environmental parameters were taken at each sampling point in parallel to oyster samples. Selected oysters were photographed and blindly assessed and graded on their mantle, body and shell fullness. Oysters were dissected targeting the mantle, gill, palp and digestive gland. Tissues were analysed for central carbon metabolism (CCM) metabolites using a liquid chromatography mass spectrometry (LC-TQ) targeted metabolomics methodology.
Results indicated the up regulation of 4-Methyl-2-oxovaleric acid in the mantle tissue between high and low-grade oysters with the down regulation of Xanthine and Gly oxylic acid. In contrast, the digestive gland showed significant up regulation of Cytidine 5-Diphosphates, Vanillic acids and Uridine 5-Monophosphate and down regulation of 2-Deoxyadenosine , 2-Deoxyuridines and L-Sorboses. More generally, there was significant up regulation in 25 metabolites between tissues with significant down regulation found in 52 .
Understanding the metabolome of oysters is important when determining causes of visual desirability metrics. Changes in the metabolome and microbiome have a direct association with the visual desirability of oysters and can be manipulated by the source oyster’s ‘curing’ location .