Publication Abstract

Pacific oysters (Magallana gigas, Thunberg 1793) preferentially consume Isochrysis galbana, increasing biomass and an upregulating biomineralisation gene nacrein

Microalgae are the foundation of oyster diets in aquaculture. And as demand for oysters increases, so does the need for nutritionally complete diets. Isochrysis galbana is considered optimal oyster diet and is often supplemented with other algae like Nannochloropsis to provide complementary nutrients, but which diet do the oysters prefer and what effects do the diets have on physiology? This study performed feeding experiments with single (I. galbana or Nannochloropsis) and mixed (both species combined) diets in Pacific oysters (Magallana gigas). Oysters fed exclusively I. galbana had greater biomass gains but reduced shell growth, indicated by a lower Oyster Condition Index, and gene expression analysis showed compensatory upregulation of biomineralisation gene nacrein in this group. Oysters fed mixed diets showed higher algal cell clearance and pseudofaeces production, and within the mixed diet, a preference for I. galbana. This suggests that while a mixed-algae diet is traditionally used, a single species diet of I. galbana can significantly enhance oyster growth, reducing the need for complex multi-species algal culture. Culturing one alga is more time- and cost-effective, and stage-specific diets could promote specific physiological factors: reduced I. galbana in early stages so that protective shell growth is prioritised, then increased I. galbana later to enhance tissue growth. These findings can help to optimise oyster feeding in a world with increasing demand for oysters.

 

Amy Lovegrove*, Sargent Bray, Gordon Inglis, Megan Wilding, Bastian Hambach, Thomas Bibby, Christopher Hauton

 

Journal of Experimental Marine Biology and Ecology