Tissue-Specific Trade-Offs Between Biomineralisation and Antioxidant Responses in Magallana gigas Infected with Boring Sponges Pione vastifica

Infestation by boring sponges poses a serious problem for Pacific oyster Magallana gigas (Thunberg, 1793) aquaculture. This study aimed to assess the effect of Pione vastifica sponge infestation on the oysters’ capacity for shell repair, antioxidant defence status, and hemocyte functional state. We analysed the expression of VEGF pathway genes and biomineralisation enzymes, molecular chaperones (Hsp70, Hsp90), growth arrest and DNA damage gene (Gadd45α), antioxidant enzyme activity and lipid peroxidation levels in the hemolymph and various mantle parts (central and outer-edge). Intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential in hemocytes were evaluated. The results showed that infection significantly increases intracellular ROS levels in hemocytes without changing mitochondrial membrane potential. Oxidative damage was localised primarily in the central mantle contacting the damaged shell. In the outer-edge mantle responsible for shell growth, marked upregulation of SodMn, Cat, and Gadd45α was observed, coupled with suppression of VEGF-R receptor expression and organic matrix genes. Heat shock protein expression decreased in all examined tissues of infected molluscs. Our results demonstrate that shell damage induced by boring sponges triggers a tissue-specific reorganisation of physiological priorities, manifesting as a bioenergetic trade-off where limited energy resources are reallocated from the ATP-demanding process of biomineralisation to sustain antioxidant defence and cell survival.