Identification of molecular stress indicators in pikeperch Sander lucioperca correlating with rising water temperatures

Water temperature is doubtlessly one of the most important factors affecting the well-being of fish. For pikeperch Sander lucioperca an ambient water temperature of >20 °C has been suggested to achieve optimal growth in aquaculture farms, although natural habitats of pikeperch seldom reach such temperatures. We used multiplex qPCR arrays to assess the impact of temperature between 15 °C and 25 °C based on the expression of 38 potential biomarker genes characterising heat shock and hypoxia response, immune activation, energy supply and development in the liver and gills of pikeperch. In addition, liquid chromatography/mass spectrometry was used to assess the individual levels of glucocorticoids. Our data revealed that pikeperch do not develop severe responses to ambient temperatures between 15 °C and 25 °C, although specific parameters indicated a phased restriction of optimal conditions, above all the heat-shock genes SERPINH1, HSP90AA1 and HSPA8b; the acute-phase genes HP, C3 and SAA; and the transcription factor-encoding gene HMX1. In contrast to these in vivo observations, a temperature rise up to 37 °C led to an acute response in WF2-Sander cells characterised by the pronounced upregulation of HSP90AA1, HSP1A1, SERPINH1, HSPB1, HSPA8b and HSPB8. This report paves the ground for future assessment studies on the imbalanced homeostasis of pikeperch by means of molecular tools.