Intermediary metabolism in mudskippers,Periophthalmodon schlosseriandBoleophthalmus boddarti, during immersion or emersion

Abstract

This study aimed to examine effects of 48 h emersion on intermediary metabolism in the mudskippers Periophthalmodon schlosseri (Pallas, 1770) and Boleophthalmus boddarti (Pallas, 1770). The glycogen content increased significantly, while the lactate content remained unchanged, in the muscle of P. schlosseri during 48 h of emersion. Thus, emersion led to either a decrease in glycogen utilization or an increase in glycogen synthesis. Because there was no change in energy charge, P. schlosseri probably used energy stores other than glycogen during emersion. The phosphofructose kinase-1 (PFK) from the muscle of P. schlosseri became more sensitive to ATP inhibition after 6 h of emersion, indicating that a transient decrease in the glycolytic flux indeed occurred at this locus that led to an increase in glycogen content. In contrast, such phenomena were not observed in the muscle of B. boddarti during 48 h of emersion. Emersion also led to a significant increase in the muscle fructose-2,6-bisphosphate (F26P2) content in P. schlosseri, but not in B. boddarti. Based on results obtained from P. schlosseri undergoing forced exercise, we propose that a correlation may exist between the F26P2content and the utilization of amino acids as an energy source in this mudskipper during emersion.