Seasonal changes in adenylate energy metabolism in the muscle and liver of the redear sunfish, Lepomis microlophus

Abstract

Levels of muscle and liver adenylates, phosphocreatine (PCr), totaladenylates (TA) and the adenylate energy charge (AEC) exhibitedsignificant seasonal changes. Fish size and condition factors weresignificantly different throughout this study; however there were nocorrelations between fish size or condition factor and metabolitelevels. Muscle adenosine triphosphate (ATP), TA and AEC were lowest inwinter and positively correlated with temperature; while adenosinediphosphate (ADP) and adenosine monophosphate (AMP) levels were high inwinter and negatively correlated with temperature. Muscle AEC's droppedinto the stressed range (0.5- 0.75) during winter months. ATP/ADP ratioswere lowest while PCr/ATP ratios were highest in winter months;indicating that a capacity for phosphate buffering existed and could notaccount for these low muscle AEC's. Liver ATP, TA, PCr, AEC, andadenylate ratios were lowest in the spring and were not correlated withtemperature, but rather coincided with reproduction. Liver AEC's droppedinto the lethal range (< 0.5) in April; although no fish mortalitieswere observed. Liver AEC's were lower than muscle AEC's throughout thestudy. The AEC appears to have some validity as a long-term indicator ofphysiological status and may have application in monitoring/predictiveprograms due to its predictable response to seasonal change. However,cautious use is suggested until temperature effects on adenylatemetabolism and seasonal effects on metabolic recovery following capturestress can be established.