SEASONAL FLUCTUATIONS IN BRAIN ACETYLCHOLINESTERASE ACTIVITY AND SOLUBLE-PROTEIN CONTENT IN ROACH (RUTILUS-RUTILUS L) - A FRESH-WATER FISH FROM NORTHWEST RUSSIA

Seasonal fluctuations in brain acetylcholinesterase (AChE) activity an d soluble protein (SP) content were studied over a 6-year period in ro ach (Rutilus rutilus L.) from Rybinsk Reservoir in Russia. There was a significant positive linear correlation between AChE activity and SP content in roach brain for all years (r = 0.49-0.95, p < 0.001). No co rrelations were found, however, between either parameter and sex, and adults or juveniles. Weak but significant (r = -0.02, p < 0.001) negat ive correlation was found between AChE activity and fish size. The dat a revealed two different seasonal patterns in both measures. During 19 87, 1990, 1994, and 1995, enzyme activity and SP content were higher i n summer than in winter, being associated with changes in water temper ature. However, the highest values for both parameters in these years also were reported during spawning. An atypical seasonal pattern in bo th parameters was observed during Fall 1988 to Spring 1989. In this pe riod, high values for both measures occurred during winter when water temperatures were lowest. (C) 1997 Elsevier Science Inc.