DEVELOPMENTAL STABILITY IN PERCH (PERCA-FLUVIATILIS) IN ACIDIC ALUMINUM-RICH LAKES

Fluctuating asymmetry is defined as random deviation from perfect bila teral symmetry resulting from environmental or genetic disturbances (t ermed developmental noise) during early embryonic development. Develop mental instability is defined as the inability of an organism to follo w the a priori defined growth trajectory that results in perfect bilat eral symmetry, owing to insufficient buffering of the disruptive effec ts of developmental noise during development. Fluctuating asymmetry ha s been proposed for use as a measure of developmental instability. In this study we tested whether fluctuating asymmetry can be an early ind ication of acidification stress. Samples were taken from 10 perch (Per ca fluviatilis) populations exposed to varying pH levels and aluminium concentrations. We scored 13 bilateral meristic and morphometric char acters to assess fluctuating asymmetry. The level of fluctuating asymm etry in the mandibular pores and one index summarizing three of the me ristic characters were significantly correlated with the acidification level. When the lakes were split into two groups, ''acidified'' and ' 'control,'' each consisting of five lakes, the same pattern emerged. T he variance of fluctuating asymmetry estimates was larger in the acidi fied lakes than in the control lakes. These findings imply that perch in acidic environments experience developmental perturbations during e arly embryogenesis, resulting in deviating bilateral morphology. The v ariation in fluctuating asymmetry among lakes was at the same level as previously found among age groups within one acidified lake. Based on these findings, the use of fluctuating asymmetry as a management tool to evaluate the viability of fish populations in acidified waters is of limited value unless a more comprehensive approach is used.