Variability in development of bilateral parts of the brain during ontogenesis of roach (Rutilus rutilus)

A study exploiting the gravimetric method did not reveal identical development of paired parts of the roach (Rutilus rutilus) brain. In the studied sample, the proportion of fish with left or right asymmetry of this organ was 1: 1. The specificity of fluctuating asymmetry in studied plastic parameter depending on the fish age and growth was analyzed. In the ontogenetic sequence, from yearlings to nine-year-old fishes, the higher level of developmental instability was revealed in elder fish, six and more years old. Noted anatomical-morphological feature is likely determined by not only imperfect morphogenesis during early development: potential decrease in the threshold of noise immunity against unfavorable external and internal factors during later stages of fish development may contribute to the feature noted above. The analysis of sex-related traits revealed that in males fluctuating asymmetry of the brain bilateral parts is more pronounced.