The influence of the high content of Cа2+, Mg2+ and Na + on variability of the pores number in lateral line cranial canals of roach fingerlings

In a five-month aquarium experiment, roach Rutilus rutilus (Linnaeus, 1758) fingerlings were grown under different hydrochemical conditions. Roach eggs were collected during the spawning period in the shallow coastal waters of a small isolated and unpolluted pond and placed in laboratory for subsequent incubation. Hatched early larvae after switching to exogenous nutrition were divided into four groups for further development in control hydrochemical condition and in the water with a total mineralization increased twice relative to the control due to the addition of calcium, magnesium or sodium chloride salts. At the end of the experiment, roach fingerlings grown in the three groups in conditions of increased water mineralization differed statistically significantly from their coevals in the control group by a smaller average number of pores in the lateral line canals located on some paired dermal bones of the head. Also, these three groups of roach in comparison with the control group were characterized by an increase in the dispersion of the fluctuating asymmetry of the total values of the studied bilateral counting features. The obtained results are explained in the light of the possible influence of the above biologically significant cations on the morphogenesis of the cranial seismosensory system during the early individual development of fishes.