RESUMO
This study presents data collected over a 6 year period on the effects of extremely low-frequency magnetic fields (MFs) (1.4-1.6 µT, 500 Hz and 1.4-1.6 µT, 72.5 Hz) and MFs in combination with other environmental stressors (elevated temperature, 0.01 mg l(-1) trichlorfon, 0.01 mg l(-1) copper sulphate pentahydrate) on roach Rutilus rutilus embryos. Effects were studied during different stages of early development. Rutilus rutilus were raised in ponds for 4 months after exposure to MFs. The mass, standard length (LS ) and morphological characteristics of underyearlings which were exposed as embryos were recorded. An increase in embryo mortality and a decrease in LS and mass indices in underyearlings were noted after they had been exposed to a combination of MFs and different adverse environmental factors. In addition, exposure to MFs led to changes in the total number of vertebrae and the number of seismosensory system openings in the mandibular bones of underyearlings. MFs of different frequency caused both increases (500 Hz) and decreases (72.5 Hz) in morphological diversity. The stressors used in this study, however, did not increase the fluctuating asymmetry of bilateral morphological characteristics. The possible microevolutionary effects of exposure to MFs alone and in combination with other adverse environmental factors upon natural fish populations are discussed.