[Show abstract][Hide abstract] ABSTRACT: Many industrial and agricultural chemicals (including heavy metals and alkylphenols) present in the environment have adverse effects on the reproductive function in fish. Three studies were conducted to assess toxicity of these chemicals towards reproduction of freshwater fish. It was shown that heavy metals added to the diets accumulate in brain tissue of carp, and this accumulation results in inhibition of the secretion of noradrenaline and stimulation of the secretion of dopamine in the hypothalamus. These processes results in a disturbance of hormonal equilibrium of the hypothalamo-pituitary system, which can unfavorably influence the efficiency of artificial spawning in fish. Quality of salmonid and sturgeon sperm was impaired after in vitro exposure to heavy metals. The degree of this toxic effect was species-specific. It was demonstrated that sperm motility parameters appeared to be good indicators of adverse effects of heavy metals fish sperm. The protection role of seminal plasma against toxic effects of heavy metals was suggested for salmonid fish. Oral application of 4-nonylphenol (NP) disrupted reproduction in pikeperch. In juvenile fish a decrease in the percentage of males and an increase of intersex fish was observed in relation to dose of NP and time of exposure to this alkylphenol. Exposure of adult males to the NP led to the reduction in fecundity, milt quality and fertility.
[Show abstract][Hide abstract] ABSTRACT: The objective of the studies was to analyse the process of oogenesis in vimba from a non-migratory population living in the waters of Drawieński National Park in north-west Poland. The character of spawning of this species is an obstacle in determining the right moment to catch spawners or developing artificial spawning biotechniques. Previtellogenesis of vimba begins about six months after hatching and lasts three years. The trophoplasmatic growth of oocytes (October-March/April) begins when carbohydrate vesicles appear near the nuclei oocytes of sexually mature females (aged 4+). Just before spawning, granulated, lipoprotein-like substances are cumulated. The resorption of pre-ovulation corpora lutea (non-ejected oocytes) and post-ovulation corpora lutea (ruptured theca folds and follicles) begins in the ovary of vimba in the middle of June. These were observed in histological cross sections for about two to three months. Describing the process of oogenesis can provide a foundation for developing practical applications in aquaculture aimed at preserving the biodiversity of the park's waters and this critically endangered species of the Polish ichthyofauna.