The aim of the study was to raise an issue concerning gonadal impairments in sturgeon reared in recirculating aquatic systems (RAS). In the present study, an in-depth histological evaluation in terms of gonadal pathologies was performed on over-4-year-old (1600 days post-hatching) Russian sturgeon (Acipenser gueldenstaedtii) reared under indoor RAS. A female-biased sex ratio, intersex occurrence, ovarian fat overgrowth, T-cell infiltration and follicle atresia were the most commonly observed disorders in the analyzed gonads. The combined processes of oocyte autophagy and follicular cell apoptosis were engaged in follicular atresia; however, atretic follicles showed a varied morphology, whereas oogonia and oocytes in the early stages of meiosis, as well as spermatogonia, underwent degeneration by apoptosis. The most severe pathology was observed in females with abundant intra-ovarian fat deposition. The extremely fatty ovaries were noted to lose the majority of ovarian follicles, which directly leads to fish sterility. The identified impairments might be related to estrogenic endocrine disruption, as feminization and unspecific vitellogenin synthesis were detected, although the sources of the observed pathologies can be diverse. Therefore, the presented research lays the groundwork for further studies on reproductive disorders in this prized and endangered fish species.

This study evaluates the effects of Advanced ActivePure technology, a photocatalytic air purification system, on the health status of mice housed in a controlled environment. This novel technology is promising due to its ability to eliminate the risk of ozone release into the environment, making it safer compared to other photocatalytic oxidation technologies. Utilizing 300 6‐month‐old mice over a period of 3 months, this research investigated various health parameters, including haematological, serum biochemical, redox, and inflammatory indicators. The experiment demonstrated no significant alteration in the majority of tested parameters between the control and Advanced ActivePure‐exposed groups. Until now, no study has analyzed the health safety of living organisms exposed to Advanced ActivePure in such a detailed manner. Histopathological analyses of nasal and eye tissues showed no adverse changes attributable to Advanced ActivePure exposure. These findings suggest that Advanced ActivePure technology does not negatively impact the overall health of mice, including biochemical markers and respiratory histopathology.