The osmotic fragility of erythrocytes serves as a crucial parameter indicating the cells' ability to endure variations in the osmotic environment. Disorders in this attribute are often correlated with a spectrum of pathologies, encompassing hemolytic anemias, malignant tumors, and cardiovascular dysfunctions. Notably, osmotic fragility exhibits variability across different animal species and closely intertwines with their respective ecosystems. A methodology for assessing osmotic fragility has been devised utilizing a laser particle analyzer, facilitating the real-time monitoring of cell concentration changes under controlled temperature conditions. The species examined include Homo sapiens, Rattus norvegicus domestica, Coturnix japonica domestica, Rana ridibunda, Carassius carassius, and Lampetra fluviatilis. The methodology is presented in two variants: (1) manual water additions and (2) automated medium dilution. Key parameters characterizing osmotic fragility include H50 (the osmolality causing lysis in half of the susceptible cells), H90 (lysis in 90% of the cells), and W (heterogeneity in lysis fragility within the cell population). The findings obtained through the developed method did not show statistically significant deviations from the results obtained using spectrophotometry and flow cytometry concerning parameters such as H50 and W. Moreover, no noteworthy disparities were observed between the outcomes of the automatic and manual methodologies. Erythrocytes of aquatic and semi-aquatic animals exhibit significantly higher resistance to hypotonic lysis. Among all species examined, amphibian (Rana ridibunda) and lamprey (Lampetra fluviatilis) erythrocytes demonstrated the lowest osmotic fragility. The most pronounced variability in resistance levels was detected among amphibians, with differences nearly doubling in comparison to other taxa examined. While mammalian erythrocytes (including those of humans and rats) exhibited similar fragility levels, they displayed less uniformity in their resistance profiles. Bird erythrocytes, on the other hand, demonstrated a half-lysis occurrence at higher osmolality levels compared to mammalian erythrocytes. Nonetheless, bird erythrocytes (Coturnix japonica domestica) lysed over a considerably wider osmotic range and contained a subset of cells resilient to hypotonic lysis. These findings indicate that erythrocytes of lower vertebrates possess lower osmotic fragility compared to those of higher vertebrates, a phenomenon likely attributable to embryonic characteristics, ecto-/endothermy, and habitat considerations.
