Effect of Fixative Solutions in Long-Term Bone Preservation.

Preservation of biological specimens over extended periods is essential for morphological research, especially in contexts where sample collection is limited or unrepeatable, such as spaceflight studies. However, the impact of long-term exposure to chemical fixatives remains underexplored. In this study, we used high-resolution X-ray microtomography and X-ray phase contrast tomography to investigate the stability of mineralized tissues subjected to prolonged chemical fixation. We examined the forelimb digits of geckos (Chondrodactylus turneri) preserved for over six years using a protocol involving formalin and ethanol, as well as the humeral bone of gerbils (Meriones unguiculatus) stored in fixative for more than four years. The gecko samples originated from the delayed vivarium control group of the Bion-M No. 1 space mission, offering a valuable chance to evaluate the preservation effects on specimens of significant scientific value. Comparative analysis revealed distinct changes in bone volume and linear attenuation coefficient of bone associated with formalin storage, highlighting the need for optimized storage strategies in long-term biorepositories. These findings offer valuable guidance for maintaining morphological fidelity in chemically preserved skeletal tissues.