Journal of Marine Biology

The fixation procedure for mammalian specimens is broadly similar to that used for fish; however, an important consideration is that fish tissues undergo autolysis and self-digestion much more rapidly. Moreover, it is necessary to replace conventional fixatives, particularly formalin, with plant-derived compounds, as formalin is associated with multiple adverse effects. In the present study, six fish brains were compared using two solutions: 10% formalin and a hydroalcoholic extract of rosemary (Rosmarinus officinalis). The findings indicated that rosemary extract can serve as a suitable fixative for fish specimens and organs, although its tissue penetration is lower than that of formalin. In addition, the extract induces a brownish discoloration of the specimens; this issue can be addressed by applying a chlorophyll decolorization technique. Based on the results of the current study and previous research, it can be concluded that plant extracts with antifungal and antimicrobial properties may be used as alternatives to formalin for tissue fixation.