Paraffin Embedding of Gill Tissue

Fixed gill arches were trimmed to remove gill arch while the filaments were dehydrated in graded ethanol, cleared in xylene, and embedded in paraffin (Pathoprep 568, Fujifilm Wako Pure Chemicals, Osaka, Japan) (Wong et al. 2016 (link)). No decalcification was performed. Paraffin sections at 20 μm and 4 μm were prepared by a microtome (Leica RM2125 RTS, Leica Biosystems, Tokyo, Japan) for ISHCR and histology. The sections were mounted on MAS-coated slides (Matsunami, Osaka, Japan) and stored at 4°C until use. MAS-coated slides are glass slides coated with proprietary materials by Matsunami company, which allows the tissue to attach to the glass slide firmly under harsh washing conditions including high temperature and extreme pH.