Abstract
Scale resorption was found to occur in the precocious male parr of the masu salmon (Oncorhynchus masou) during autumn and winter. A histological study was made on those resorbing scales and the associated cells.
Resorption commences at the posterior scale margin and advances gradually to the anterior. In a cross section, both the osseous layer and the fibrillary plate seem to be affected successively by the activity of cells attached around the resorbing margin. In the early phase of reorption, these cells show a morphological resemblance to those of the growing scale margin. After considerable destruction of the margin, however, there appear multinucleated giant cells which are similar to the osteoclasts of bone tissues.
It is presumed that the cells involved in the resorption of the scale may be derived from ancestor cells in the connective tissue of the scale pocket, or from a functional conversion of the scale forming cells.
