Osseous Layer Research Articles

Fine structure of scale development in the teleost, Brachydanio rerio.

AbstractMature and embryonic scales of the zebrafish, Brachydanio rerio, were examined by light and electron microscopy. Each scale consists of a mineralized “osseous layer” superficially and a deeper, non‐mineralized, “fibrillary plate.” The mineralizing matrix contains randomly oriented filaments in decalcified sections, whereas the fibrillary plate is composed of orthogonally arranged lamellae of banded collagen fibrils embedded in electron dense material.Scale papillae and small scales first appear in the midbody region of fry between 0.95 and 1.14 cm long. The matrix of the osseous layer is produced prior to the fibrils of the fibrillary plate. Foci of mineral deposition appear in this matrix soon after its production, and increase gradually in number and extent. Cells surrounding the periphery of the scale are continuous with two layers of cells beneath the inner surface and with two layers extending a variable distance over the superficial surface. These “scale‐associated” cells are separated from the dermal collagen by other investing cell processes. The probable roles of these cells in scale formation are discussed and the need for further investigation of the fish scale as a mineralizing system is stressed.