(2003) isolated a protein complex composed of pearlin and pearl keratin from the nacreous layer
of pearl beads and oyster shells, which could induce aragonite crystallization.
This suggested that BMP-2 has a key role in the nacreous layer
The elements in prismatic layer and nacreous layer
of Haliotis discus hannai Ino shells were analysed using Energy dispersive spectrometer.
"If we rear the oyster for a longer period, the lustre of the nacreous layer
might be decreased, because the surface of the nacreous layer
becomes more irregular," said Dr Hiromichi Nagasawa, a scientist at the University of Tokyo.
Internal growth annuli were defined as areas of discontinuity of the prismatic layer that extended from the nacreous layer
to the periostracum (Fig.
But it is the aragonite form found in the inner, nacreous layer
that makes the shell remarkably resistant to breakage.
Whole shell destruction does not allow for discrimination between shells that have a thicker proportion of a layer such as the prismatic layer to the periostracum or nacreous layer
Once the outer prismatic layer has reached full thickness (80-90 [micro]m in Laternula rostrata), a nacreous layer
is secreted below (Aller, 1974).
Thickness of the nacreous layer
of all pearls was measured using a coherence tomographic scanner (OSLF-1500; Shenzhen Certainn Technology Co., Ltd.).
Transition to the nacreous layer
. The transition between the prisms and the underlying nacre of pteriids and pinnids starts with the production of an organic pellicle, which first appears over the interprismatic walls and then extends toward the prism center, until it covers the entire surface (Fig.
The prisms of the prismatic shell layer are composed of single-crystal fibers radiating from spheruliths, whereas in the nacreous layer
the structure is similar to that of a brick wall, with tablets in each layer offset with respect to those in the layers above and below them.
At the beginning of the nacreous layer
, experimental animals showed several (5-7) superimposed lamellae consisting of unconnected round tablets.