Erosion of the prismatic layer by the organic matrix during the formation of the nacre-prism transition layer in the shell of Pinctada fucata (Bivalvia, Mollusca)

Xiaojun Liu,Rongqing Zhang,Hongzhong Wang,Yujuan Zhou,Liping Xie,Juan Sun,Guilan Zheng,Guiyou Zhang,Chang Liu

doi:10.1007/s11434-011-4348-8

Abstract

Three variants of the sequence of formation of the nacre-prism transition layer were observed in Pinctada fucata (Bivalvia, Mollusca) shells. In each case, the layer was formed by the organic matrix secreted by the mantle, together with the interprismatic organic envelope. The continuity of the organic phase throughout the shell was maintained as the new nacreous layer was formed on the nacre-prism transition layer. Changes in the interprismatic organic envelopes on either side of the nacre-prism transition zone indicated that the organic matrix of the nacre-prism transition layer becomes embedded into the organic phase of the prismatic layer. It is concluded that penetration and erosion of the prisms by the organic matrix generates a strong bond between the prismatic and nacreous layers.

Highlights

Three variants of the sequence of formation of the nacre-prism transition layer were observed in Pinctada fucata (Bivalvia, Mollusca) shells
The prismatic layer is assembled on proteins produced by epithelial cells of the mantle margin, whereas the nacreous layer is laid down on proteins produced by the central mantle epithelium [8]
The nacre-prism transition layer is an organic layer that covers the internal surface of the prismatic layer (Figure 2(a))

Summary

Introduction

Three variants of the sequence of formation of the nacre-prism transition layer were observed in Pinctada fucata (Bivalvia, Mollusca) shells. The transition zone advances outward as the shell grows, in the course of which a sequential change occurs in the mantle epithelium, from laying down of the prismatic layer, to secretion of the transitional layer, to production of nacre. Little is known concerning these changes, and the mechanism by which these two different layers become closely joined remains uncharacterized We investigated this process by observing the changes that occur in the organic matrix during the formation of the nacre-prism transition layer in shells of P. fucata. Based on these observations, we propose an “embedment model” which explains the role of the organic matrix in the nacre-prism transition zone, and the strong adhesion between the prismatic and nacreous layers

Methods

Results

Discussion

Conclusion