WEKO3
アイテム
真珠層の成長機構
https://fra.repo.nii.ac.jp/records/2009050
https://fra.repo.nii.ac.jp/records/2009050be84ec21-9f4d-42f4-8f0b-b7c4d97733fc
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-06-27 | |||||
| タイトル | ||||||
| タイトル | 真珠層の成長機構 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Mechanism of growth of nacre in bivalvia | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
和田, 浩爾
× 和田, 浩爾 |
|||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 1) 真珠層の鉱物薄板の生成過程を電子顕微鏡によって観察し，真珠層の成長機構を生鉱物学的に考察した。 2) 鉱物薄板の成長前線は階段とテラスの部分とからなり，盛んに成長している真珠層表面に縞模様としてあらわれる。 3) 真珠層に階段ができる様式には次の三つがある。 1.ラセン転位の束を媒介とした成長によってできた単結晶の（001）面上の高さの大きい渦巻階段に由来する場合。 2.小傾角で接合した結晶群ないし結晶間の境界につくられる場合。 3.テラス面に生成した微結晶が接合して島状の鉱物薄板をつくる場合。 4) 二軸平均径が1000A以下の小さな結晶ｂは鉱物薄板の成長前線のあちこちに生成するが，アコヤガイの真珠層ではこのうちでも基板結晶の境界に生成した結晶が大きく成長する機会に特に恵まれている。 5) 結晶の厚化速度は二軸平均径が0.5～1.0μ に達する頃から急に遅くなり，そののち有機基質が結晶の（001）面の中央付近から附着しはじめ，厚さ方向の成長は殆ど完全に阻害され，横方向の成長がすすむにともない大きい平坦な（001）面の発達した板状結晶となる。 6) 散在して成長する結晶の形は生成条件に，その大きさは生成条件と生成後の経過時間に依存しており，鉱物薄板に包含された結晶の形と大きさは散在して成長した結晶が階段に接合する状態や時期によって変化する。 7) 真珠層の aragonite 結晶はそのｂ軸をinterlamellar matrix の昨日軸に平行に並べて成長し，ｂ軸に約±30度以内の乱れを含めると80～90%の結晶が繊維素に平行に成長している。 8) 真珠層の aragonite の（001）面にしばしば観察された渦巻および環状模様はこれの aragonite 単結晶がラセン転位を媒介として成長したことを想わせる。しかし単結晶は方位配列した沢山の crystallites が融合することによっても成長しており，真珠層の部分によって，また真珠層が成長する時の生成条件によっても著しく異なった成長をすると考えられる。 |
|||||
| 言語 | ja | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 1) Nacre shows laminar structure, consisting of alternate layers of interlamellar matrix and mineral lamella, in longitudinal and tangential sections of a shell. Individual aragonite crystals which consist of the mineral lamella show tabular form with well-developed (001) face, which is in parallel to the growing surface of the nacre, with the b axis in the horizontal growth direction of the layer. Intercrystalline matrix develops in between individual crystals (Grégoire, 1957; Wada, 1961). The mineral lamella has the height of 3000 Å,~6000 Å, whereas a reticulated membrane of interlamellar matrix is less than 200 Å, in thickness, in Pinctada fucata though both vary from species to species (Wada, 1961). 2) The growth fronts of mineral lamellae emerge on the growing surface of nacre to form a stepped surface (Fig. 1). The terrace of the mineral lamella is covered by thin membrane of interlamellar matrix (Figs. 3 and 4). The terrace, which is the (001) faces of aragonite crystals, exhibits narrow grooves at the boundaries between individual aragonite crystals (Figs. 3, 4 and 13). The layer patterns consisting of spirals or closed loops are seen commonly on the surface, which seems to suggest that individual aragonite crystals have grown immediately prior to the adsorption of the organic matrix (Figs. 3 and 5). 3) The following three are considered to be the process to create a new step on the surface of nacre. (a) The first type can be seen in Figs. 1 (shown by the arrow a) and 2, and illustrated schematically in Text-fig. 4A. The terrace originates from the step of the composite spiral having big step height on the (001) face of single crystal. As can be seen in Fig. 2, it is considered that the terrace T3 will be formed on the terrace T2, when the crystals a1, a2, .... join with the step S2 of the spiral. (b) The second type is the step resulting from the mismatch of the two slightly misoriented crystals or crystal groups, which can be seen in Fig. 3 and illustrated in Text-fig. 4B. (c) The third type is the step of small mineral lamella formed by the contact of small member of single crystals (Fig. 4 and Text-fig. 4C). From the steps of type (A) and (B), spiral hills will be formed, as pointed out by Wada (1961, 1966, 1968b.). The type (C) steps occur at the top of concentric hills (Wada, 1968b), or in the earliest stage of pearl formation and immediately after the hibernation of oysters (Wada, 1957 a, b). 4) Crystals which are responsible for the advance of the step grow on the terrace of the underlying mineral lamella. Large number of minute crystals occurs on all over the surface of the terrace (Figs. 13 and 14), but only a few crystals among them, especially those deposited near or at the boundaries between individual crystals in the underlying lamella, are allowed to grow larger than 0.5μ in diameter in Pinctada fucata (Figs. 3, 4 and 5). It is seen in Fig. 5 and Table 1 that the thickness of the crystals f14 ~f31 which are larger than 1.7μ in diameter is in the range of 0.32μ to 0.40μ, which agrees well with the thickness of the crystals f36 and f37 coalesced in the terrace. They have a large flat (001) face covered by reticulated organic matrix. The thickness of the crystal f10, about 0.5μ in diameter, is about 0.21μ, and is much smaller than that of the crystals f11~f13 (0.32μ~0.37μ in thickness and 1.4μ~1.6μ in diameter) which is similar to the step height of the mineral lamella. The (001) face of the crystals f10~f13 is convex and appears to grow rapidly in the vertical direction. It is evident that in the nacre of Pinctada fucata, interlamellar matrix is adsorbed on the (001) face of individual crystals about the time when the crystals reach to about 0.32μ ~0.43μ in thickness and 1.5μ~2.0μ in diameter. As a result, the growth normal to the basal plane is ceased, whereas the side faces can grow further, which results in tabular habit with larger flat (001) face. Then the individual crystals coalesce together to form a mineral lamellae. Probably just before the coalescence, inter-crystalline matrix is formed in between the crystals The above mentioned process is shown schematically in Text-fig. 7. 5) It is found that in the regions A, B and C crystals larger than 0.5μ in diameter occur in similar density at the growth fronts of mineral lamellae (Text-fig. 2), though their size becomes larger in general as we get nearer to the step and the basal face is flatter. In contrast to this, numerous minute crystals smaller than 1000 Å occur in the region D, as well as on the flat basal face of larger crystals and on the terraces of the underlying lamella exposed between larger crystals (Fig. 14). From these observations, the process of the formation of the lamella in the nacre of Pinctada fucata can be conjectured as follows. (a) Reticulate thin membrane of interlamellar matrix coveres completely the (001) face of closely packed crystals in the terrace, in the region A, resulting in the cessation of the growth of these crystals. (b) Since the growth normal to the basal face of the isolated crystals in the region B is ceased due to the adsorption of the matrix over the basal face, crystals have to extend latelally and join the step, sandwiching intercrystalline matrix in between the two. (c) The growth speed normal to the basal face of the isolated crystals in the region C is also slow down or ceased due to the adsorption of matrix, resulting in the lateral growth. (d) Nucleation takes place actively in the region D, and minute crystallites begine to appear at and near the boundaries of individual crystals in the underlying lamella. They grow rapidly in the direction both normal and lateral to the basal face. (e) When the crystals are formed more densely than a certain critical density on the underlying terrace emerged between larger crystals, it seems that they can hardly grow larger than 0.5μ, and that some are dissolved away into the mother fluid and others are coalesced into larger crystals. 6) In electron microscopic observations (Wada, unpublish), no evidence to be interpreted an alternate layer of mineral lamella and organic matrix can be found in the general profils of extrusion of secretory substances by the outer epithelial and mucous cells of a mantle. Nakahara (1961, 1962) described that mucous granules, which were secreted into the space surrounded by pearl-sac epithelium or between the mantle and shell, form fluidal substance, which shows a fine lamellar structure resembling nacreous layer prior to mineralization. If mineralization of nacre takes place in each lamellar capsule of organic matrix formed in the mucous layer, the conspicuous contradiction illustrated schematically in Text-fig. 5 is found in the crystal-interlamellar matrix relationship of nacre. It is probable that the amount of protein increases, acid mucopolysaccharides are reduced, and amino acid components are modified in the process of formation and mineralization of nacreous organic matrix (Wada, 1967, 1968b,). The present studies suggest that loose reticular or fine fibrous component with large amount of amorphous substance is polymerized and transformed into the closely reticulated membrane of interlamellar matrix of nacre (Figs. 11 and 12) and that the rate of polymerization and transformation of the organic component and/or of adsorption and incorporation of the component onto the basal face of isolatad and packed crystals are more or less different from part to part at the growth front of the terrace. In the above process, it is possible that the precursor of the matrix changes to have a stereochemical configuration with close affinity to the shell mineral, particularly on the active surface. Calcium for shell mineralization may be secreted through the mantle either in the form of complex with acid mucoprotein (Tanaka and Hatano, 1956) or inorganic ion (Horiguchi, 1959, 1968). Presumed that the inorganic calcium is supplied constantly and other factors influencing the concentration of [Ca++]x [CO3--] are negligible, crystallization of calcium carbonate may be interrupted at a certain interval due to the transformation and adsorption of the matrix, and will start again when calcium liberated in the course of transformation of the matrix reaches to a critical concentration. This is shown schematically in Text-fig. 6. The critical concentration of [Ca++]x [CO3--] to initiate nucleation is considered to be dependent upon the surface properties of the interlamellar matrix and seems to be not very high, as has already been discussed by Wada (1966a, 1968b). The ratio of the amount of inorganic calcium to calcium-mucoprotein complex secreted from the mantle is also considered to be one of the factors influencing the speed of thickening the crystal. 7) The morphology of isolated crystals seems to be dependent mainly on the concentration of [Ca++]x[CO3--] and the presence of organic substances, as well as the state of coalesence of the adjacent crystals. Closely packed crystals in a mineral lamella can not keep original form. 8) The size of crystals seems to have reverse relation to the density of occurrence of crystal, and is larger in the central region than in the marginal one of the Pinctada shell (Text-figs. 1 and 3). This means that the size of crystals is related to the concentration of [Ca++]x[CO3--]. 9) Oriented fibrils which appear to consist of rows of granules of diameter of 140 Å~200 Å are found in the replica of interlamellar matrix formed on the (001) face of aragonite crystals of nacre (Fig. 13), though the granular appearance of the fibrils is sometimes not very clean (Fig. 15). The b axis of aragonite is parallel to the fibrils, as seen in Fig. 15, and its (110) face is sometimes the fibrils. About 70~ 90% of crystals show this relation with fibrils of interlamellar matrix in Pinctada fucata. It is possible on the base of the above facts to conclude that oriented crystal- lization (epitaxial growth) of aragonite crystals takes place on the surface of interlamellar matrix which plays a role of a substratum, as pointed out by Wada (1961) and Grégoire (1962). 10) The typical brick-wall-like lamellar structure of nacre is considered to have been formed in the process of development of mineral lamellae, through the process shown in Text-fig. 7. However the such "brick-wall" appearance is not always revealed in the nacre of Pinna attenuata. 11) Spiral and closed loop patterns observed frequently on the (001) face of aragonite suggest that the single crystals have grown by the spiral mechanism around screw dislocations. But, in other instances, the single crystals look like to have grown by epitaxial settlement of many minute crystallites on the basal face of a larger crystal, or by coalescence in parallel orientation on interlamellar matrix (Wada, unpublish). These crystals exhibit complicated surface structures. It seems from these observations that the growth process of single crystals in nacre varies according to the difference of the growth conditions, about which will be discussed elsewhere in more detail in near future. | |||||
| 言語 | en | |||||
| 書誌情報 |
ja : 国立真珠研究所報告 en : Bulletin of the National Pearl Research Laboratory 巻 13, p. 1561-1596, ページ数 36, 発行日 1968-07-05 |
|||||
| 出版者 | ||||||
| 出版者 | 国立真珠研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | National Pearl Research Laboratory | |||||
| 言語 | en | |||||
| 書誌レコードID | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00091717 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | pearl_k_1561 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://jp-pearl.com/wp-content/uploads/2018/06/houkoku013.pdf#003 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本真珠振興会Archive | |||||
