Organic lining

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Fig. 1. The pore and its organic constituents; A: a pore in an inner chamber covered by an outer whorl, according to Leutenegger (1977), schematic, not to scale. B: Accumulation of mitochondria below a pore mouth in Bolivina sp., thus indicating the pores' main function: gas exchange. TEM micrograph of a section oblique to the surface ot the wall that exaggerates the thickness of the pore discs. The detachment of the outer lamella 2 (ouL 2) is an artifact of preparation. x 24,000. Courtesy S. Reber-Leutenegger. C: Resin cast of pores in the lateral chamber wall of Nummulites partschi De La Harpe with trabeculae. The carbonates of the shell are dissolved with HCl. SEM graph x 1,000. D: Outer pore mouths in the lateral suface of chamber wall of Assilina. Note the annular attachment of the interlamellar discs. SEM graph x 5,000. E: Inner pore mouths in the lateral chamber wall of Assilina shaped as eggholders (in order to keep the symbionts below their breathing chimneys). Note the annular suture of the pore plug. SEM graph x 5,000. C-E: from Hottinger, 1977. F: Perforation pattern on the dorsal surface of Challengerella persica (Recent, Persian Gulf): densely perforated porefields between imperforate ornamentation. SEM: oblique dorsal view of shell, x 30, and detail of porefield, x 500. G: Perforation pattern in Ammonia reyi Marie (Pliocene, Dar bel Hamri, Northern Morocco): densely perforated porefields between loosely perforated ornaments. SEM graphs of dorsal shell view (x 30) with detail (x 500). F-G: from Billman et alii, 1980; Abbreviations: bD: basal (pore) disc; Cy: cytoplasm; iL: inner lamella; ilD: interlamellar disc; iol: interlamellar organic lining; ls: lacunar system (in the cytoplasm); M: mitochondria; ML: median layer separating inner from outer lamellas; OL: Organic lining (here difficult to separate from plasmalemma of host); ouL 1: primary outer lamella; ouL 2, ouL3: subsequent outer lamellas; P: pore; Pc: organic pore coat; Pl: plasmalemma; ppl: pore plug (note its porosity); Spl: (biomineralized) sieveplate; V: vacuole; (Hottinger, 2006; fig. 75)[1] CC/BY-NC-SA)

Fig. 2. Organic lining; A: Lockhartia haimei (Davies), megalospheric specimen, axial section, transmitted light micrograph. From the Salt Range, Pakistan. Paleocene. Note the detachment of the organic lining from the inner surface of the biomineralized chamber wall by the first generation of cement deposited during early diagenesis. B-C: Planorbulinella larvata (Parker et Jones). Gulf of Aqaba, Red Sea; Recent; B: SEM graph of epoxy resin cast of a microspheric specimen. The subequatorial section of the shell reveals the detail of the early stages of growth, where the resin could not penetrate into the nepionic spiral chambers. After the dissolution of the mineralized shell, the organic lining alone documents the earliest chambers; C: megalospheric specimen, equatorial section, etched in order to reveal the organic lining and the lamellation of the chamber walls. The drying of the preparation before its coating for the SEM contracted the organic lining, detached it from the inner surface of the mineralized wall and broke the connection with the organic poreplugs at their weakest spot. This produced the circular holes in the organic lining of the preparation. Note the organic lining that coats the foramina connecting the first three chambers. ch: chamber; ch*: late spiral chamber filled with epoxy resin; f: foramen; ml: median layer of the primary chamber wall separating the inner from all outer lamellae; OL: organic lining; p: pore; (Hottinger, 2006; fig. 75)[2] CC/BY-NC-SA)


  • according to Hottinger (2006):

ORGANIC LINING - an organic cell envelope said to consist of mucopolysaccharides, located between the plasmalemma and the biomineralized cell envelope. It covers the protoplasmic cell body in the chamber lumina and the connecting cavities inbetween them (foramina, stolons), but never the interlocular spaces. Whether it occurs in chamberlet cavities of the supplemental skeleton is unknown at present. May be discontinuous or extremly thin over pore mouths and/or in the ultimate and penultimate chambers, and commonly thickens in the direction of earlier growth stages. May be involved in stolon plugging. May be resorbed together with the biomineralized wall when brood chambers are formed. The organic lining resists dissolution of the biomineralized shell by acidic attack, maintains the shape of the protoplasmic body and is capable of remineralizing its shell when the ambient environment returns to normal. However, the role of the organic lining in biomineralization has to be investigated further.

Remarks: There is no reason to abandon the traditional designation of organic lining (as used by Loeblich & Tappan, 1987) in favour of "inner organic lining" (IOL) as introduced by Anderson and Bé (1978). The eventual use of an "outer organic layer" called for by the IOL that might be applied either to the outer organic cover of the biomineralized shell or to the temporary organic envelope that in some species protects the process of chamber formation would add confusion in the description of the several layers of the cell envelope and their specific functions. Moreover, the term "inner organic lining" is easily confused with the term "inner lining" which is equivalent to "inner lamella", the inner calcified lamella of the primary wall in perforate foraminifera.

  • according to Schiebel and Hemleben (2017):

Inner Organic Lining (IOL) - Thick, dense layer between the inner test surface and the internal cytoplasm of planktic foraminifers.


Anderson & Bé (1978), Recent advances in foraminiferal fine structure research, In: Hedley R.H. & Adams C.G. (eds.), Foraminifera. Volume 3.- Academic Press, London, p. 121-202.

Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744.

Leutenegger S. (1977).- Ultrastructure de Foraminifères perforés et imperforés ainsi que de leur symbiotes.- Cahiers de Micropaléontologie, Paris, fasc. 3-1977, 52 p. + 54 pls.

Loeblich & Tappan (1987), Foraminiferal genera and their classification,Van Nostrand Reinhold, New York, vol. 1, 970 p.; vol. 2, 212 p. + 847 pls.

Schiebel & Hemleben (2017), Planktic Foraminifers in the Modern Ocean. Springer-Verlag GmbH Berlin Heidelberg, i-ivii + 358 pp. DOI: 10.1007/978-3-662-50297-6

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