Odd pairs

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Fig. 1. Odd association and polar structures in Praealveolina tenuis Reichel. From Alcantara, Lisbon; Cenomanian. Transmitted light micrographs. A: microspheric specimen, axial section; B: megalospheric specimen, axial section; C-E: odd partners: C: axial section of microspheric Simplalveolina sp.; D: axial sections of megalospheric Simplalveolina sp.; E: Ovalveolina sp, axial section. F: microspheric P. tenuis, axial section, detail showing polar structure with floors and shaftsin the basement. G: model of two subsequent chambers near their polar ends where the first floors in the basement appear. H: model of the protoplasmic body filling the cavities in G. Both models schematic, not to scale, after Reichel, 1933. a: aperture: af: apertural face; bchl: basement chamberlets; bl: basal layer; chl: (main) chamberlets; fl: floor; prp: preseptal passage; rp: (incipient) residual pillar; s: septum; sa: supplementary aperture; sh: shaft; sl: septulum; sut: cameral suture; (Hottinger, 2006; fig. 70 [1] CC/BY-NC-SA)


Definition

  • according to Hottinger (2006):

ODD PAIRS - (or associations); (Français: associations dépariées) common associations of two or more foraminiferal species that exhibit an identical or a closely related architecture in their adult form but differ markedly in their adult size. In most cases, the difference in the size of the adults is matched by a corresponding, size-dependant architecture in the megalospheric embryo, i.e. a large embryonal apparatus in the larger form, versus a simple, more or less undifferentiated megalosphere in the odd partner. These partnerships are usually restricted to one or two pairings of species. An example of a recent odd pair is the frequent association of Amphisorus hemprichii with the odd partner Sorites orbiculus. They have the same habitat on seagrass leaves but reproduce at different times in the seasonal cycle (Hottinger, 1999).



References

Hottinger (1999), "Odd partnership", a particular size relation between close species of larger foraminifera, with an emendation of an outstandingly odd partner, Glomalveolina delicatissima (Smout, 1954), Middle Eocene, Eclogae geologicae Helvetiae, Basel, vol. 92, N° 3, p. 385-393.

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