Possible functions of biomineralization of some textulariid (foraminifera) species of the NW Iberian Margin
Résumé
The main goal of this work is to analyze the elemental composition of the test’s wall of some species/specimens of Textulariids (sub-class Subclass Textulariia), collected in surface sediments of the NW Iberian Margin. The elemental analysis was based on the Energy Dispersive Spectroscopy (EDS) on the Scanning Electron Microscope (SEM; Hitachi, S4100) of Textularia deltoidea, Textularia agglutinans, Sahulia conica, Karrerotextularia flintii, Siphotextularia heterostoma, Karreriella bradyi, Spiroplectammina sagittula and Arenoparrella mexicana. The elemental concentrations of the species wall were compared with the mineralogical composition (X-Ray diffraction) of the sediments of the stations where these specimens were collected. The results evidence that whereas the test’s wall of T. deltoidea, T. agglutinans, K. flintii and S. heterostoma is
characterized by the highest concentrations of Ca, Mg and Y and lowest Si and Al contents; S. conica, S. sagittula and K. bradyi present intermediate concentrations of the referred variables but display the highest K content; A. mexicana contains the highest Si and Al contents and lowest Ca, Mg
and Y concentrations. Some species that live in silisiclastic sediments contain high calcium content in their tests (such as T. deltoidea and T. agglutinans), whereas some species much common in the deep-sea display high concentrations of lithogenic elements. Results of this work suggest that some Textulariid species can use the test for “storage” and “excretion” of toxic or useless elements that can be used when necessary. These features seem to be functions of biomineralization of the analyzed species and not only the intention of building a protective envelope