POSSIBLE FUNCTIONS OF BIOMINERALIZATION OF SOME TEXTULARIID (FORAMINIFERA) SPECIES OF THE NW IBERIAN MARGIN

Abstract

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 analyses 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 elelemetal cocnentrations 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 are 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 refereed 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 contains high calcium content in their tests (such as T. deltoidea, T. agglutinans whereas some species much common in the deep sea includes high concentrations of lithogenic elements. Results of this work suggests 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 seems to be functions of biomineralization of the analyzed species and not only the intention of built a protective envelope.