High resolution electron microscopy studies of the silica lorica in the choanoflagellate Stephanoeca diplocostata Ellis

Abstract

The silica lorica of Stephanoeca diplocostata Ellis has been studied by ultra-high and high resolution electron microscopy. Ultra-high resolution electron microscopy reveals an extremely amorphous silica structure within costal strips. T-junctions between strips in intact loricae have been examined and in several cases strips of viscid connective material containing in part amorphous silica have been observed running between the two strips. Silica demineralization initiates from the central axis of the costal strips leaving tubular brittle rods. The surface of costal strips is shown to be active in binding low concentrations of cations (Co$^{2+}$, Fe$^{3+}$) from external solutions.