Extracellular cracking and content removal of the benthic diatom Pleurosigma angulatum (Quekett) by the benthic foraminifera Haynesina germanica (Ehrenberg)

Field-collected living specimens of the benthic foraminifera Haynesina germanica were maintained in the laboratory and fed a naturally occurring motile benthic diatom assemblage dominated by Pleurosigma angulatum. The extracellular removal of diatom contents was inferred for P. angulatum in controlled experiments. A characteristic pattern of fracturing of the diatom frustule was observed that was directly attributed to foraminiferal feeding/sequestration mechanisms. These feeding/sequestration mechanisms have a potentially important bearing on our understanding of foraminiferal aperture morphology, foraminiferal evolution and the preservation of diatoms in marine sediments. Recognition of this characteristic breakage pattern of diatom frustules may provide insight into the natural importance of foraminifera in grazing diatom biofilms.