Spectroscopic analysis of sequestered chloroplasts in Elphidium williamsoni (Foraminifera)

Foraminifera are unicellular, marine organisms that occur worldwide. A very common species in the German Wadden Sea is Elphidium williamsoni. Some foraminifera (such as elphidia) are able to use kleptoplastidy, which allows them to incorporate chloroplasts from their algal food source into their own cell body. The experiments reported here are based on the fact that chlorophyll (a and c) can be detected in the intact cells with spectroscopic methods in the visible spectral range, which allows an indirect investigation of the presence of sequestered chloroplasts. Starving experiments of E. williamsoni in the light (24 h continuous) showed that the greatest decrease in chlorophyll content was recorded within the first 20-30 days. From day 60 on, chlorophyll was hardly detectable. Through subsequent feeding on a renewed algal food source a significant increase in the chlorophyll content in foraminifera was noticed. The degradation of chlorophyll in the dark (24 h continuous darkness) during the starving period was much more complex. Chlorophyll was still detected in the cells after 113 days of starving time. Therefore, we hypotheses that the effect of photoinhibition applies to chloroplasts in foraminifera under continuous illumination.