On the predatory behavior of Oxyrrhis marina (Dinophyceae) feeding on Pyramimonas grossii (Prasinophyceae)

Abstract: 
The feeding behavior of the dinoflagellate Oxyrrhis marina with the prasinophyte Pyramimonas grossii as prey was studied in order i) to determine the ingestion rate for this armed microalga, ii) to survey the impact and fate of ejectisomes discharged within predatory cells, and iii) to check if birefringent bodies occur in both, starved and fed Oxyrrhis cells. Oxyr-rhis which was grown to stationary phase and then added to cultures of Pyramimonas captured and digested more than 95% of the prasinophyte within ten days. The decline of non-digested Pyramimonas cells monitored by regular cell counting using light microscopy, was also measured by fluorescence emission spectroscopy and registered by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Transmission electron microscopy revealed that the ejectisomes of Pyramimonas which were discharged within the food vacuole did not harm Oxyrrhis. Mainly the body scales and the ejectisomes were not digested but excreted. Both, starved and fed Oxyrrhis cells contained birefringent bodies. Besides the longitudinal banding, a faint and rather oblique running striation was registered for them.