The digestive process of the dinoflagellate, <i>Oxyrrhis marina</i> Dujardin, feeding on the chlorophyte, <i>Dunaliella primolecta</i> Butcher: a combined study of ultrastructure and free amino acids

Abstract

SUMMARY The digestive process of Oxyrrhis marina Dujardin feeding on Dunaliella primolecta Butcher commences with the capture of the phototroph, perhaps involving trichocysts which restrain the prey, followed by engulfing by a membrane that appears to originate from near the fiagella pit of the O. marina. The prey, still within the capture membrane, enters the O. marina and is digested over a period estimated to be of the order of 12‐24h. During digestion the prey first becomes more electron dense and the contents coagulate. Later the prey becomes less distinct and disintegrates; by this stage remains from several prey may be enclosed within one vacuole. Small O. marina , captured by large prey‐depleted O. marina , suffer the same fate. Absence of any correlation between changes in intracellular amino acids and digestion of prey probably resulted from each O. marina containing several prey at various stages of digestion. However, the value of the glutamine/glutamate (Gln/Glu) ratio remained at around 0‐3, whilst the population changed from one dominated by N‐replete D. primolecta to one dominated by prey‐replete O. marina , N‐deplete D. primolecta and prey‐deplete O. marina both have Gln/Glu of &lt; 0.1. The Gln/Glu ratio may therefore be of use in assessing the nutrient status of heterotrophic microflagellates.