SREL Reprint #1987

Toxicity of the mixotrophic chrysophyte Poterioochromonas malhamensis to the cladoceran Daphnia ambigua

Douglas A. Leeperl and Karen G. Porter2

1Savannah River Ecology Laboratory, Drawer E, Aiken, SC, 29802, USA
2Institute of Ecology, The University of Georgia, Athens, GA 30602, USA

Abstract: The toxicity of the mixotrophic chrysophyte Poterioochromonas malhamensis to the common cladoceran Daphnia ambigua was investigated with laboratory survivorship experiments and observations of feeding behavior. When cultured autotrophically in an inorganic medium, P. malhamensis provided sufficient nutrition for survival and reproduction by D. ambigua. However, P. malhamensis grown heterotrophically on an organic medium (osmotrophically) in the dark or light was toxic to D. ambigua, killing all experimental animals within five days. Toxicity was not caused by the organic medium since daphnids fed the autotroph Chlamydomonas reinhardi that was grown in the organic medium had high survivorship. Changes in feeding behavior supported the results from the survival studies. Daphnids feeding in suspensions of heterotrophically cultured P. malhamensis exhibited significantly greater food rejection rates than animals fed autotrophically cultured P. malhamensis or C. reinhardi. Differences in the growth rate or biochemical pathways of heterotrophically versus autotrophically grown P. malhamensis likely influenced toxin production. Poterioochromonas may affect zooplankton feeding and behavior in nature if heterotrophic toxin production is comparable between phagotrophic and osmotrophic nutritional modes.

SREL Reprint #1987

Leeper, D.A. and K.G. Porter. 1995. Toxicity of the mixotrophic chrysophyte Poterioochromonas malhamensis to the Cladoceran Daphnia ambigua. Archiv fuer Hydrobiologie 134:207-222.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).