Blue-green algae and selection in rotifer populations.

Observation in natural populations of the rotifer Asplanchna girodi suggested blue-green algae may have toxic effects on rotifers. The blue-greens Anabaena flos-aquae and Lyngbya sp. were isolated from a pond in Central Florida along with three electrophoretically identified genotypes of A. girodi. When tested Anabaena had marked effect on the reproductive rate of A. girodi and the effect was different among genotypes. Likewise, Lyngbya also depressed rotifer reproduction, but required an order of magnitude higher concentration to produce the same effects as Anabaena. The toxicity of these algae was corroborated by mouse bioassays. Results clearly show these blue-greens have the capacity to differentially reduce reproductive rates of rotifer genotypes. Because of this capability blue-greens could play an important role in the ecology of natural selection in rotifer populations.