Li, J.; Lu, J.; Wang, J.; Wang, Y.; Lai, J., and Yu, K., . Do diploid and haploid solitary cells of Phaeocystis globosa support the same copepod grazing, survival, egg production, and hatching success?

The food quality of phytoplankton affects the reproductive success of predators. Phaeocystis globosa blooms have negative effects on marine environments. However, the quality of P. globosa cells for predators is still under debate. The hypothesis that the nutritional value of diploid and haploid solitary cells would be different for the calanoid copepod predator Parvocalanus crassirostris was tested. The fatty acid compositions of diploid and haploid solitary cells and the effects of these cells on copepod grazing, survival, egg production, and hatching success were evaluated. In contrast to haploid solitary cells, diploid solitary cells did not contain C20:5ω3 (EPA) and C22:6ω3 (DHA) and were deficient in polyunsaturated fatty acids. Parvocalanus crassirostris individuals ingested more diploid than haploid cells. Egg hatching success was similar between the diets with diploid and haploid cells. Copepod survival and egg production were strongly inhibited by feeding on diploid cells. In contrast, they were high when copepods fed on haploid cells, reaching levels as high as those observed when the copepods fed on optimal diets of Isochrysis galbana and the diatom Thalassiosira weissflogii. The results suggest that diploid solitary cells of P. globosa are a poor food, whereas haploid solitary cells of this species are a nutrient-rich food for copepods.

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