First data on secondary production of Philodina roseola (Rotifera, Bdelloidea) grown in laboratoryThe aim of this study was to quantify the secondary production of a benthic rotifer species, Philodina roseola grown in the laboratory. The variations in body size of this rotifer and its reproduction were individually determined for nine individual replicates. The measurements of linear dimensions (total length, width, and diameter) of the entire body or individual body parts were performed soon after birth and tracked throughout the individual life cycle. The biomass (µg DW/ind) was estimated by calculating body biovolume, which was determined by using the most suitable equations for the closest geometric shapes of different body parts. The individual production in body growth (Pg) and the reproductive production (Pr) were determined. The average length of the adult rotifer body (429.96 ± 28.12 µm) was about twice larger than the average size of neonates (198.77 ± 25.88 µm). The increase of biomass dry weight at different stages of development occurred at the same proportion; the biomass of an individual neonate (0.0104 ± 0.0014) was around half that of the juvenile (0.0254 ± 0.0029), and the biomass during adulthood (0.0508 ± 0.0071) was approximately twice that of the biomass juvenile. The results related to the body's production were obtained by computing the biomass value related to the mean body growth of the species (0.0425 ± 0.0172 µg DW/ind). The production regarding the increase in body mass between neonatals and juveniles was the highest, corresponding to 1.3 times the increase that occurred when the individual passed from juvenile to adult stages. The reproductive output was much higher (in average 5.8 times) than the body production, and that corresponded to 84.68 ± 3.65% of the total production value of Philodina roseola.