Study of the effects of photoperiod and salinity in the Alvarado strain of the

The survivorship and distribution of planktonic rotifers are influenced by salinity and photoperiod. In this study we performed life table experiments with the estuarine rotifer Brachionus sp., “Alvarado” strain (collected in Veracruz, Mexico). Three salinities: 7.5, 15 and 30‰, and two photoperiods: constant light and 16:8 h (light:dark) photoperiod at one temperature (25±2°C) were assessed. The microalgae Nannochloropsis oculata (1×106 cells.mL−1) was supplied as food. We recorded the hatching percentages at different temperatures, and we included morphometric data of adult rotifers, neonates and parthenogenetic eggs. Results showed that the highest estimated values of net reproductive potential (Ro), intrinsic growth rate (r) and reproductive value (Vx) were obtained at 15‰ and 16:8 h (light:dark) photoperiod, followed by continuous light, respectively. The lowest reproductive rate was observed at 30‰ and 16:8 h (light:dark) photoperiod. Hatching reached 100% after 20 h at temperatures of 25 and 30°C. The morphometric analysis of the lorica suggests that this B. “Alvarado” strain belongs to the SM clade of the B. plicatilis species complex. This strain of Brachionus is: (a) euryhaline, (b) high growth rate, (c) small size. All these characteristics suggest that this strain can be potentially used as live food for larval fish and for the development of toxicity tests.We assessed the effects of photoperiod and salinity using life table bioassays with the rotifer Brachionus ‘Alvarado’. Adding, hatching percentages and morphometry of the lorica. The 15 ‰ and photoperiod (16: 8 h) are the best conditions to rotifer cultivation. The dimensions of B. ‘Alvarado’ including into the SM-clade. Perhaps, our strain coexists in sympatry with other lineages in the same aquatic system