The effect of a commercial probiotic (NanoCrusta, Altacrusta, Mexico City, Mexico) on the growth performance of Brachionus calyciflorus Pallas, 1766, was evaluated. In a first approach, probiotics were supplied in four densities (2.0 × 103, 1.1 × 105, 2.1 × 105 and 2.1 × 106 cells/ml), alone and in combination with Chlorella vulgaris (1 × 106 cells/ml). The test rotifer did not grow on the probiotic alone. However, when probiotics + C. vulgaris were added, the maximum densities (Dmax; ind/ml) and population growth rates (r) observed were higher. In the second experiment, probiotics were supplied at five higher densities (2.1 × 106, 4.2 × 106, 8.5 × 106, 1.7 × 107 and 3.4 × 107 cells/ml) with C. vulgaris and a control treatment with only C. vulgaris (probiotic‐free). Treatments supplied with probiotics between 2.1 × 106 and 1.7 × 107 cells/ml showed significantly higher Dmax and r than the control treatment. The results showed a positive effect of probiotic bacteria when supplied with C. vulgaris. The best outcome showed a Dmax 2.16 times and an r 1.63 times higher than the density of the control treatment. Growth rates were higher in the treatments with probiotics compared to the control. We conclude that application of NanoCrusta is feasible to improve B. calyciflorus production, but the effects need to be tested in larger scales.

We observed different morphotypes of some species in the family Brachionidae from the seasonal plankton samples of Lake Xochimilco collected during 2002-2003. We measured the body length, width, and spine lengths (posterior and anterior spines) of Brachionus havanaensis, Keratella americana, K. cochlearis and K. tropica during the periods when the predator Asplanchna brightwellii was present in great abundance but also when it was nearly absent. In general, spines of most of the selected rotifer species were longer if A. brightwellii was abundant. Relatively, small spines were observed if the predator was rare. The body lengths of brachionid rotifers widely varied in samples with more and less abundant A. brightwellii. Morphometric data are interpreted in terms of morphological adaptations of Brachionus and Keratella in response to Asplanchna predation.

Background: We studied the relationships between zooplankton distribution and environmental and trophic factors (abiotic variables, nutrients, bacterial biomass, and chlorophyll pigments) from three sampling surveys carried out during the three hydrological seasons (rainy, dry, and norte) in a tropical coastal lagoon connected to the sea. Results: Twenty eight (28) of the 54 taxa recorded were identified to species level, of which 3 genera of Cladocera were observed for the first time in the lagoon. Season-specific differences were highly significant. The overall zooplankton abundance was significantly higher during the dry season (157,000 ind.m −3 ) than those during the rainy and norte surveys (means of 11,600 and 16,700 ind.m −3 respectively). Copepoda (mostly nauplii) was the most abundant group (>83%) of total zooplankton abundance. Conclusions: Multivariate (coinertia) and multilinear regression analyses showed that transparency, salinity, temperature, pH, and food availability (Chl a, b, and c) were the main determinants of zooplankton abundance, composition, and diversity, explaining the seasonal differences. The relatively low zooplankton density in the lagoon compared to other eutrophic lagoons is attributed to the combined effects of high water exchanges, low depth, and high transparency, which favor instability and vulnerability to UV effects and/or to visual predation.

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In recent decades, an increasing interest in aquaculture for producing good quality and quantity of live food has led to the use of probiotics. Rotifers and cladocerans are important as live prey for fish and invertebrate larval rearing. We carried out an experimental study to evaluate the effect of a commercial probiotic (NanoCrusta®) on improving population growth of Brachionus angularis, Plationus patulus, Moina cf. macrocopa and Simocephalus mixtus. The probiotic was tested by direct supplementation (2.1 × 10 6 , 4.2 × 10 6 , 8.5 × 10 6 and 1.7 × 10 7 cells/ml) in addition to C. vulgaris as a source of food (1 × 10 6 cells/ml). The results indicated that probiotics enhanced maximum population density (D max) and the population growth rate (r) in both zooplankton groups. At 4.2 × 10 6 cells/ml, B. angularis improved their D max (62.74%) and r (28%) compared with probiotic-free control, while P. patulus enhanced their D max and r by 51.26% and 20.83% (probiotic at 8.5 × 10 6 cells/ml). The two lowest probiotic densities resulted in an improvement in the parameters compared with the probioticfree control treatments: M. cf. macrocopa enhanced D max by 14.82% and r by 18%, and S. mixtus incremented D max 10.92% and r by 10%. The addition of probiotic bacteria also resulted in an improvement in the rotifer egg ratio (ER). K E Y W O R D S aquaculture, live food, probiotic bacteria, zooplankton | 4483 CONTRERAS-TAPIA ET Al. essential zooplankton features that meet the requirements of the early stages of development (Snell, Johnston, & Matthews, 2019; Vadstein et al., 2018). Cultured zooplankton has benefits in contrast to naturally harvested zooplankton like more stable size, shape, availability, supply, nutritional quality and digestibility (Lubzens & Zmora, 2003). Microbial community management has a positive influence on developing better zooplankton culture conditions (Tang, Turk, &