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Predator–prey interactions are crucial components of populations and communities. Their dynamics depend on the covariation of traits of the interacting organisms, and there is increasing evidence that intraspecific trade‐off relationships between defense and competitive traits are important drivers of trophic interactions. However, quantifying the relevant traits forming defense–competitiveness trade‐offs and how these traits determine prey and predator fitness remains a major challenge. Here, we conducted feeding and growth experiments to assess multiple traits related to defense and competitiveness in six different strains of the green alga Chlamydomonas reinhardtii exposed to predation by the rotifer Brachionus calyciflorus. We found large differences in defense and competitive traits among prey strains and negative relationships between these traits for multiple trait combinations. Because we compared trait differences among strains whose ancestors evolved previously in controlled environments where selection favored either defense or competitiveness, these negative correlations suggest the presence of a trade‐off between defense and competitiveness. These differences in traits and trade‐offs translated into differences in prey and predator fitness, demonstrating the importance of intraspecific trade‐offs in predicting the outcome of predator–prey interactions. [ABSTRACT FROM AUTHOR]

We quantified the effect of two cyclopoids, an invasive (Mesocyclops pehpeiensis) and a native (Mesocyclops longisetus curvatus) species on the population growth of the rotifers Brachionus havanaensis and Brachionus calyciflorus. We hypothesized that the invasive copepod would have a greater adverse effect on the test rotifers. The population growth of B. havanaensis was tested in the indirect presence of B. calyciflorus (used as prey for the predatory copepods), and the predatory copepods, M. pehpeiensis and M. longisetus curvatus. For B. calyciflorus the experimental design was as above except that we used B. havanaensis as prey. The test rotifers were separated from the competitors and predators by mesh cages placed in the experimental jars. Rotifer density and the egg ratios were quantified, followed by a daily medium change, until the population density declined. The population growth rate of B. havanaensis ranged between 0.26 and 0.30 day−1, while that of B. calyciflorus between 0.19 and 0.21 day−1. The presence of the invasive copepod had an adverse effect on the smaller (< 110 µm) B. havanaensis, but not on the larger (> 180 µm) B. calyciflorus. The results are discussed with emphasis on the differences in the indirect impact invasive and native predatory copepods. [ABSTRACT FROM AUTHOR]

Maternal effect plays important role in adaptive evolution and population dynamics. Methylparaben (Mep) is a common organic pollutant exerting diverse impacts on aquatic organisms. However, the impact of maternal Mep exposure on offspring remains poorly understood. This study was designed to explore whether maternal Mep exposure can affect the offspring's population performance, either by amictic mothers in parthenogenesis phase, or by mictic mothers in sexual reproduction phase of the rotifer Brachionus calyciflorus. Here, we exposed either amictic or mictic mothers from one clonal laboratory population to 20 mg/L Mep (T environment) until the offspring or resting eggs were collected. A parallel control group without Mep (C environment) was also set. Thereafter, offspring from amictic mothers or stem female from resting eggs of mictic mothers were treated similarly in T or C environment. Population growth, life history traits and antioxidant indices of the offspring were examined. The results demonstrated that maternal Mep exposure inhibited population performance of offspring in both life history phases, while the negative effects were markedly buffered in sexual reproduction phase. This study clarifies toxicity of Mep on rotifers and highlights the different response patterns of maternal Mep exposure in different life history phase. [ABSTRACT FROM AUTHOR]

Climbing perch, A. testudineus (Bloch, 1792), is a widely consumed fish in Asian nations due to its high nutritional value and delicate meat. The main obstacles to the spread of its cultural practises are a scarcity of high-quality seed and larval rearing due to the low survival rates in the initial stages of larval development. The key to improving the seed production of this species may lie in strategies to improve larval survival in the early stages. As a result, the goal of current study was to evaluate the impact of vitamin C, selenium, and highly unsaturated fatty acid (HUFA) enriched Brachionus calyciflorus on the development, nutrient availability, and fatty acid profile of climbing perch larvae. A total of 180 numbers of 3 days post-hatch (dph) larvae (0.021 ± 0.001 mg) were uniformly distributed among five treatments in triplicates. The larvae were fed thrice a day for 15 days with selenium (D 1), vitamin-C (D 2), HUFA (D 3) and combination of selenium-vitamin C- HUFA enriched (D 4) and non-enriched rotifer (C). The proximate analysis of various enriched and unenriched B. calyciflorus groups revealed that the vitamin C and HUFA-enriched treatment groups, respectively, had the highest percentages of crude protein (7.50%) and crude lipid (2.51%). Whereas, larvae fed a combination of selenium-vitamin C- HUFA enriched (D 4) rotifer showed the highest percentages of crude protein (12.40%) and crude lipid (1.81%). The findings of the fatty acid analysis demonstrate that feeding Se-VC-HUFA enriched B. calyciflorus to larvae resulted in significantly greater concentrations of Eicosapentaenoic acid (9.38%) and Docosahexaenoic acid (11.05%) that are 3.07 and 7.67 times higher, respectively, than feeding unenriched B. calyciflorus to larvae. The highest DHA/EPA ratio (1.18) was also observed with larvae fed Se-VC-HUFA enriched B. calyciflorus. The survivorship analysis revealed that the D 4 treatment group fed a combination of Se-VC-HUFA-enriched B. calyciflorus had the highest survival (37.41%) and the lowest (18.70%) observed in the control group. The highest average body weight gain and increased growth (30.79 ± 1.11 mg) were seen in the fishes given the rotifer supplemented with D 4 group, which performed substantially better than the other treatment groups (P < 0.05). Weight-specific growth rate (W-SGR) and Length-specific growth rate (L-SGR) of the fish exhibited similar trends across all treatment groups, whereas significantly (P < 0.05) lowest condition factor was observed in D 4 (2.63 ± 0.01) and highest in control group (3.21 ± 0.01). The results showed that larvae fed with enriched rotifer had significantly higher (P < 0.05) growth, nutrient availability, and fatty acid profile compared to un-enriched rotifer. The ideal first food for A. testudineus larval growth and survival must be a combination of Se-VC-HUFA enriched B. calyciflorus. • Enrichment of rotifer with nutraceuticals such as selenium, HUFA and vitamin C will improve the nutritional profile of rotifer as well as improves the larvae performance. • Better larval growth and survival could be achieved by feeding with enriched B. calyciflorus. • Feeding B. calyciflorus enriched with Selenium-Vitamin C-HUFA leads to increased body weight gain and specific growth rate in climbing perch larvae. • Higher larval growth and survival rates are positively correlated, suggesting that dietary DHA and EPA levels are essential for the proper development of climbing perch larvae. [ABSTRACT FROM AUTHOR]