ABSTRACT. Tropical gar (Atractosteus tropicus) is currently exploited regionally as food and commercialized in the aquarium trade. Natural populations of A. tropicus may already be negatively affected by anthropogenic alteration of the areas in which it is distributed. However, it is necessary to deepen the knowledge for the optimization of its culture. A. tropicus cultured in three stocking densities: 100, 200, and 300 ind m-3 (D4, D8, and D12, respectively) were used in the present study to examine the effect on growth, survival, and condition factor. At the end of the eight-week trial, D4 was statistically superior in weight, length, and SGR compared to D12. While D8 was statistically similar to D4 and D12 in weight and length. There were no significant differences in the survival and condition of the fish. The optimum density in the production systems generates the optimal use of resources and the increase in the profitability of the system. Based on the results, it is recommendable a stocking density of 200 fish m-3 for an increase in the profitability of the culture infrastructure for its production as food or ornamental purposes.

ABSTRACT Short-tailed pipe fish (Microphis brachyurus) is a freshwater organism with high economic potential for the aquarium hobby, so it is necessary to implement methods to promote its culture through studies of digestive physiology. General activities of acid and alkaline proteases were evaluated, as well as the effect of pH, temperature and inhibitors. The optimal pH of stomach proteases was 2, while the optimal pH of intestinal proteases was 10. Optimal temperature for the acidic proteases was 35 ºC, while for alkaline proteases it was 45 ºC. Thermal stability showed high resistance at 35 ºC for both acid and alkaline proteases (above 100% residual activity). Acid proteases are resistant at pH 2 (50% of residual activity), meanwhile alkaline proteases were highly resistant at pH 10 (90% of residual activity). Acid proteases were inhibited by 80% with pepstatin A and alkaline proteases were inhibited with TLCK and TPCK for trypsin (75%) and chymotrypsin (80%), respectively. Finally, metallo-proteases were 75% partially inhibited some serine proteases by 75% with EDTA. In conclusion, M. brachyurus has a good digestive capacity, since they can degrade a wide variety of proteins due to their greater proteolytic activity.

RESUMEN El pez pipa (Microphis brachyurus) es un organismo dulceacuícola con alto potencial económico para la acuarofilia; sin embargo, es necesario implementar su cultivo a través de estudios de fisiología digestiva. Se evaluó el efecto del pH, temperatura e inhibidores sobre las actividades enzimáticas de proteasas ácidas y alcalinas. El pH óptimo de proteasas estomacales es de 2, mientras que el de proteases intestinales es de 10. La temperatura óptima de proteasas ácidas es de 35 ºC y las alcalinas de 45 ºC. La estabilidad térmica para proteasas ácidas y alcalinas es a los 35 ºC (más de 100% de actividad residual). La estabilidad a los diferentes pH de las proteasas ácidas es en 2 (50 % de la actividad residual), mientras que para las proteasas alcalinas es en 10 (90 % de la actividad residual). Las proteasas ácidas fueron inhibidas en 80% con pepstatina A y las proteasas alcalinas fueron altamente inhibidas con TLCK para tripsina (75%) y TPCK quimitripsina (80%). Finalmente, las metaloproteasas fueron inactivadas con EDTA en 70%. En conclusión, M. brachyurus tiene una buena capacidad digestiva al degradar una amplia variedad de proteinas debido a su alta actividad proteolítica.

ABSTRACT: The gar, Atractosteus tropicus is a native fish distributed in fluvial systems of the Mexican southeast, which presents aquaculture potential in the food industry and as ornamental species. However, it is necessary to deepen the knowledge for the optimization of its culture. The present study examined the effect of three feeding frequencies on the growth, survival, and condition of juveniles. The fish (90) were placed in nine 35 L tanks, (n = 10; three replicates per treatment). The feed (44% protein, 15% fat) was supplied to 2% of the biomass, divided into 2, 4 and 6 servings throughout 10 h for eight weeks. After eight weeks the standard length, wet weight, survival, Fulton K, specific growth rate, nitrogen carbon rate, the coefficient of variation and size heterogeneity were recorded, which were analyzed with a one-way ANOVA. There were no significant differences among treatments for any of the response variables. The overall results indicated that in general both the culture conditions and the three food frequencies tested were adequate for the species. The results indicate the high flexibility of the species to be cultured with minimum requirements of the food supply, which can translate into the optimization of production costs.

Wild populations of the green mojarra Cichlasoma beani, are being pressured by anthropogenic activities. It is possible to mitigate the deterioration of native species populations by developing culture techniques. Environmental factors such as light intensity and photoperiod may affect the development of fish under culture conditions. Therefore, the aim of the present study was to examine the effect of these factors on growth, survival, and condition of C. beani cultured in different light intensities and photoperiods. Light intensities of 1000, 1500 and 2000 lux and photoperiod 24:00, 16:08 and 08:16 Light:Dark (L:D) were tested in 40 L tanks (10 fish per tank, three replicates per treatment) during eight weeks. There were no significant differences in light intensity or photoperiod, which was associated with the natural adaptation of the species to these factors. The results also suggested the favorable overall growing conditions during the trial and he response of the life cycle stage of the specimens used in this study. The results of the present study indicate that the natural adaptations of C. beani, allow the favorable culture in various light conditions in juveniles, which can be advantageous for commercial culture as may imply low energy costs.

El sistema tradicional para producir botones florales de rosa de corte es ineficiente en las zonas productoras del estado de México, ya que muy pocos de ellos logran una alta calidad. El presente trabajo tuvo el objetivo de evaluar el uso de protectores florales solos o impregnados con fitohormonas (giberelinas o citocininas) para aumentar la calidad del botón floral. El protector floral impidió el ingreso de trips al botón floral e incrementó la calidad del botón floral tanto en la variedad Black Magic como en la Polo. El protector floral solo y con giberelinas contribuyó a aumentar la calidad del botón floral. Las citocininas utilizadas para impregnar tanto el botón floral como el protector floral aumentaron la calidad del botón en dosis óptima de 0,001 mg·L-1; sin embargo, dosis iguales o mayores a 100 mg·L-1 dañaron la estructura floral.

The present study was conducted to assess the use of floral protectors alone or impregnated with phytohormones (gibberellins or cytokinins) to increase bud quality. The floral protectors prevented the entry of thrips to the flower bud and increased the flower bud quality in the varieties Black Magic and Polo. The floral protector alone and gibberellin impregnated contributed to increase the quality of the floral buds. Cytokinins used to impregnate both the bud and the protector increased the quality of the floral buds at the optimal dosage of 0.001 mg·L-1; however, doses equal or above 100 mg·L-1 damaged the floral structure.