Effect of potential probiotic bacteria on growth and survival of tilapia Oreochromis niloticus L., cultured in the laboratory under high density and suboptimum temperatura

This study examined the e¡ect of potential probiotic bacteria on growth and survival of the tilapia Oreochromis niloticus, under high density and suboptimum temperature. Presumptive Bacillus and lactic acid bacteria (LAB) were isolated from tilapia and from their culture system and were characterized for haemolytic and enzymatic activity, and antagonism against Vibrio. Selected strains were included in the diet of juvenile tilapia and evaluated during a 134- day assay. The experiment was conducted with four treatments: (1) fish fed with commercial feed plus Dry Oils; (2) fish fed with commercial feed plus LAB; (3) fish with bacilli in water; (4) fish with a mixture of treatments 2 and 3. Tilapias in all treatments, including bacteria, grew signiffcantly better than fish fed with commercial feed plus Dry Oils (control group). Survival was similar in all treatments. The physicochemical parameters of the culture system were maintained within the optimal ranges for the species, with the exception of temperature. Animals fed diet supplemented with bacilli and LAB had good survival and the best growth performance, suggesting that bacteria are appropriate growth-stimulating additives in tilapia cultivation

Effect of potential probiotic bacteria on growth and survival of tilapia Oreochromis niloticus L., cultured in the laboratory under high density and suboptimum temperature

This study examined the e¡ect of potential probiotic bacteria on growth and survival of the tilapia Oreochromis niloticus, under high density and suboptimum temperature. Presumptive Bacillus and lactic acid bacteria (LAB) were isolated from tilapia and from their culture system and were characterized for haemolytic and enzymatic activity, and antagonism against Vibrio. Selected strains were included in the diet of juvenile tilapia and evaluated during a 134- day assay. The experiment was conducted with four treatments: (1) fish fed with commercial feed plus Dry Oils; (2) fish fed with commercial feed plus LAB; (3) fish with bacilli inwater; (4) fish with a mixture of treatments 2 and 3. Tilapias in all treatments, including bacteria, grew signi¢cantly better than Fish fed with commercial feed plus Dry Oils (control group). Survival was similar in all treatments. The physicochemical parameters of the culture system were maintained within the optimal ranges for the species, with the exception of temperature (19.9-24.82 °C). Animals fed diet supplemented with bacilli and LAB had good survival and the best growth performance, suggesting that bacteria are appropriate growth-stimulating additives in tilapia cultivation

Assessment of endemic microalgae as potential food for Artemia franciscana culture

In this study, five microalgal strains were isolated from Bahía de La Paz, Baja California Sur, Mexico and identified as Grammatophora sp., Navícula sp., Rhabdonema sp., Schizochytrium sp., and Nitzschia sp., and their evaluation as potential food for Artemia franciscana. The isolated strains were cultured outdoors and harvested after four days. Chaetoceros muelleri was cultured under laboratory conditions and used as control. The protein, lipid, and carbohydrate composition and the fatty acid profiles of the strains were determined by gas chromatography. To assess the effect of microalgal strains on A. franciscana, decapsulated cysts were cultured at outdoor conditions in 15 L containers. The experiment was conducted for twelve days. Samples from the five different feeding treatments were taken at the beginning and end of the experiment to assess number, size, and weight of Artemia larvae. Treatment with Rhabdonema sp. showed larvae with a lower percentage of polyunsaturated fatty acids (PUFAs) while Grammatophora sp. showed those with the greatest PUFA proportion, even more than those fed Chaetoceros muelleri (control). Larvae consuming Schizochytrium sp. had no docosahexanoic (DHA) nor eicosapentaenoic (EPA) fatty acid content. Growth and survival of A. franciscana did not show significant differences among feed treatments, except when it was fed Nitzschia sp., showing lower survival and dry weight. Treatment based on Schizochytrium sp. and Rhabdonema sp. had a greater A. franciscana size but reduced dry weight; additional tests including two or more algal species for every treatment should be carried out to determine the best yield

Identificación y distribución de especies de "Meloidogyne" en Baja California Sur, México

Agriculture in Baja California Sur presents a serious problem due to the damage caused by the root-knot nematode Meloidogyne spp. The incidence of damage caused by this type of pathogen is high, however, its distribution and the species present in the entity are not currently known. Taking into account that this information is key in the strategies for the management of said phytonematode, the objective of the present study was to identify by morphological characters and molecular methods, the Meloidogyne species present in the sampled crops, as well as their distribution in the state. During the 2017-2018 agricultural cycle, soil and plant roots were sampled with wilt and yellowing symptoms in the different crops of four municipalities of the state. From 50 collected roots, 50 females of Meloidogyne spp. of the sampled crops, which were identified by morphological characterization of perineal patterns. Subsequently, genomic DNA was extracted from these females and specific genes reported in the literature for different species were amplified. The results obtained show that the identified species correspond to Meloidogyne incognita and Meloidogyne enterelobii, where the incidence of the populations was 30% and 70% respectively. Of the two-species identified, M. enterelobii was the one that predominated in the agricultural areas of Baja California Sur. While M. incognita was only found in two municipalities. This information will be useful in the effective implementation of control measures against the different Meloidogyne species in the State. Keywords: Meloidogyne spp., root knot nematode, vegetablesLa agricultura en Baja California Sur presenta un grave problema debido al daño provocado por el nematodo agallador Meloidogyne spp. La incidencia de daños provocados por este tipo de patógenos es alta, sin embargo, actualmente no se conoce su distribución ni las especies presentes en la entidad. Tomando en cuenta que esta información es clave en las estrategias para el manejo de dicho fitonemátodo, el objetivo del presente estudio fue identificar mediante caracteres morfológicos y métodos moleculares, las especies de Meloidogyne presentes en los cultivos muestreados, asi como su distribución en el estado. Durante el ciclo agrícola 2017-2018, se realizaron muestreos de suelo y raíces de plantas con síntoma de marchitez y amarillamiento en los diferentes cultivos de cuatro municipios de la entidad. A partir de raíces colectadas, se extrajeron 50 hembras de Meloidogyne spp. de los cultivos muestreados, las cuales, se identificaron mediante caracterización morfológica de patrones perineales. Posteriormente se extrajo ADN genómico de dichas hembras y se amplificaron genes específicos reportados en la bibliografía para diferentes especies. Los resultados obtenidos muestran que las especies identificadas corresponden a Meloidogyne incognita y Meloidogyne enterelobii, donde la incidencia de las poblaciones fue 30% y 70% respectivamente. De las dos especies identificadas M. enterelobii fue la que predominó en las áreas agrícolas de Baja California Sur. Mientras que M. incognita solo se encontró en dos municipios. Esta información será útil en la implementación eficaz de medidas de control contra las diferentes especies de Meloidogyne en el Estado. Palabras clave: Meloidogyne spp., hortalizas, nematodo agallad