This study examined the effect 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 Oil®; (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 significantly better than fish fed with commercial feed plus Dry Oil® (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.

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The susceptibility of 7 d old veliger larvae of the scallops Argopecten ventricosus and Nodipecten subnodosus, the penshell Atrina maura, and the Pacific oyster Crassostrea gigas to a pathogenic strain of Vibrio alginolyticus was investigated by challenging the larvae with different bacterial concentrations in a semi-static assay. The results indicate that the larvae of the 2 scallop species are more susceptible to the V. alginolyticus strain than those of the oyster and the penshell. Signs of the disease were similar to bacillary necrosis described in previous work. Interspecies differences in susceptibility to pathogens are discussed.KEY WORDS: Vibrio alginolyticus · Pathogenicity · Vibriosis · Mollusks · Scallops · Pacific oyster · Penshell Resale or republication not permitted without written consent of the publisherDis Aquat Org 49: [221][222][223][224][225][226] 2002 metabolites) of the immune system in adult Mytilus edulis are also present in the trochophore and veliger larvae of this species (see review of Dyrynda et al. 1995). Recently, Mitta et al. (2000) found that synthesis of the antimicrobial peptide mytilina occurs during metamorphosis of larvae of Mytilus galloprovincialis, and the antimicrobial peptide defensin is detected when metamorphosis is finished.In the present paper, veliger larvae of 4 bivalves, comprising 2 scallops (Argopecten ventricosus and Nodipecten subnodosus), a penshell (Atrina maura) and the Pacific oyster (Crassostrea gigas) were challenged with different concentrations of Vibrio alginolyticus selected from several strains of the same and other species (V. tubiashii, V. parahaemolyticus, V. vulnificus and V. campbelli) tested in 24 h bioassays on veliger larvae of A. ventricosus. V. alginolyticus was isolated during bacterial screening in a shrimp hatchery. MATERIALS AND METHODS Bacteriology.A Vibrio alginolyticus strain named APSA2 was isolated from a hatchery of white shrimp (Farfantepenaeus vannamei) postlarvae, in La Paz, Baja California Sur, Mexico, during bacterial screening. The isolate was identified as V. alginolyticus by Dr. John McInroy at Auburn University, Alabama, USA. The strain was kept in Luria-Bertani medium (LBM) containing 3% NaCl and stored at 4°C until needed. For the susceptibility assays, liquid bacterial cultures were prepared in trypticase soy broth (TSB) (Difco). To find the optimum salinity for bacterial growth, a preliminary assay was run by inoculating the strain into TSB media containing 0.5, 2.0, 5.0, and 10.0% NaCl. Cultures were incubated at 28°C, and growth was estimated by reading absorbance of the cultures in a Spectronic Genesys 2 spectrophotometer at 580 nm, and at 0, 2, 4, 8, 10, and 24 h from inoculation. With these results (Fig. 1), bacterial cultures were subsequently prepared in 2% NaCl TSB.Bivalve larvae. Adult Argopecten ventricosus, Nodipecten subnodosus, Atrina maura, and Crassostrea gigas, were brought to the hatchery at Centro de Investigaciones Biologicas del Noroeste, La Paz, and were conditioned for spawning...

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ABSTRACT. In aquaculture, probiotics have been tested for enhancing the immune system and promoting growth and survival rate of many marine species like shrimp and mollusks. In order to isolate bacteria with a high probiotic potential for marine shellfish aquaculture, homogenates of the gastrointestinal tract from adult mangrove cockle, Anadara tuberculosa, were obtained to perform in vitro and in vivo assays. Isolates were tested in vitro for hemolytic activity, hydrophobicity, tolerance to ammonia nitrogen, salinity and pH as well as for growth kinetics, extracellular enzymatic activity, autoaggregation, coaggregation and molecular identification. Three bacteria with high degree of hydrophobicity (>60% adherence to p-xylene) and four bacteria with medium hydrophobicity, which showed different patterns of attachment to monopolar solvents (chloroform and ethyl acetate) and a high tolerance to ammonia nitrogen (200 mg L -1 ), were selected. Six different treatments: T1 (without addition of cultured bacteria); T2 (MAt29, Enterococcus casseliflavus); T3 (MAt35, Citrobacter koseri); T4 (GAtB1, Bacillus subtilis subtilis); T5 (GAt7, Staphylococcus sp.); and T6 (1:1:1:1 mix of strains T2, T3, T4 and T5), were used to evaluate the specific growth rate, and cellular immune response of the shrimp Litopenaeus vannamei. The best specific growth rate was observed for T6 and T4 treatments related to Bacillus subtilis subtilis. A significant difference in total hemocytes count (P < 0.05) was found for T4 treatment with respect to control group. Strains isolated from A. tuberculosa had a beneficial effect on the growth and immune response of L. vannamei, so they have potential use as probiotics in aquaculture of marine shellfish. Keywords: Anadara tuberculosa, probiotics, bacilli, immune response, aquaculture.Aislamiento y caracterización de bacterias de la almeja "pata de mula" (Anadara tuberculosa) con potencial probiótico para el cultivo de camarón RESUMEN. En acuicultura, los probióticos han sido utilizados para incrementar respuesta inmune, crecimiento y supervivencia en especies marinas incluyendo camarones y moluscos. Con el propósito de aislar bacterias con un alto potencial probiótico para el cultivo de especies marinas, se obtuvieron homogeneizados del tracto gastrointestinal de adultos de "pata de mula" Anadara tuberculosa para realizar ensayos in vitro e in vivo. Las cepas se evaluaron in vitro para determinar actividad hemolítica, hidrofobicidad, tolerancia a nitrógeno amoniacal, salinidad y pH, cinética de crecimiento, actividad enzimática extracelular, autoagregación y coagregación, y finalmente se identificaron por métodos moleculares. Se seleccionaron siete bacterias; tres con alto grado de hidrofobicidad (>60% de adherencia a p-xileno) y cuatro con hidrofobicidad media, que mostraron diferentes patrones de adhesión a solventes monopolares (cloroformo y acetato de etilo) y alta tolerancia al nitrógeno amoniacal (200 mg L -1 ). Se realizó un ensayo in vivo para evaluar la tasa de crecimiento específico y la res...

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