ABSTRACT Pacific red snapper (Lutjanus peru) is an important commercial species in Mexico with great aquaculture potential; however, digestive physiology is still unknown. Therefore, the objective of the present work was to characterize the digestive proteases of L. peru juvenile using biochemical and electrophoretic techniques. Results showed a higher acid protease activity than the alkaline proteases, trypsin, chymotrypsin, and leucine aminopeptidase (LAP). The optimum temperature for acid proteases was between 30 to 40°C. Trypsin activity showed two maximum peaks of temperature (30 and 50°C), while alkaline proteases, chymotrypsin, and LAP had optimum temperatures of 50, 50 to 60, and 40°C, respectively. Moreover, the optimum pH of acid proteases was between 2 and 3. Also, alkaline proteases, trypsin, chymotrypsin showed pH optimums at pH 6, 9, and 5, respectively, although LAP showed two optimum pH values at 6 and 9. Acid protease zymogram showed three isoforms, totally inhibited by pepstatin A. Alkaline protease zymogram revealed six bands (125.4, 67.2, 57.9, 48.6, 29.8, and 26.9 kDa), which were inhibited by specific serine-proteases and metalloproteases inhibitors. In conclusion, the main digestion in L. peru depends on stomach proteases, which are characteristic of carnivorous fish, followed by intestinal digestion supported mainly by chymotrypsin.

ABSTRACT In the Southeast of Mexico, there are many native cichlids with commercial interest such as redhead cichlid (Vieja melanurus) and twoband cichlid (V. bifasciata), which have a great local demand and excellent meat quality. However, it is necessary to implement their culture based on nutrition studies and digestive biochemistry. This study’s objective was to characterize these two cichlids’ digestive proteases (pH, temperature, and inhibitors) through biochemistry techniques. Results showed that V. melanurus and V. bifasciata have a digestive capacity analogous to other omnivore fishes, where the optimal pH values of stomach proteases (4 and 2, respectively) and intestinal proteases (6 and 12, respectively), the optimal temperature of acid (35°C and 55°C, respectively) and alkaline proteases (45°C and 55°C, respectively) are quite similar. Both species presented high thermal and pH stabilities. Inhibition showed that V. melanurus is more sensitive to specific inhibitors for alkaline proteases than V. bifasciata. In conclusion, V. bisfasciata and V. melanurus have different digestive protease patterns. Both species can hydrolyze different protein ingredients to formulate a specific diet. Nevertheless, V. bifasciata is more resistant to the presence of inhibitors, which allow it to include vegetable proteins in its diet.

RESUMEN En el sureste de México, existen muchas especies de cíclidos nativos de interés comercial como el cíclido rojo (Vieja melanurus) y el cíclido de dos bandas (V. bifasciata), los cuales tienen una gran demanda local y tienen una excelente calidad de carne; sin embargo, es necesario implementar su cultivo con base en estudios de nutrición y bioquímica digestiva. El objetivo de este estudio fue caracterizar las proteasas digestivas (pH, temperatura e inhibidores) de estos dos cíclidos nativos mediante técnicas bioquímicas. Los resultados mostraron que V. melanurus y V. bifasciata tienen una capacidad digestiva similar a otros peces omnívoros, donde los valores óptimos de pH de proteasas estomacales (4 y 2, respectivamente) e intestinales (6 y 12, respectivamente), la temperatura óptima de proteasas ácidas (35°C y 55°C, respectivamente) y alcalinas (45°C y 55°C, respectivamente) son muy parecidas. Ambas especies presentaron alta estabilidad térmica y de pH. La inhibición mostró que V. melanurus es más sensible a inhibidores específicos de proteasas alcalinas que V. bifasciata. En conclusión, V. bisfasciata y V. melanurus tienen diferentes patrones de proteasas digestivas, pero ambas especies pueden hidrolizar diversos ingredientes proteicos para formular dietas específicas; sin embargo, V. bifasciata es más resistente a la presencia de inhibidores, lo que permitiría incluir proteínas vegetales en su dieta.

Abstract: The design of specific feed based on digestive physiology, and an adequate feeding schedule, are important to reduce cannibalism and increase survival rate in larvae fish. The first objective of this study was evaluating growth, survival and cannibalism during tropical gar (Atractosteus tropicus Gill) larviculture, using four feeding schedules: CT (10 day co-feeding of Artemia nauplii and commercial trout feed), T1 (commercial trout feed), T2 (10 day co-feeding of Artemia nauplii and A. tropicus larvae designed feed) and T3 (A. tropicus larvae designed feed). The second objective was to determinate correlation between survival and cannibalism, using a linear regression model. We observed better growth and survival in the co-feeding treatments CT and T2. Cannibalism was observed in all treatments, with higher presence in T1 and T3 (treatments without Artemia nauplii co-feeding). It was observed a strong correlation between survival and cannibalism (r = -0.88, p < 0.05), demonstrating that cannibalism has a considerable effect on survival rate. We concluded that T2 represent the best alternative for A. tropicus feeding during larviculture, since they present better growth and less cannibalism.

Resumen: El diseño de dietas con base en la fisiología digestiva, así como un adecuado esquema de alimentación, permiten la disminución del canibalismo y el incremento de la supervivencia en la etapa larvaria de peces. Por lo anterior, el objetivo fue evaluar el crecimiento, supervivencia y canibalismo en la larvicultura del pejelagarto (Atractosteus tropicus Gill) bajo cuatro esquemas de alimentación: CT (co-alimentación con nauplio de Artemia por 10 días y dieta comercial de trucha), T1 (alimentación con la dieta comercial de trucha desde la apertura de la boca), T2 (co-alimentación con nauplio de Artemia y dieta diseñada para larvas de A. tropicus por 10 días) y T3 (alimentación con la dieta diseñada para A. tropicus desde la apertura de la boca), así como determinar la correlación entre el canibalismo y la supervivencia mediante un modelo de regresión lineal. Los mejores crecimientos y supervivencias se obtuvieron en los tratamientos T2 y CT. En todos los tratamientos se presentó canibalismo, siendo más alto cuando no se co-alimentó con nauplio de Artemia (T1 y T3). Se encontró una fuerte correlación (r = -0.88, p < 0.05) entre la supervivencia y el canibalismo, lo que demuestra que el canibalismo tiene efecto sobre la supervivencia. El tratamiento T2 representa la mejor alternativa para la larvicultura de A. tropicus, con mayor crecimiento y menor canibalismo.

ABSTRACT Tropical gar (Atractosteus tropicus) aquaculture is a potential economic activity in southeast Mexico. This study analyzed the economic profitability of tropical gar grow-out using two commercial feeds (Silver Cup® and Super®). The last one was designed based on the digestive physiology of the species. The experiment was conducted in six concrete ponds of 4 m3 (two treatments with three replicates) for 210 days; in each experimental unit 40 juveniles were stocked with an initial average weight and a total length of 104 ± 10 g and 27.7 ± 0.88 cm, respectively. At the end of the grow-out, there were statistics differences (P < 0.05) among treatments, where fish fed with Silver Cup® obtained the highest final average weight and total length (450.29 ± 5.36 g and 41.7 ± 1.81 cm, respectively), compared with fish fed Super®, which obtained a final average weight and total length of 415.05 ± 5.38 g and 41.4 ± 1.57 cm. Proximal analysis indicated a better protein content and fewer lipids in fish fed with Super®. The profitability analysis showed that fish fed with Silver Cup® diet had the highest values, with a Net Present Value (NPV) = US$55,332.63, Cost/Benefit (C/B) = US$1.5 and Internal Return Rate (IRR) = 48.38%, while for fish fed with Super® diet was NPV = US$50,852.28, C/B = US$1.49 and IRR = 47.03%. In conclusion, it is considered that both grow-out foods are profitable, although better nutritional value and less production cost are using Super® diet.

ABSTRACT The effect of different lipid levels (10, 15, 20 and 25%) and oil sources (fish oil: FO and soybean lecithin oil: LO) on growth, survival, digestive enzymatic activity, gene expression acetyl CoA carboxylase (ACC1) and fatty acid synthase (FAS) of Mayan cichlid larvae Cichlasoma urophthalmus were evaluated by a bi-factorial design. The larvae were fed from hatching with eight different experimental isoproteic diets (45% protein) and a commercial diet for tilapia as a control diet. The results showed that larvae fed the LO15 diet had the highest growth in weight and total length and higher trypsin activity. The lowest values in FAS and ACC1 expression were obtained exclusively with the lipid type (soybean lecithin). It is concluded that the inclusion of soybean lecithin at a concentration of 15% allows the 100% replacement of fish oil in balanced feed for the culture of Mayan cichlid larvae.

Abstract Background: Prebiotics are polysaccharides that cannot be digested by the host; however, they generate benefits by stimulating the activity of beneficial microorganisms in the digestive system, which can maximize weight gain, feed conversion, and stimulate the immune response. Mannan oligosaccharides (MOS) have been evaluated in several fish species of commercial importance. Goals: Determine inclusion effects of different MOS levels in balanced diets for juveniles of Atractosteus tropicus on the growth, productive parameters, survival, somatic indexes, and activity of digestive enzymes. Methods: Six experimental diets including MOS (0.0, 0.2, 0.4, 0.6, and 0.8%) and a trout control diet (DC) were designed, manufactured, and evaluated in triplicate during 62 days. A hundred and eighty juveniles (5.11 ± 0.08 g) were distributed in a recirculation system with 18 tanks of 70 L with a flow of 10 L min-1. Results: The 0.2% MOS diet produced the highest values in weight gained (WG), specific growth rate (SGR), and protein efficiency rate (PER) and the lowest value in feed conversion rate (FCR). Survival in all treatments was greater than 96%. The hepatosomatic index was higher for the 0.4% treatment, while the viscerosomatic index was higher for the 0.4% and 0.6% treatments. All the enzymatic activities (acid protease, alkaline protease, trypsin, chymotrypsin, leucine aminopeptidase, carboxypeptidases, lipases, α-amylase, acid phosphatases, and alkaline phosphatases) showed significant differences by the inclusion of MOS in the diet. Conclusions: Supplementation of 0.2% MOS in diets for juveniles of A. tropicus, generates benefits in growth and productive performance. The inclusion of MOS in diets for juveniles of A. tropicus modifies somatic indices and the activity of digestive enzymes of juveniles.

Resumen Antecedentes: Los prebióticos son polisacáridos no digestibles por el huésped, pero, por otro lado, son los encargados de estimular la actividad de microorganismos benéficos en el sistema digestivo, lo que puede maximizar la ganancia en peso, la conversión alimenticia y la activación de la respuesta inmune. Los oligosacáridos de manano (MOS) han sido evaluados en varias especies de peces de importancia comercial. Objetivos: Determinar el efecto de diferentes niveles de MOS integrados en dietas balanceadas para juveniles de Atractosteus tropicus sobre el crecimiento, parámetros productivos, supervivencia, índices somáticos y actividad de enzimas digestivas. Métodos: Se evaluaron por triplicado seis dietas experimentales con inclusión de MOS (0.0, 0.2, 0.4, 0.6 y 0.8%) y una dieta control de trucha (DC) durante 62 días. Se distribuyeron 180 juveniles (5.11 ± 0.08 g) en un sistema de recirculación con 18 tanques de 70 L con flujo de 10 L min-1. Resultados: La supervivencia en todos los tratamientos fue superior al 96%. La dieta 0.2% de MOS presentó los valores más altos en peso ganado (WG), tasa específica de crecimiento (SGR) y tasa de eficiencia proteínica (PER), y el menor valor en tasa de conversión alimenticia (FCR). El índice hepatosomático (HSI) fue mayor para el tratamiento 0.4%, mientras que el índice viscerosomático fue mayor para los tratamientos 0.4% y 0.6%. Todas las actividades enzimáticas determinadas mostraron diferencias entre tratamientos (proteasa ácida, proteasa alcalina, tripsina, quimotripsina, leucina aminopeptidasa, carboxipeptidasas, lipasas, α-amilasa, fosfatasas ácidas y fosfatasas alcalinas). Conclusiones: La suplementación de 0.2% de MOS en dietas para juveniles de A. tropicus genera beneficios en el crecimiento y el rendimiento productivo. La inclusión de MOS en dietas para juveniles de A. tropicus modifica los índices somáticos y la actividad de enzimas digestivas en juveniles.

ABSTRACT: Lipids requirement of tropical gar Atractosteus tropicus prejuveniles and juveniles was evaluated on growth, survival, chemical composition and apparent digestibility coefficient (ADC). Four semi-purified experimental diets (5, 10, 15 and 20% of lipids) were obtained with a mix of menhaden oil and soybean lecithin (2:1 ratio). Two trials were carried out, first with 600 prejuveniles of 0.5 g (35 days post-hatching, dph) for 56 days, and the second with 160 juveniles of 15 g (two-months-old) for 42 days. In the first trial, 15 (40.8 g) and 20% (40.2 g) lipid diets showed the best weight. Significant differences were obtained in condition factor (CF), daily lipid intake (DLI), hepatosomatic index (HSI), crude protein, ashes, nitrogen-free extract, moisture and ether extract between treatments. In the second trial, fish fed with the 10% lipid diet obtained the highest weight (89.1 g) compared with the other treatments. Significant differences were recorded for weight gain (WG), feed conversion ratio (FCR), specific growth rate (SGR), condition factor (CF), and lipid efficiency rate (LER). Also, significant differences were obtained in crude protein, ether extract, NFE, gross energy, apparent lipid ADC, protein ADC and dry matter ADC. The polynomial models applied to both trials indicated an optimum lipid requirement of 17% for 0.5 g juveniles and of 9% for 15.2 g juveniles.

ABSTRACT The present research was focused to characterize the digestive proteases in Macrobrachium carcinus adults using biochemical and electrophoretic techniques. Our results showed that the alkaline proteolytic activity from males and females did not show significant differences (P > 0.05) between them, the optimum pH for digestive proteases is 8, and is very stable to changes in alkaline pH (8 and 10). The optimum temperature for alkaline proteases is 45°C and is stable from 25 to 45°C. The activity was totally inhibited with phenylmethylsulfonyl fluoride (PMSF), additionally the inhibition with trypsin soybean inhibitor 1 (SBT1) and tosyl-lysine-methyl ketone (TLCK) indicate high effect over serine proteases. Eight active bands were found using sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE) zymogram (range 17.8-94.0 kDa), which were partially inhibited with ovalbumin (Ovo), SBT1, phenanthroline (Phen), tosyl-phenylalanine-methyl ketone (TPCK), TLCK and ethylenediaminetetraacetic acid (EDTA), indicating an omnivorous digestive capacity, which remarks that the mainly alkaline protease in M. carcinus hepatopancreas are trypsin like enzymes.

ABSTRACT. A total of 300 Centropomus undecimalis juveniles, with an average initial weight of 3.16 ± 0.28 g and average total length of 7.17 ± 0.22 cm, were reared for eight weeks using a recirculating system to determine the dietary protein requirement for their growth and survival. The effect of five experimental diets containing 40, 45, 50, 55 and 60% total protein content and two salinities (brackish water, BW at 5 UPS and marine water, MW at 36 UPS) were assessed. Fish were fed five times per day at 2.5% of total biomass. All treatments were performed in triplicate, recording the individual weight and total length every 15 d, while weight gain and daily growth rate were recorded at the end of the experiment. Mean weight increased proportionally as protein content increased, with the greatest growth occurring with a 60% protein diet for fish reared in brackish water, and 55% for fish in marine water. We consider that the protein requirement in C. undecimalis juveniles is high; in addition, it differs depending on the salinity, which may be due to the higher energy expenditure derived from the processes of osmoregulation in fish reared in marine water.

RESUMEN. Un total de 300 juveniles de Centropomus undecimalis con peso inicial promedio de 3.16 ± 0.28 g y longitud de 7.17 ± 0.22 cm se cultivaron por ocho semanas en un sistema de recirculación, con el objetivo de determinar el requerimiento de proteína dietaría en el crecimiento y supervivencia de los juveniles de C. undecimalis. El experimento consideró los niveles de proteína de 40, 45, 50, 55 y 60% en agua salobre, AS a 5 UPS y agua marina, AM a 36 UPS. Los peces se alimentaron cinco veces al día con una ración del 2.5% de biomasa. Los tratamientos se realizaron por triplicado, registrándose el peso individual y la longitud total cada 15 d, mientras que la ganancia en peso y la tasa de crecimiento diario se registró al final del experimento. El peso promedio incrementó con relación al aumento de la proteína, siendo mayor el crecimiento en los peces alimentados con 60% de proteína en agua salobre y con 55% de proteína para los peces cultivados en agua marina. El requerimiento de proteína en el cultivo de juveniles de C. undecimalis es alto, además de diferir en función a la salinidad, lo que puede deberse al mayor gasto energético derivado de los procesos de osmorregulación, de los peces cultivados con agua marina.

Abstract Background. Several studies have addressed the characterization of various digestive enzymes, which is essential to understanding the types, modes of action, and level of activity of these enzymes. Goals: The partial characterization of the digestive proteases was studied in fat snook juveniles (Centropomus parallelus, Poey 1869). Methods: Characterization was performed using electrophoretic and biochemical techniques. Results: Acidic proteases activity (stomach) is higher than alkaline proteases activity (intestine); also, chymotrypsin activity was superior to the trypsin activity. The optimal pH was 2 for stomach proteases with high stability in a wide range of pH 2-8, while the intestinal proteases showed two peaks with activity at pH 8 and 10 with stability at a pH of 8-12. Optimal temperatures were obtained between 45 to 55 °C for stomach and intestine proteases, respectively. Using proteases inhibitors, the presence of an aspartic protease (pepsin) was tested from stomach extracts and diverse serine proteases from intestine extracts. The zymograms showed 5 bands with alkaline proteolytic activity (79.5, 48.9, 37.0, 29.0, and 22.5 kDa), which were highly inhibited with PMSF, SBT1, and ovalbumin. Conclusions. C. parallelus is considered to have a high digestive capacity similar to those reported for other strictly carnivorous marine fish.

Resumen Antecedentes: Diversos estudios han abordado la caracterización de las diversas enzimas digestivas, lo cual es esencial para entender los tipos, modos de acción y nivel de actividad de dichas enzimas. Objetivos. La caracterización parcial de las proteasas digestivas se estudió en juveniles del chucumite (Centropomus parallelus, Poey 1869). Métodos: Se utilizaron técnicas bioquímicas y electroforéticas para la caracterización de proteasas. Resultados: La actividad de proteasas ácidas (estomacales) fue mayor a las proteasas alcalinas (intestinales). Asimismo, la actividad de la quimotripsina fue superior a la actividad de la tripsina. El pH óptimo para las proteasas estomacales fue de 2 con una alta estabilidad en el rango de pH 2-8, mientras que las proteasas intestinales mostraron dos picos con actividad a pH 8 y 10, siendo altamente estables a los pH 8 y 12. Las temperaturas óptimas se obtuvieron a 45 y 55 °C para proteasa estomacales e intestinales, respectivamente. Mediante el uso de inhibidores de proteasas se comprobó la presencia de pepsina en los extractos estomacales y de diversas serinas proteasas en los extractos intestinales. Los zimogramas mostraron cinco bandas con actividad proteolítica alcalina (79.5, 48.9, 37.0, 29.0 y 22.5 kDa), las cuales fueron fuertemente inhibidas con PMSF, SBT1 y ovoalbúmina. Conclusiones: Por lo anterior, se considera que C. parallelus tiene una alta capacidad digestiva similar a otros peces marinos carnívoros estrictos.

The horizontal and vertical distribution and the dorsal mantle length (DML) of the jumbo squid (Dosidicus gigas) were investigated in the Gulf of California (26-33 °N) during March and September-October 2010 using a Simrad EY-60 echo-sounder (120 kHz split beam transducer) and jig sampling. During March jumbo squids were captured and echo-detected off Santa Rosalía and around and south of the Grandes Islas region, in regions where satellite sea surface temperatures ranged between 16.5 and 18 °C. Jumbo squid were also abundant south of Guaymas Basin and along the east coast with SST ranged between 17.5 and 19 °C. During September-October jumbo squids were echo detected and captured at the west coast of the gulf at regions with SST below the mean of the survey area (< 30.5 °C). Jumbo squid distribution and DML estimated using hydroacoustic methods and measured from captured squids followed the previously known seasonal migrations and temporal DML frequency distribution reported in the Gulf, in the Grandes Islas region and east coast of the Gulf during the spring and in the east coast during late summer. Hydroacoustic data showed no evident daily vertical migrations during the two sampling seasons.

Se estudió la distribución horizontal y vertical y la estructura de longitud del manto (LM) del calamar gigante (Dosidicus gigas) recolectados en el Golfo de California (26 °-33 °N) durante marzo y septiembre-octubre del 2010, mediante una prospección acústica (ecosonda Simrad EY-60; 120 kHz de frecuencia, de haz dividido) y captura de calamares con poteras. Durante marzo, los calamares fueron eco detectados y capturados con poteras en la zona de las Grandes Islas, donde la temperatura superficial (TSM) detectada por satélite, registró un intervalo entre 16.5 y 18 °C. Los calamares fueron abundantes además al sur de la Cuenca de Guaymas y a lo largo de la costa este del golfo, en aguas con TSM entre 17.5 y 19 °C. Durante septiembre-octubre los calamares fueron eco detectados y capturados a lo largo de la costa oeste del golfo, en regiones con TSM por debajo de la media del área muestreada (<30.5 °C). La distribución horizontal y las estimaciones de LM realizadas con métodos de hidroacústica y capturados con poteras, concuerdan con los modelos de migración estacional y de distribución de frecuencias de LM previamente reportados en el golfo: principalmente distribuidos en las Grandes Islas y costa este del golfo en primavera, y en la costa este durante el final del verano. Los datos hidroacústicos no mostraron evidencia de migración vertical diaria en ninguna de las dos épocas del año estudiadas.

In the jumbo squid Dosidicus gigas has been reported a high incidence of cannibalism. The majority of the stomachs reviewed for determining squid diet have been obtained from fishery areas, therefore cannibalism in squids may be overestimated. In this study, a total of 236 Dosidicus gigas stomach contents were analyzed, these were taken from both fishing and non-fishing areas in the Gulf of California and San Carlos (west coast of the Baja California Peninsula) onboard seven cruises carried out between 2005 and 2010. Stomachs were analyzed following the standard methodology and the remains of squid (mantle pieces, suckers, beaks and eye lenses) were separated and weighted and that was called cannibalism weight (% W). Squid mantle length varied from 7 to 86 cm. Bigger sizes were found in fishing areas where cannibalism had major values of cannibalism. The cannibalism weight percentage (%W) and total weight of stomach content (TW) was high in fishing areas, but no significant difference in the frequency of occurrence (%FO) between areas and sex where found. Females presented a higher value of %W than males. The largest sizes had a greater %FO. Results suggest that fishery activities have an important influence in the cannibalism behavior on Dosidicus gigas, therefore this bias should be considered in diet studies when samples are taken from areas where fishing occurs.

En el calamar gigante Dosidicus gigas se ha reportado una alta incidencia de canibalismo. En general, la mayoría de los estómagos que se han revisado para determinar su dieta, provienen de áreas donde se realiza la pesca, lo que probablemente esté influyendo en una sobreestimación del canibalismo en los calamares. En el presente estudio, se analizaron un total de 236 contenidos estomacales de Dosidicus gigas, los cuales fueron recolectados tanto en áreas de pesca como de no pesca en el Golfo de California y costa occidental de la península de Baja California, a bordo de siete cruceros realizados entre 2005-2010. Los estómagos se analizaron siguiendo la metodología estándar y los restos de calamar (pedazos de manto, ventosas, picos y lentes oculares) fueron separados y pesados lo que se denominó peso del canibalismo (% W). La longitud de manto de los calamares varió entre 7-86 cm. Las tallas más grandes se encontraron en las zonas de pesca, donde el canibalismo fue mayor. En las áreas de pesca la proporción del peso del canibalismo (%W) y el peso total del contenido estomacal (TW) fueron mayores que en las zonas de no pesca, pero no hubo diferencia significativas en el porcentaje de frecuencia de ocurrencia de canibalismo (%FO) entre zonas y tampoco entre sexos, aunque las hembras mostraron un mayor %W que los machos. Las tallas mayores presentaron una mayor %FO. Los resultados sugieren que las actividades pesqueras, tienen una gran influencia en el comportamiento caníbal de la especie, por lo que debe considerarse este sesgo en las muestras provenientes de sitios en donde ocurre la pesca.