ABSTRACT The present study aimed to test the effect of three stocking densities: 100, 200, and 300 ind m-3 (D100, D200, and D300, respectively) on survival, growth (weight and total length), and condition factor of Microphis brachyurus. At the end of the six-week trial, there were no significant differences in the fish's survival, growth, and condition. The results suggest that this species presents high adaptability under culture conditions. A suboptimal stocking density generates a suboptimal use of infrastructure and decreases the production system's profitability. Based on the present study, a stocking density of 300 ind m-3 is recommended to increase the aquaculture infrastructure's profitability for ornamental or conservation purposes.

ABSTRACT In order to provide information on the current knowledge about the native fish Dormitator latifrons and identify the gaps that must be filled to achieve correct resource management, a scientometric study was carried out using different scientific databases. A total of 103 publications were registered between the years 1972 and 2021. Results indicate that the species has been addressed since 2001 with less than one publication per year, with 2008 being the year with the highest number of publications (10). The main topics addressed were ecology, physiology, and parasitology of fish. The available knowledge generated about the species is concentrated in 68 journals, with Mexico as the most productive country, followed by USA and Ecuador, and the most productive research centers about this fish were Mexico’s Instituto Politécnico Nacional and Universidad de Guadalajara. A total of 285 authors were detected contributing knowledge to the species, with Violante-González in the top with ten publications. The co-authorship co-occurrence maps suggest there is no solid collaborative relationship between the scientific community and that the information generated is insufficient for conserving and exploiting this fish. It is essential to increase the study of thematic areas that allow their comprehensive management in the medium term; topics like reproduction in captivity, aquaculture, and nutrition must be addressed in the future to assure a sustainable use of this resource.

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. 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 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 Totoaba macdonaldi is an endemic species which has been overexploited causing its population to decrease and to be cataloged as endangered. Understanding the larval period is the most critical stage in the development of marine fish farming. Our study aims to determine the changes in digestive enzyme activities during the early ontogeny of totoaba, using biochemical and electrophoretic techniques as SDS-PAGE. The results show that the acid protease had maximum activity between days 28 and 32 days post-hatching (DPH) when the Artemia was replaced by formulated food. Alkaline protease activity was detected at 2 DPH with maximal activity between 20 and 32 DPH; trypsin activity became active from 2 DPH; chymotrypsin activity increased at 6 DPH; leucine aminopeptidase activity was detected at 3 DPH, showing its maximal level at 22 DPH; carboxypeptidase A activity increased at 3 DPH; and lipase and amylase activities were detected at 2 DPH. Acid zymogram showed only one isoform (0.72 rf) from 2 DPH and increased in intensity from 8 DPH. For alkaline proteases, four isoforms were detected from yolk absorption (1 DPH), increasing to six isoforms (77.8, 47.3, 43.5, 21.0, 19.2, and 17.5 kDa) from 8 DPH onwards. Our results demonstrate that larvae of T. macdonaldi present characteristics typical of carnivore marine fish, showing the presence of alkaline digestive enzymes prematurely and the presence of offset pepsin. According to the results obtained in the present study, T. macdonaldi can be a juvenile beginning between 24 and 28 DPH, being the most appropriate day to perform replacement by artificial food.

Abstract The study evaluated the influence of age (30, 60, 90 and 120 days) on dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), free condensed tannins (FCT), fiber-bound condensed tannins (FBCT), protein-bound condensed tannin content (PBCT), in vitro degradation rate of DM (DMkd), CP (CPkd) and NDF (NDFkd) of Morus alba (MA) and Hibiscus rosa-sinensis (HRS). For MA leaves, there was a quadratic (p < 0.01) relationship between CP content and age: the CP content of 60, 90 and 120 days-old leaves was similar, but it was lower than that of 30 days-old leaves. For HRS leaves, CP content decreased linearly (p < 0.01) as age increased, and NDF content increased linearly (p < 0.01). For both MA and HRS, there were cubit (p < 0.01) effects of age on FCT, FBCT and PBCT content, in which the highest values were found in 120-d-old leaves and the lowest in 30 and 90 d-old leaves. Furthermore, old leaves had a linear decrease in DMkd, CPkd, and NDFkd. DMkd, CPkd, and NDFkd negatively correlated (p < 0.001) with FCT, FBCT, and PBCT content. For both MA and HRS, 90 days-old leaves had higher nutritional value than 120 days-old leaves.

Resumen En el estudio se evaluó la influencia de la edad (30, 60, y 120 días) de la materia seca (MS), proteína cruda (PC), fibra detergente neutro (FDN), taninos condensados libres (TCL), taninos condensados ligados a la fibra (TCFB), contenido de taninos condensados ligados a proteínas (TCPB), velocidad de degradación in vitro de la MS (VDkd), PC (PCkd) y FDN (FDNkd) de Morus alba (MA) e Hibiscus rosa-sinensis (HRS). Para las hojas de MA, hubo una relación cuadrática (p < 0.01) entre el contenido de PC y la edad: el contenido de PC de las hojas de 60, 90 y 120 días fue similar, pero menor que el de las hojas de 30 días. Para las hojas de HRS, el contenido de PC disminuyó linealmente (p < 0.01) a medida que aumentaba la edad, y el contenido de FND aumentó linealmente (p < 0.01). Tanto para MA como para HRS hubo efectos cúbicos (p < 0.01) en la edad sobre el contenido de TCL, TCFB y TCPB, en los cuales los valores más altos se encontraron en hojas de 120 días y las más bajas en hojas de 30 y 90 días. Además, las hojas viejas tuvieron una disminución lineal en MSkd, PCkd y FDNkd. MSkd, PCkd y FDNkd se correlacionaron negativamente (p < 0.001) con el contenido de TCL, TCFB y TCPB. Tanto para MA como para HRS, las hojas de 90 días tuvieron un valor nutricional mayor que las hojas de 120 días.

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 Digestive proteases were partially characterized in sheepshead juveniles, using biochemical and electrophoretic techniques. Results showed higher activity level of the stomach proteases (2.39 ± 0.02 U mg protein-1) compared to the intestinal proteases (1.6 ± 0.1 U mg protein-1). The activity of trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A was also recorded. The optimum temperature of the stomach proteases was recorded at 45 °C, while for intestinal proteases was recorded at 55 °C. Stomach proteases showed less stability to temperature changes than intestinal proteases. An optimum pH of 2 was recorded for stomach proteases with high stability under acidic conditions, while an optimum pH of 9 was recorded for intestinal proteases showing high stability under alkaline conditions. Stomach proteases were inhibited around 78% with Pepstatin A, indicating the presence of pepsin as the main protease. The stomach proteases zymogam revealed one active band with Rf of 0.49, this enzyme was completely inhibited by Pepstatin A. The intestinal proteases zymogram revealed four active proteases (51.3, 34.9, 27.8 and 21.2 kDa) that were inhibited by TLCK, which mainly represent a trypsin-like serine proteases. It can be conclude that digestion in sheepshead can be considered as a carnivorous species with an omnivorous tendency.

RESUMEN Se caracterizaron parcialmente las proteasas digestivas de juveniles del sargo, utilizando técnicas bioquímicas y electroforéticas. Los resultados muestran mayores niveles de actividad en las proteasas estomacales (2.39 ± 0.02 U mg proteina-1) comparados con los de las proteasas intestinales (1.6 ± 0.1 U mg protein-1), también se registró la actividad de tripsina, quimotripsina, leucina aminopeptidasa y carboxipeptidasa A. La temperatura óptima de las proteasas estomacales fue de 45 °C, mientras que la de las proteasas intestinales fue de 55 °C. El pH óptimo fue de 2 para las proteasas estomacales con alta estabilidad a condiciones ácidas, mientras que el pH óptimo para las proteasas intestinales fue de 9, mostrando una alta estabilidad en condiciones alcalinas. Las actividades de las proteasas estomacales fue inhibida en un 78% con Pepstatina A, lo que indica la presencia de pepsina, como principal proteasa. El zimograma de proteasas estomacales reveló una sola banda con actividad proteasa, con Rf de 0.49, completamente inhibida por Pepstatina A. El zimograma de proteasas intestinales reveló cuatro bandas (51.3, 34.9, 27.8 y 21.2 kDa). Todas las bandas se inhibieron con TLCK, lo que muestra la presencia principalmente de serina proteasas tipo tripsina. Se concluye que la digestión del sargo puede ser considerada como la de una especie carnívora con tendencia al omnivorismo.

The effect of dietary protein (31, 41, 45, and 55%) was evaluated in quadruplicate in the yellow snapper (Lutjanus argentiventris). Specimens were kept in sixteen 200 L plastic tanks for 95 days and the values of growth rate, feeding efficiency and proximate composition of yellow snapper (18 g) were examined. Every 15 days were carried out individual weight measurements and standard length of the total population. At the beginning and end of the experiment, liver and muscle samples were taken for proximate analysis of crude protein and ether extract. In general, the highest gain was obtained with fish fed with 55% crude protein in the diet. The best feed conversion ratio (FCR), specific growth rate (SGR), percent weight gain (WG%), average daily gain (ADG), and feed efficiency rate (FER) were obtained with the fish fed 55% of protein (CP). The protein content in liver decreased in fish fed with protein levels and higher energy compared with the initial fish. Finally, the use of practical diets containing 55% CP is appropriate for optimal growth and efficiency of feed utilization of yellow snapper. The results obtained in this study may be due to the early stage of development of yellow snapper where protein and energy requirements are higher.

El efecto de diferentes niveles de proteína en la dieta (31, 41, 45 y 55%) fue evaluado por cuadruplicado en el pargo amarillo Lutjanus argentiventris. Los organismos fueron mantenidos en 16 tanques de plástico de 200 L por 95 días y los valores de crecimiento, eficiencia alimenticia y composición proximal del pargo amarillo (18 g) fueron examinados. Cada 15 días se llevaron a cabo mediciones de peso individual y longitud estándar del total de la población. Al inicio y al final del experimento, muestras de hígado y músculo fueron tomadas para análisis proximal de proteína cruda y extracto etéreo. En general, la ganancia de peso más alta fue obtenida con los peces alimentados con 55% de proteína. La mejor tasa de conversión alimenticia (FCR), tasa de crecimiento específico (SGR), porcentaje de ganancia de peso (WG%), ganancia diaria promedio (ADG) y tasa de eficiencia alimenticia (FER) se obtuvo con los niveles más altos de proteína cruda. El contenido de proteína en hígado disminuyó en los peces alimentados con los niveles de proteína y energía más altos comparados con el pez inicial. Finalmente, el uso de dietas prácticas conteniendo 55% de proteína cruda es apropiado para un óptimo crecimiento y eficiencia en la utilización del alimento del pargo amarillo. El resultado obtenido en este estudio puede ser debido a la fase temprana de desarrollo del pargo amarillo, donde los requerimientos de proteína y energía son más elevados.

El género Procambarus ha recibido mayor atención en los estudios de los principios fundamentales de su biología debido a su diversidad en el territorio mexicano y potencial uso en acuicultura. El cariotipo típico del acocil tropical mexicano Procambarus (Austrocambarus) llamasi, se estudió mediante 189 dispersiones cromosómicas en metafase del tejido branquial de 17 adultos tratados con la técnica citológica de inmersión. Encontramos un amplio número de cromosomas, que variaron entre 98-120 elementos cromosómicos, con número modal diploide de 2n=120 elementos cromosómicos. El cariotipo del acocil tropical esta constituido por 60 pares de cromosomas monorrámeos, todos los centrómero están en la región telocéntrica de los cromosomas. En las metafases mitóticas de hembras y machos no fueron identificados cromosomas sexuales. Sugerimos considerar la estructura cromosómica del cariotipo como una herramienta citotaxonómica así como el empleo de datos cariológicos para propósitos de acuicultura y conservación del acocil tropical.

In Mexico, the biology of Procambarus has been more studied than the biology of other Cambarids because of its diversity and potential use in aquaculture. We determined the karyotype of the Mexican tropical freshwater crayfish Procambarus (Austrocambarus) llamasi from 189 metaphase spreads from gill tissues of 17 adults. They had 98-120 chromosomes (mode 2n=120 chromosomes). There are 60 pairs of monoarm, telocentric chromosomes. Sex chromosomes were not detected and we propose that the P. llamasi karyotype can be used to distinguish this species from other Mexican crayfish. Additionally, we suggest using karyological data in aquaculture and conservation biology. Rev. Biol. Trop. 58 (2): 655-662. Epub 2010 June 02.

El cariotipo del pejelagarto Atractosteus tropicus se describe por medio de tinción Giemsa de 295 preparaciones cromosómicas en mitosis a partir de 120 larvas y 15 adultos (5 hembras y diez machos) de la población que habita en Tabasco, sureste de México. El número diploide 2n=56 cromosomas se dio en 281 dispersiones cromosómicas de un total de 445 muestras, de ellas 73 dispersiones provinieron de 206 metafases larvales, y 208 dispersiones de 239 metafases de adultos. Se observó variación en el número de cromosomas desde 46 hasta 64 elementos cromosómicos (larvas). Las metafases con 58 cromosomas fueron el segundo valor más abundante, después del número diploide 2n=56 (35%). En los adultos esa variación no fue relevante. Esta variación cromosómica se relaciona con microcromosomas móviles. El cariotipo se determinó de seis dispersiones cromosómicas bien definidas de tres hembras y tres machos; y el cariotipo promedio se integró de ocho pares de cromosomas metacéntricos (m), cuatro pares de cromosomas submetacéntricos (sm), ocho pares de telocéntricos (t), y ocho pares de microcromosomas telocéntricos (*t) El número fundamental observado en el cariotipo típico promedio fue NF = 80 brazos cromosómicos. No se detectaron diferencias sexuales.

Karyotype of the tropical gar Atractosteus tropicus Lepisosteiformes: Lepisosteidae) and chromosomal variation in their larval and adults. The karyotype of the tropical gar Atractosteus tropicus is described from conventional Giemsa-staining of 295 mitotic chromosome slides from 120 larvae and 15 adults (five females and ten males) from Tabasco, southern of Mexico. The diploid number 2n = 56 chromosomes was calculated (73 spreads from 206 larval and 208 adult metaphases). Variation on chromosome number was from 46 (4.4%) to 64 (3.9%) chromosome elements on larval samples, whereas 58 (11.7 %) chromosomes were the second most abundant after the diploid number of 2n = 56 (35%). Such variation was related with the presence of mobile microchromosomes. The karyotype was determined from six clear chromosome spreads photographed from three females and three males. The averaged karyotype was integrated by eight pairs of metacentric (m) chromosomes, four submetacentric (sm) pairs, eight telocentric (t) pairs and eight pairs of telocentric micro-chromosomes (*t). The fundamental number was FN = 80 chromosome arms. We saw no sexual differences on chromosome structure. Rev. Biol. Trop. 57 (3): 529-539. Epub 2009 September 30.