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The effects of straws volume, cryoprotectants and thawing temperatures were evaluated on the sperm quality of cachama blanca Piaractus brachypomus (Cuvier), an important Colombian fish species. Sexually mature fish were induced to ovulation or spermiation with a carp pituitary extract. A pool of suitable sperm samples was diluted in glucose, egg yolk, dimethyl sulphoxide (DMSO‐10%), methanol (MET‐10%) or ethylene glycol (ETG‐5%) and packed in 0.5, 2.5 or 5.0 mL straws and frozen in nitrogen vapour. The thawing process was performed in a 35 or an 80 °C water bath. The fertility was evaluated after 6 h post fertilization. The highest motility percentage (33 ± 3%) was observed with sperm cryopreserved with DMSO, packed in 5 mL straws and thawed at 35 °C. The treatments with DMSO and MET packed in 0.5 and 5.0 mL straws and thawed at 35 °C showed the highest fertility (higher than 71%) and the lowest fertility was obtained with MET‐2.5 mL (9 ± 5%). In all the treatments, a significant decrease in the sperm quality was observed at 80 °C. Sperm cryopreserved with DMSO‐10% or MET‐10%, packed in 2.5 or 5.0 mL straws are suitable to achieve acceptable fertilization and to fertilize high amounts of eggs.

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In Colombia and the rest of the world, the decrease in capture fisheries production has turned the aquaculture into an alternative source of protein for the populations food security as well as an important productive activity, generating employment and income for the rural communities. The Colombian pisciculture is based on red Tilapia Oreochromis sp. (Linnaeus), Rainbow trout Oncorhynchus mykiss (Walbaum) and cachama blanca Piaractus brachypomus (Cuvier), which currently represent around 96% of the total national production. The remaining 4% comes from other farmed species such as bocachico Prochilodus magdalenae (Steindachner), carp Cyprinus carpio (Linnaeus) and yamúBrycon amazonicus (Spix & Agassiz). From the three main fish species, cachama blanca is the only native species, which has shown excellent performance in pond farming due to its rusticity, omnivorous habits, docility, meat quality, food conversion and disease resistance. The limited offer of Colombian fish farmed species determines its currently low competitiveness and restricted impact on the international markets; thus making necessary to explore the potential of new fish species in order to introduce them to the pisciculture system and to expand the range of fish farming species. A good alternative is the introduction of native catfish, which have great potential for fish farming activity.

SUMMARYThe aim of this study was to evaluate the freezing-thawing conditions of yamú (Brycon amazonicus) sperm packaged in straws of different volume and their effect on the spermatic motility and fertility post-thawing. The induction to gonadal final maturation was made with carp pituitary extract. The sperm obtained was evaluated and diluted (1:4) in a solution with 5.5% glucose, 12% egg yolk and 10% dimethyl sulfoxide, packaged in 0.5, 1.8, 2.5 or 4.0 ml straws and frozen in nitrogen vapors. The thawing was carried out in a 35ºC, 60ºC or 80ºC water bath during different times. All straws showed a similar overall freezing rate (7.5 to 12.9ºC min -1 ). On the other hand, the overall thawing rate was faster at a higher water bath temperature. The 4.0 ml straws thawed at 35ºC showed the highest motility and activation time post-thaw (47.0 ± 1.6% and 60.2 ± 2.4 sec). The fertility obtained with cryopreserved sperm in all straw sizes was significantly lower (P < 0.05) than with fresh sperm (65 ± 4%). The highest fertility was observed with 0.5 ml straw thawed at 35ºC (52 ± 3%), followed by 2.5, 4.0 and 1.8 ml straws (51 ± 3, 48 ± 3 and 47 ± 3%, respectively). It was concluded that 4.0 ml straws thawed at 35ºC showed the best post-thaw sperm quality and more homogenous freezing-thawing rates in comparison to the other packaging systems. On the other hand, no effects on fertility were observed in all straw sizes thawed at 35 ºC.Palabras clave: fertilidad, pajilla, semen, tasa de congelación-descongelación.

Osmolality, the concentrations of glucose, total cholesterol, and triglyceride, and the concentrations of ions such as Na+, Cl−, K+, and Mg2+ in the seminal plasma of yamú Brycon amazonicus were evaluated during one reproductive season. Semen quality and the relationship between spermatocrit and sperm concentration were examined over two reproductive seasons. Activation time, spermatocrit, and sperm concentration were significantly higher in 2003 than in 2004. Spermatocrit and sperm concentration showed a significant positive relationship (r 2 = 0.79). During the 2004 reproductive season, a significant variation was observed for spermatocrit and sperm concentration between the initial period (February 15th to March 14th) and the middle and final periods (March 15th to April 14th and April 15th to May 14th, respectively). Neither the ion concentrations nor the glucose and cholesterol concentrations varied between any periods of the reproductive season. Osmolality and triglyceride concentrations showed significant variations between periods during the reproductive season.

RESUMENObjetivo. Evaluar los efectos de diferentes tipos de alimentos sobre la productividad de Diaphanosoma sp., y Alona sp bajo condiciones de laboratorio. Materiales y métodos. Juveniles de Diaphanosoma sp., y Alona sp., fueron sembrados en acuarios de 20 L a una densidad de 6 org L-1 y mantenidos con aireación constante y fotoperíodo 12:12 (luz : oscuridad). Se alimentaron con Saccharomyces cereviseae y Chlorella vulgaris a concentración de 4 x 105 Cel/ml cada uno, en tres combinaciones: 1. C. vulgaris, 2. S. cereviseae, 3. C. vulgaris + S. cereviseae en proporciones iguales; de cada tratamiento se realizaron 3 réplicas. Con el propósito de determinar la densidad poblacional, cada 3 días y durante un período de 27 días, y se midió la concentración de individuos por ml. Resultados. Se obtuvieron mejores resultados en el tratamientos de microalgas + levadura, con valores de TCE=0.1323±0.07 y 0.1598±0.04 días-1; R=0.010 ±0.004 y 0.019±0.01 org ml-1 día-1, TD=5.2±0.5 y 4.3±0.38 días para Diaphanosoma sp., y Alona sp., respectivamente, pero sin presentar diferencias significativas (p>0.05). Conclusiones. La dieta mixta de levadura y microalgas produjo mayor eficiencia productiva en las dos especies estudiadas, constituyendo una alternativa de fuente de alimento vivo para la acuicultura

RESUMENObjetivo. Determinar la variación de la calidad, el contenido iónico y la osmolaridad del plasma seminal de Pseudoplatystoma metaense durante la estación reproductiva. Materiales y métodos. Se utilizaron machos sexualmente maduros durante un periodo reproductivo (marzo a agosto). La espermiación fue inducida con Extracto de Hipófisis de Carpa (4 mg/kg). Se evaluó el volumen (mL), movilidad masal (%), tiempo de activación (sg), espermatocrito (%); concentración espermática (10 6 sptz/µL) y viabilidad (%). También fue determinada la movilidad (%) y velocidad individual por medio de un Sistema de Análisis Espermático Asistido por Computador (CASA). La osmolaridad (mOsm/Kg) y la concentración de iones (Na + , Cl + , K + y Mg 2+ ) y glucosa fue determinada en plasma seminal obtenido por centrifugación del semen a 14.000 g. La concentración de iones y glucosa fue establecida a través de un sistema de reflectancia. Resultados. El semen de Pseudoplatystoma metaense presentó una movilidad masal mayor al 90%, con el menor valor de movilidad progresiva lineal rápida para el mes de abril (34.9±9.0%) y en general valores de espermatozoides inmóviles menores al 10%. El plasma seminal mostró una osmolaridad de 259.3± 3.5 mOsm/Kg, con una concentración promedio de glucosa e iones Na + , Cl + , K + y Mg 2+ de 142.7±2.8, 118±2.2, 4.8±0.4 y 0.33±0.0 mmol/L, respectivamente, durante la época reproductiva. Conclusiones. La calidad seminal de bagre rayado no presentó variaciones en la estación reproductiva mostrando una alta calidad para los procesos de fecundación.