The Orinoco Striped Catfish Pseudoplatystoma orinocoense is a highly valued commercial‐capture species in Colombia. Although this species was considered endangered and is now in a recovery situation, there are still no cryopreservation studies for its milt. Therefore, the objective of this study was to evaluate the effects of different cryopreservation media and two packaging systems on the sperm motility and fertilization capacity of Striped Catfish. A first experiment was conducted to test the effects of two permeating cryoprotectants (10% dimethyl sulfoxide and 12% methanol) combined with glucose at two concentrations (5.5% and 10%) and with two membrane stabilizers (12% egg yolk and 5% whole milk powder) on the post‐thaw motility of milt samples that were packed into 0.5‐mL straws. The cryopreservation media with the best results in the first experiment were selected for a second experiment in which we evaluated 5‐mL macrotubes as a packaging system. In this case, the response variables were sperm motility and fertility rate. In both experiments, milt with sperm motility that exceeded 90% was diluted at a 1:6 (volume basis) ratio in each of the two cryopreservation media. The diluted samples were packed, equilibrated (for 10 min), then frozen in a nitrogen‐vapor dry shipper for 30 min, and finally stored in liquid nitrogen until they were evaluated. Each factor and its interactions showed a significant effect (P < 0.001) on post‐thaw sperm motility in experiment 1. The best protection during cryopreservation was obtained when 12% methanol supplemented with 5.5% glucose was used as a permeating cryoprotectant, yielding an average motility of 33.3 ± 5.1% (mean ± SD) and 64 ± 5.4% in the 0.5‐ and 5‐mL packaging systems, respectively. Similarly, the highest fertility rate (85%) was recorded under this treatment, with no significant difference (P > 0.05) from the fresh milt. Therefore, Striped Catfish milt can be cryopreserved in 5‐mL macrotubes by using 12% methanol and 5.5% glucose, without the addition of membrane stabilizers.
El 17α-etinilestradiol (EE2) es un esteroide sintético que interfiere en el sistema endócrino reproductivo de los peces. En este estudio se evaluó el efecto del EE2 como posible perturbador endócrino en hembras y en machos adultos de Aequidens metae expuestos a 0.5, 5, 50 y 250 ng/L por 21 días. Se incluyó un testigo negativo (C) y un testigo con solvente (etanol) (CE). Finalizada la exposición al EE2, la sangre fue colectada para determinar calcio y fósforo plasmático y en las gónadas e hígado se evaluaron los índices somáticos y las alteraciones histológicas. Los índices gonadosomático y hepatosomático no presentaron diferencias significativas. A nivel histológico, en los ovarios se encontró congestión, fibrosis intersticial, apoptosis, atresia y material vitelogénico. A nivel testicular, se observó acumulación de material de melanomacrófagos, degeneración testicular, fibrosis intersticial, atrofia y engrosamiento de la pared intersticial. Y en hígado, en ambos sexos, se observó mayor picnosis degenerativa, activación de macrófagos, apoptosis, infiltraciones, dilatación y congestión, en comparación con los grupos testigo. Las hembras no presentaron diferencias significativas en calcio y fósforo plasmático. Los machos expuestos a las tres concentraciones más altas tuvieron valores significativamente mayores en el calcio plasmático en comparación con el grupo testigo. Con respecto al fósforo plasmático, en los machos expuestos a 250 ng/L se presentaron diferencias en comparación con el grupo testigo. Estos resultados permiten inferir que esta especie es sensible a los efectos de la perturbación endocrina generados por el EE2, y que la determinación de parámetros bioquímicos como los iones de calcio y fósforo pueden ser usados como biomarcadores adicionales del estado de salud de los peces expuestos a xenobióticos.
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