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Reactive oxygen species (ROS) have been proposed as one of the main causes of the impairment of fish spermatozoa integrity and functionality during cryopreservation. The high content of unsaturated fatty acids in sperm cells and the low antioxidant capacity of diluted semen are key factors in making sperm cells susceptible to ROS attacks. For this reason, some recent studies have determined the antioxidant status of the seminal plasma and spermatozoa of fish species. Additionally, some studies have evaluated the effects of antioxidants on post-thaw sperm quality. Although ROS are certainly involved in sperm damage, other factors, such as ice crystal formation, seem to play a crucial role in cryodamage. This challenge has not yet been resolved because both the endogenous antioxidant capacity of the semen and its response to different supplementation practices seem to present specific inter-and intraspecies characteristics and effects. This review summarises knowledge on antioxidant defence and oxidative stress in fish semen, as well as antioxidant supplementation in cryopreservation media, in order to establish perspectives for future studies.

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La Cachama negra (Colossoma macropomum) es un pez nativo de Sur América. En Colombia, no hay estudios publicados sobre protocolos estandarizados para su crioconservación seminal. La implementación de esta biotecnología permitiría su producción comercial continua e introducción en bancos de recursos genéticos. El objetivo del presente estudio fue evaluar los efectos de la crioconservación sobre el semen de C. macropomum sometido a diferentes crioprotectores y sistemas de empaque con miras a consolidar un protocolo eficiente para la especie. Se utilizó semen de tres machos sexualmente maduros (4.6 ± 1.6 kg). El semen fue diluido en una proporción 1:4 usando tres diferentes agentes crioprotectores (Dimetilsulfoxido 10% [DMSO], Metanol 10% [MET], Etilenglicol 5% [ETG]) con o sin la inclusión de yema de huevo 12% (YH) y glucosa 5.5%. Además, fueron evaluados dos sistemas de empaque (pajillas de 0.5 ml y macrotubos de 2.0 ml), las cuales fueron expuestas a vapores de nitrógeno líquido (NL) y luego almacenadas durante 8 meses. El semen fue descongelado en baño de agua a 37°C por 60 s y se determinó la motilidad masal (%) [MM], duración de la motilidad (s) [DM], integridad de membrana plasmática (%) [IMP] y fertilidad (%). La motilidad postdescongelación en todos los tratamientos fue significativamente diferente (P<0,05) al control siendo MET 2.0 ml el mejor (53 ± 5.8%). Respecto al control la DM tuvo un comportamiento similar para todos los tratamientos siendo solo diferente significativamente para ETG+YH 0.5 ml. La IMP se mantuvo sin diferencias significativas en MET 2.0 ml con respecto al control. La fertilidad fue significativamente menor en la mayoría de tratamientos con YH, siendo MET 2.0 ml el mejor (94.7 ± 0.6%). En conclusión, el semen de Colossoma macropomum es susceptible de crioconservación no siendo necesaria la utilización de YH en los diluyentes.

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.

Estudios preliminares sobre congelación de embriones de yamú (Brycon amazonicus) en diferentes estadíos de desarrollo 225 ARTÍCULO ORIGINAL/ORIGINAL ARTICLE Estudios preliminares sobre congelación de embriones de yamú (Brycon amazonicus) en diferentes estadios de desarrollo Preliminary studies on embryo freezing of yamú (Brycon amazonicus) in different stages of development Estudos preliminares sobre congelamento de embriões do matrinxã (Brycon amazonicus) em diferentes estágios de desenvolvimento

Rapid environmental changes will be the major challenge that most biota will have to deal with in the near future. Extreme events, such as marine heatwaves, are becoming more frequent and could be spatially uniform at a regional scale for a relatively long period of time. To date, most research studies on heatwaves have focused on sessile organisms, but these extreme events can also impact mobile species. Here, a 3‐week marine heatwave was simulated to investigate its effects on the male reproductive performance of a Mediterranean Sea emblematic species, the European sea bass Dicentrarchus labrax. Males from the control condition (c. 13°C) produced significantly more sperm than those exposed to a relatively warm thermal treatment (c. 16°C). Nonetheless, neither the percentage of motile spermatozoa nor most of the other sperm motility parameters were significantly affected by the rearing temperature over the whole period. Overall, the results of this study suggest only moderated effects of a potential winter heatwave on the reproductive performance of male European sea bass.