RESUMODeterminou-se a dose inseminante para fertilização artificial e descreveu-se o desenvolvimento embrionário de tambaqui (Colossoma macropomum). Os gametas foram coletados de reprodutores induzidos hormonalmente. Foi realizada fertilização artificial nas proporções de espermatozoides/ovócito de D1-50.666; D2-75.999; D3-101.332; D4-126.665; D5-151.998. O desenvolvimento embrionário foi acompanhado por meio de observações periódicas em estereoscópio até a eclosão dos ovos. Na fase de fechamento do blastóporo foi calculada a taxa de fertilização nas diferentes doses inseminantes. A porcentagem de fertilização aumentou de forma linear segundo a equação Ŷ =0,050 + 0,00000773X (R 2 =97,5), atingindo um platô em 84% na proporção de 102.486 espermatozoides/ovócito. Os embriões apresentaram segmentação meroblástica discoidal, típica de ovos telolécitos, com eclosão ocorrendo aos 357 horas-grau após a fertilização. Conclui-se que o desenvolvimento embrionário de tambaqui obedece ao esperado para peixes com ovos telolécitos e recomenda-se o uso da dose inseminante de aproximadamente 100.000 espermatozoides/ovócito na rotina de fertilização artificial dessa espécie.Palavras-chave: tambaqui, embriologia, espermatozoides/ovócito, reprodução D1-50666, D2-75999, D3-101 332, 126 665-D4, D5-151 ABSTRACT The objective of this research was to determine the insemination dose for artificial fertilization and describe the embryonic development of tambaqui (Colossoma macropomun). The gametes were collected from induced breeding hormonally. An artificial fertilization was performed with different sperm/oocyte ratios of

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Tambaqui (Colossoma macropomum) is a native freshwater fish that is of great importance for Brazilian aquaculture. Because of this importance, several techniques have been developed to improve the reproduction of this species in captivity. One of these techniques is the cryopreservation of sperm. In an effort to increase the efficiency of cryopreservation protocols, researchers have tried to determine suitable diluting solutions and freezing methods, which will provide a better post-thaw sperm quality. Thus, this study aimed to evaluate the efficiency of different diluents and freezing methods for the cryopreservation of tambaqui (C. macropomum) sperm. Samples of fresh semen were diluted in different treatments (Glucose 5% + 10% Dimethyl sulfoxide -DMSO, Glucose 5% + 10% Methyl glycol -MG, BTS + 10% DMSO and BTS + 10% MG) at a 1:9 dilution rate and frozen in a programmed freezing machine and a dry shipper. The semen samples were thawed and evaluated for vitality, sperm morphology and kinetics. Cryopreserved semen with DMSO and using the programmed freezing machine provided a greater percentage of motile sperm (15.44 ± 1.04%) after thawing compared to the dry shipper (3.99 ± 0.55%), regardless of the diluent. Additionally, DMSO showed better sperm velocities than MG regardless of the freezing method and the extender employed. A higher percentage of living spermatozoa was observed when glucose (37.28 ± 1.32%) (regardless of the freezing method and cryoprotectant) and DMSO (37.98 ± 1.25%) was used in the programmed freezing machine. For morphology, a greater amount of normal spermatozoa (46.10 ± 1.82%) was observed when the semen was cryopreserved using a freezing machine programmed with DMSO as the cryoprotectant and Glucose or BTS (38.16 ± 1.9% and 39.26 ± 1.87%, respectively) as extenders. Therefore, we suggest the use of the DMSO (10%) cryoprotectant in association with the Glucose (5%) extended in the programmed freezing machine for cryopreservation of C. macropomum semen. ResumoO tambaqui (Colossoma macropomum) é uma espécie nativa de peixe de água doce de grande importância para aquicultura brasileira. Devido a isso, diversas técnicas têm sido desenvolvidas para aperfeiçoar a reprodução desta espécie em cativeiro, dentre elas a criopreservação de sêmen de peixe. Como uma forma de melhorar os protocolos de criopreservação, tem-se buscado utilizar soluções diluidoras e métodos de congelação adequados, proporcionando uma boa qualidade seminal pós-descongelação. Dessa forma, este estudo objetivou avaliar a eficiência de diferentes diluidores e métodos de congelação na criopreservação do sêmen de tambaqui (C. macropomum). As amostras de sêmen fresco foram diluídas em diferentes tratamentos (Glicose 5% + 10% Dimetilsufóxido -DMSO; Glicose 5% + 10% Metil glicol -MG; Beltsville Thawing Solution -BTS + 10% DMSO e BTS + 10% MG) na proporção 1:9 e congeladas em máquina de congelação programada e em Dry shipper. As amostras seminais foram descongeladas e avaliadas para vitalidade, morfologia e cinética espermát...

This study evaluated the effect of glucose or Beltsville Thawing Solution (BTS™) combined with dimethyl sulfoxide (DMSO) or methylglycol (MG) under two different freezing protocols on the kinetics and morphology of cryopreserved Prochilodus brevis sperm. The semen samples were diluted using one of four different treatments (glucose+DMSO, glucose+MG, BTS™+DMSO, and BTS™+MG), loaded into 0.25-ml straws and subjected to two different freezing processes (programmed freezing machine and dry shipper). After 10 days, the semen samples were thawed, and the sperm morphology and kinetics were evaluated. The physicochemical parameters of the semen in natura were similar to those observed in other studies of Characiformes, indicating the feasibility of semen cryopreservation. Glucose, when used as a diluent with the cryoprotectant MG (glucose+MG), yielded higher percentages of mobile spermatozoa after freezing in a dry shipper (76.88 ± 4.84%) and in a programmed freezing machine (70.95 ± 1.76%) compared with the combination of glucose and DMSO. Moreover, the glucose+MG treatment yielded a higher sperm velocity (curvilinear velocity: 79.52 ± 2.88 µm s -1 ; straight-line velocity: 45.46 ± 3.01 µm s -1 ; average path velocity: 67.92 ± 3.08 µm s -1 ) than the other studied treatments, and a higher amount of normal sperm (74.56 ± 0.77%) was observed in the semen samples cryopreserved using a programmed freezing machine. The sperm abnormalities observed included a bent tail morphology. Therefore, the use of glucose+MG in combination with either a dry shipper or a programmed freezing machine is recommended for the cryopreservation of P. brevis sperm because these methods yielded high numbers of motile and morphologically normal spermatozoa.

Chemical pollution is one of the major threats to global freshwater biodiversity and will be exacerbated through changes in temperature and rainfall patterns, acid–base chemistry, and reduced freshwater availability due to climate change. In this review we show how physico‐chemical features of natural fresh waters, including pH, temperature, oxygen, carbon dioxide, divalent cations, anions, carbonate alkalinity, salinity and dissolved organic matter, can affect the environmental risk to aquatic wildlife of pollutant chemicals. We evidence how these features of freshwater physico‐chemistry directly and/or indirectly affect the solubility, speciation, bioavailability and uptake of chemicals [including via alterations in the trans‐epithelial electric potential (TEP) across the gills or skin] as well as the internal physiology/biochemistry of the organisms, and hence ultimately toxicity. We also show how toxicity can vary with species and ontogeny. We use a new database of global freshwater chemistry (GLORICH) to demonstrate the huge variability (often >1000‐fold) for these physico‐chemical variables in natural fresh waters, and hence their importance to ecotoxicology. We emphasise that a better understanding of chemical toxicity and more accurate environmental risk assessment requires greater consideration of the natural water physico‐chemistry in which the organisms we seek to protect live.

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