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Cryopreservation has not been used successfully to preserve fish embryos, although chilling techniques have been used with good results. The aim of this study was to chill Piaractus brachypomus embryos at - 10°C for various storage times. Embryos at the following ontogenetic stages were used: blastoderm - 1.2 hours post-fertilization (hpf); epiboly - 5 hpf; blastopore closure - 8 hpf; and appearance of the optic vesicle - 13 hpf. One hundred embryos were selected from each ontogenetic stage and chilled at - 10°C for 6 or 10 h. The results were analysed using analysis of variance (ANOVA) and Tukey's test at a 5% significance level. A significantly greater number of completely developed live larvae were observed following embryonic treatment with a cryoprotectant solution that contained 17.5% sucrose and 10% methanol. There was no survival for embryos cooled at - 10°C in initial developmental stages (1, 2 and 5 h hpf). Furthermore, higher survival rates were observed when embryos were treated at more advanced developmental stages (8 and 13 hpf). Therefore, P. brachypomus embryos at the blastopore-closure (8 hpf) or appearance-of-optic-vesicle (13 hpf) stages should be used for embryo chilling protocols and chilling should be performed using a 17.5% sucrose with a 10% methanol solution at - 10°C for up to 6 h. The best results were obtained with 13-hpf and 8-hpf embryos and cooling at 6 h of storage.

Natural history and biological aspects of dipsadidae snakes: P. olfersii, P. patagoniensis and P. nattereri História natural e aspectos biológicos de serpentes dipsadidae: P. olfersii, P. patagoniensis e P.

ABSTRACT:The technique of cryopreservation of fish embryos has not efficient results yet, however, the cooling of embryos has been used with satisfactory results. The aim of this study was cooling embryos Colossoma macropomum subjected to a temperature of 2ºC at different times of storage. Embryos were used in the following embryonic stages: blastoderm -1.2 hours post-fertilization (hpf), epibolia -5-hpf; closing blastopore -8-hpf; appearance of the optic vesicle -13 hpf. One hundred embryos, of each stage of ontogeny selected, were treated with glucose 0.5 M solution with 10% methanol, glucose 0.5 M with 10% methyl glycol and glucose 0.5 M in dimethylsulfoxide (DMSO) and cooled at 2°C for 6, 8, 10 and 12 hours. Statistical analysis was performed by ANOVA and Tukey test with 5% significance. We observed a significantly higher difference in complete development of live larvae with the group treated with methanol solution of glucose and a greater survival in the embryos at earlier developmental stages (8-hpf and 13-hpf). It is concluded, therefore, that the embryonic stages of closing blastopore (8-hpf) and appearance of the optic vesicle (13 hpf) can be considered the most recommended for use in cooling protocol of embryos of C. macropomum maintained for 8 hours at 2°C.

Snakes have an important biological role in the ecological chain, as well as in scientific researches performed with the venoms produced by them, since the enzyme-protein fractions these substances possess have been studied as pharmacological tools for the discovery of new therapies. Snakes of the genus Crotalus have gained significant relevance in the scientific field, since the venom produced by these reptiles has been the target of researchers in a few decades, due to the composition and the effects that these substances can produce. In Brazil, a single species represents the genus, which is Crotalus durissus. This review demonstrates that even with the advancement in scientific research on the composition, role and application of the venom produced by the subspecies of Crotalus durissus snake, it is necessary to further study their fractions and their action potential, which also demonstrates the how rich are these active components in different fields of biomedicine.