Chilling curves for Piaractus mesopotamicus (Holmberg, 1887) embryos stored at −8°C

Abstract

The present study investigates the effect of different slow chilling curves on the storage of pacu (Piaractus mesopotamicus) embryos submitted to chilling at -8°C. Embryos at the blastopore closure stage were divided into two groups: G1 - embryos exposed to cryoprotectant solution containing methanol (10%) and sucrose (0.5 M), treated as follows: (T1) taken directly from room temperature to the refrigerator without being submitted to the curve; (T2) chilling curve of 0.5°C/min; and (T3) chilling curve of 1°C/min; and G2 - the cryoprotectant solution alone was submitted to these same temperatures, receiving the embryos only after temperature had decreased, corresponding to treatments T4, T5 and T6, respectively. Treatments were kept at -8°C for a period of 6 h. Embryo development was evaluated for each treatment, with six replicates in an entirely randomized design. Survival among embryos not submitted to refrigeration was 94.3 ± 8.05%. Percentage of total larvae (TL) and addled eggs (AE) did not differ statistically between the groups, although percentage of swimming larvae (SL) exhibited higher values in G1 for the 1°C/min curve. Furthermore, when comparing the three chilling curves, a decrease of 1°C/min resulted in the highest TL percentage (90.85%), followed by the 0.5°C/min curve (78.52%). Thus, the use of 1°C/min chilling curves is recommended for P. mesopotamicus embryos stored for 6 h at -8°C.

Chilling of Steindachneridion parahybae (siluriformes: pimelodidae) embryos

“…When cells are submitted to low temperatures, there is a reduction in cellular and enzyme activities [16,27]. Thus, it was expected that after returning to room temperature, cellular activities would be restored and the embryonic period would be delayed for a certain time corresponding to the chilling period, similar to what has been observed in studies with other species [18,19]. However, the S parahybae embryos at the embryonic stage that usually presented the best results behaved differently.…”

“…3). Embryos at the free-tail embryonic stage (19 hpf, mean water temperature: 26.25 AE 0.40 C) were counted (100 per replication) and placed in Falcon tubes (50 mL), where they received 10 mL of cryoprotectant solution: M10 þ S (10% methanol [Merck] and 0.5-M sucrose), and then subjected to a chilling curve as described by Lopes et al [19]. They were then taken to the refrigerator, kept for 6 and 12 hours at subzero temperatures (À6.44 AE 1.39 C), and then transferred to conical hatcheries (1.5 L), remaining there until the moment of hatching.…”

“…Unlike the technique of cryopreservation, where the embryos are stored in nitrogen for a long time, the chilling technique consists of submitting the embryos to temperatures near zero (between À10 C and 0 C), normally in a refrigerator, for a short period of storage [11,13,16]. The use of this technique has shown positive results for Piaractus mesopotamicus embryos stored at subzero temperatures for 6 hours, without a significant reduction in hatching rates, which were 69.2% [17], 55.2% [18], and 90.2% [19], according to the stage of embryonic development, cryoprotectant solution, and curve used for cooling. However, data on percentages of normal larvae were not presented.…”

Surubim-do-Paraíba oocytes viability after being exposed to different cryoprotectants

“…It is also important to test new cryoprotectants with the same characteristics. Methanol has properties that are common among short-chain alcohols, such as the ability to lower the phase transition temperature of the lipid membrane; and this mechanism of protection reported positive results for the cryopreservation of fish embryos (LOPES et al, 2012(LOPES et al, , 2015. Solutions of PG promoted small and amorphous ice formation due to their high viscosity at temperatures below zero.…”

Effects of cryoprotectants and low temperatures on hatching and abnormal embryo development of Prochilodus lineatus (Characiformes: Prochilodontidae)

“…Despite the high sensitivity to cold reported in the literature for temperate climate fish species, such as Sciaenops ocellatus and Tinca tinca (Gwo et al, 1995;ElBattawy, Linhart, 2009), and neotropical species, such as Piaractus mesopotamicus Lopes et al, 2013), cooling protocols use temperatures below or close to 0ºC in their attempt to prolong embryonic development by long periods (Ninhaus-Silveira et al, 2006;Fornari et al, 2012). Thus, in this study, it was found that the use of a higher temperature (5ºC) allowed an increase in tropical fish embryonic survival and prolonged embryonic development time sufficiently to achieve a 12-h cooling technique, although morphological damage could not be controlled.…”