Preleminary Studies on Cryopreservation of Common Tench, Tinca tinca, Embryos

Abstract

Vitrification could provide a promising tool for the cryopreservation of fish embryos. However, in order to achieve cryopreservation using vitrification, chilling sensitivity and cryoprotectants toxicity were determined using tench embryos at four developmental stages (11, 17, 23 and 29-h). Embryos treated with alcalase (2mL 998ml 2mm at 22°C) were exposed to chilling with/without warming. Other embryos were exposed to methanol and glycerol at the concentration of 10% and 20% for periods of 20 min. Thereafter, embryos were incubated at special incubator to determin the hatching rates. Regarding chilling sensitivity, the hatching rates of embryos decreased significantly (P <0.001) after exposure to 0°C at all developmental stage except 29-h stage. The same results were reported after exposure to chilling followed by warming. It was found that the 11-h embryonic stage was most sensitive to chilling preservation. Whereas, the 29-h stage exhibited the least sensitivity, while 17-h and 23-h stages were intermediate in their sensitivity to chilling. The toxicity of methanol increased significantly (P <0.001) with developmental stage for 11-h, 17-h and 23-h stages. The largest change was a reduction in the toxicity of methanol in 29-h embryos. The highest hatching rates of tench embryos were obtained with 29-h embryos using various concentrations of methanol. The survival trends of different stages of tench embryos exposed to glycerol concentrations were approximately similar to those embryos exposed to methanol concentrations except for 11-h embryos which showed no hatching with both glycerol concentrations. Concerning the viability of embryos after vitrification, unfortunately, it could not obtained any viable embryos in any of conditions examined. In conclusion, as it was quite difficult to vitrify the tench embryos during this study using various vitrifying solutions and the method reported by Chen and Tian (2005) and so further studies using other developmental stages, basic, washing and vitrifying solutions are needed to achieve successful cryopreservation.