85 SYNERGISTIC EFFECT OF DEHYDRATION AND LOW TEMPERATURE ON THE SURVIVAL OF PANGASIUS CATFISH (PANGASIANODON HYPOPHTHALMUS) EMBRYOS

Abstract

Embryo cryopreservation is an important need for industrial catfish production, as well as for biodiversity conservation. However, due to the limit of membrane permeability and dehydration in fish embryos, no successful cryopreservation method has been reported. We present herein results of the effect of dehydration and low temperature on the survival of catfish embryos, to understand their cryobiological behaviour and develop an efficient freeze method for this species. Embryos at blastocyst stage were collected at 10 h after insemination and kept in a water tank with an air pump. Embryos with somites and optic cups clearly distinguished were selected and treated according to 4 treatment groups: group 1, control group: embryos were kept in water at room temperature for 2 h; group 2, treated for dehydration: embryos were kept in 1 M or 2 M sucrose solution for 2 h at room temperature; group 3, treated for low temperature: embryos were kept in water for 2 h at 0°C; and group 4, treated for dehydration and low temperature: embryos were kept in 1 M or 2 M sucrose solution for 2 h at 0°C. After treatments, all embryos were washed twice in water and incubated in separated water tanks for 2 days. The survival of embryo was evaluated by the rate of intact and hatched embryos during the first day after treatment. Statistical analysis was performed using one-way ANOVA followed by Dunnett’s test. Our results showed that in the control group, all of the embryos were intact and hatched. In the group 2, the survival rate of embryos treated with 1 M sucrose was not different compared with the control group. However, in this group, no hatched embryos were obtained when treated with 2 M sucrose (Table 1). Also, no hatched embryos were observed when they were kept at 0°C without dehydration (group 3). A significant improving hatching rate was obtained in group 4 for embryos treated at 0°C and dehydrated in 2 M sucrose (90 v. 0% in group 3; P < 0.05). In conclusion, the combined treatment of dehydration (in 2 M sucrose concentration) and low temperature (at 0°C) can result in synergistic effect that are able to protect embryos from damages caused by treatment with either low temperature or dehydration conditions. Table 1.Treated catfish embryos This work was supported by a project from MARDVN.