Effect of different permeable and non-permeable cryoprotectants on the hatching rate of rainbow trout (Oncorhynchus mykiss) embryos

The purpose of the present study was to investigate the toxicity of cryoprotectants on the hatching rate of rainbow trout (Oncorhynchus mykiss) embryos. Epiboly and first eye pigmentation stage embryos were immersed in six permeable cryoprotectants, dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), propylene glycol (PG), ethylene glycol (EG), and acetamide (Ac), in concentrations of 1–5 M for 5 or 10 min and two non-permeable cryoprotectants, sucrose (Suc) (10%, 15%, 20%) and polyvinyl pyrrolidone (PVP) (5%, 10%, 15%) for 5 min. The embryos were then washed and incubated until hatching occurred. The toxicity of the cryoprotectant was assessed by the hatching rate. The results illustrated that permeable cryoprotectant toxicity for rainbow trout embryos increased in the order of PG < DMSO < MeOH < Gly < EG < Ac. The hatching rate of the embryos treated with permeable cryoprotectants decreased (P < 0.05) with increased concentration and duration of exposure. There were no significant decreases in hatching rate of embryos treated with sucrose and PVP with the increase of concentration; sucrose had higher hatching rates than PVP. Rainbow trout embryos at first eye pigmentation stage exhibited greater tolerance to cryoprotectants than embryos at epiboly stage.