Thermal resistance traits of the clonal silver crucian carp Carassius langsdorfii and evaluation of these traits using primary culture cells

The thermal resistance traits of three clonal lines of the silver crucian carp Carassius langsdorfii (SCC-1, -2 and -3) were investigated. Individual juvenile fish reared at 20°C were exposed to thermal stress at 36.5 ± 0.5°C and their death times during this exposure were measured. The death times of SCC-2 and SCC-3 fish were 66.6 ± 31.2 and 144.7 ± 49.8 min, respectively. In contrast, all SCC-1 fish survived under these conditions. Furthermore, the thermal sensitivity of primary culture cells from each clone was determined at 37, 40 or 43°C by the Trypan blue assay. Under all treatment conditions, the thermal sensitivity of the SCC-1 primary cultures was lower than those of the others. These results estimated the correlation between the in vivo and in vitro thermal resistances. Therefore, the use of primary culture cells to evaluate thermal resistance could be a useful method of selection breeding.