Normal embryonic-hatching process of saffron cod (Eleginus gracilis)
2018
Chen, A.L. | Yoshida, H. | Sakurai, Y.
Embryonic development and hatching process of saffron cod (Eleginus gracilis) were studied in their artificially fertilized eggs at water temperatures and salinity conditions. Eggs were incubated in plastic containers placed in water tanks with natural running water. Eggs failed to develop at temperature above 6degC and salinity below 8.2 in salinity. at all examined conditions. Deformed development and low hatching rate were observed at 4degC and 13-20 in salinity. These results indicate that the optimum temperature for normal embryonic development and hatching could be below 2degC with 20-25 in salinity. Embryonic development was divided into 7 stages from gastrula to 50% hatching at 2degC. At 2degC, hatched larvae's yolk was completely absorbed in two weeks. Most of the hatched larvae were normally developed and a few individuals opened their mouth just after hatching. It was confirmed that saffron cod had advanced morphogenesis at the time of hatching. Despite of normal development of eggs, their hatching rates were extremely low around 30% with gradually increasing water temperature. Natural water temperature and salinity levels in Lake Akkeshi during winter to spring period showed that environmental conditions were extremely stable until melting ice.
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