Female medaka, Oryzias latipes, is known to deposit their eggs on substrates in shallow waters. However, there is a possibility that the eggs will be exposed to the air and dry when the surrounding water level falls. In the present study, we examined the resistance to desiccation of fertilized eggs of medaka. Each egg was placed in a plastic dish filled with water and subjected to one of the following three treatments for one or three days at different times after fertilization: 1) placed on a wet filter paper and exposed to the air (wet group), 2) placed on a dry dish (dry group), and 3) kept in water (control). Most eggs in the control and the wet group hatched, and all the eggs of the dry group died. The results of the wet group indicate that fertilized eggs of medaka have some resistance to desiccation.
