Abstract
In this article, we tried a newly developed condition for long-term preservation of fertilized silkworm eggs. The “Modified 2-years preservation method of silkworm eggs” was applied to some varieties of commercial silkworm strains. The condition is based on the “2-years preservation” reported by Shimizu et al. (1994), in which we altered the 6th intermediate care at 15°C for 1 day into 10°C for 10 days. Hybrid eggs preserved by this method showed practical hatchability as high as 65% without causing any defects on larval growth. In the case of original strains, however, hatchabilities were relatively low and a serious inbalance was often observed in the sexual ratio of the hatched larvae even if the “Modified 2-years preservation of the eggs” was applied. However, it was possible to maintain the eggs in next generation for another 2 years, showing certain improvement of hatchabilities in many strains. Good larval growth was obtained less than 1 year after the preservation even if they were suppressed by 2 years preservation. Thus, we consider that the “Modified 2-years preservation” is useful in maintaining original silkworm strains efficiently. In order to improve the hatchability of long-term preserved eggs, it was effective to keep a sufficient air supply by inserting spacers between each egg card.
