Dechorionation of fertilized eggs and embryonic development in arctic rainbow smelt Osmerus eperlanus mordax

In order to establish the basement for developmental engineering in osmerid fishes, a dechorionation technique and developmental stages were described using rainbow smelt Osmerus eperlanus mordax. Eggs of rainbow smelt were fertilized with tap water. One minute after fertilization, dechorionation was performed by treatment with smelt’s Ringer solution: SRS (128 mM NaCl, 2.8 mM KCl, 2.7 mM CaCl2) containing 0.1 % trypsin and adjusted to pH 11.0 with 1 N NaOH. The chorion was digested completely within 5 h at 10 °C and the resulting denuded embryos developed normally under artificial culture conditions with SRS containing 1.6 % albumen before embryonic body formation, and then tap water. At the hatching stage, the average survival rate was 37.8 %. Embryos without the chorion were highly transparent and organogenesis was easily observed under a stereomicroscope. Embryos developed slowly to the embryonic body formation stage (66 hours postfertilization (hpf)) and hatching stage (22 day postfertilization (dpf)) at 10 °C. The embryonic development of rainbow smelt was similar to that of zebrafish Danio rerio and generally followed the basic developmental pattern of teleosts. These characteristics suggest that developmental engineering technology developed in model fishes can be applied to rainbow smelt.