Hatching Enzymes in the Japanese Eel

Before the hatching of teleost embryos, the egg envelope (chorion) is digested by hatching enzymes, which are proteolytic enzymes secreted from hatching gland cells of the embryo. The functional property and molecular structure of the hatching enzyme and its gene structure have been mainly elucidated in a freshwater teleost, medaka (Oryzias latipes) (Yasumasu et al. 1994). Recently, the developmental expression of hatching enzyme genes has been well studied in medaka and some other freshwater fishes, masu salmon (Oncorhynchus masou) and zebrafish (Danio rerio) (Inohaya et al. 1997). However, for marine teleosts such as the Japaneseeel, Anguilla japonica, which hatch in seawater, no information is available on hatching enzymes.