Removal of the Membrane of the Dog Salmon Egg by Means of Proteolytic Enzymes∗

Abstract

Introduction In connection with the problems of the hatching enzyme, properties of membrane of fish egg have become a subject of discussion not only in chemical aspect but likewise in biological point of view. Surveying the hatching enzyme of teleostean fishes, Bourdine (′26) has suggested that the egg membrane of the Atlantic salmon, Salmo salar, is attacked to some extent by pancreatin; on the same material Young and IMMAN (′38) have reported that it is not attacked by trypsin (pH 8.4) but is slightly by pepsin (pH 2.6). From the examination of effects of various enzymes on the membrane of Oryzias-egg, Ishida (′44) has also stated that pancreatin and trypsin digest the egg membrane completely. More recently, the junior author has shown that the envelopes of lamprey egg are composed predominantly of protein and also that with use of pepsin dissolved in M/200 Ringer's solution (pH 1.8) the naked fertilizable egg is obtained (Yamamoto ‘56). The present investigation makes a part of a series of studies in the activation or fertilization of fish eggs, and some different kinds of proteolytic enzymes were employed in order to find a procedure for removing the membrane of the egg of dog salmon, Oncorhyn-chus keta∗∗. It is a pleasure to acknowledge our gratitude to Prof. A. Ichikawa for his encouragement. We are also indebted to the members of the staff of the Hokkaido Fish Hatchery for their allowing the collection of the material used in the present study. © 1957, The Japanese Society of Fisheries Science. All rights reserved.