抄録
Morphological changes of unfertilized and fertilized eggs of the Japanese sardine Sardinops melanostictus were observed continuously. Unfertilized sardine eggs could be divided into three types on the basis of their morphology: a distorted type, a narrow perivitelline-spacetype, and a normal perivitelline-space type. The first type of eggs disintegrated and sank to the bottom of the containers in a short time. The latter two types of eggs formed not only a perivitelline space but also a blastodisc. They disintegrated gradually within 12 hours after stripping. Common to eggs of these three types, the egg membrane finally broke and the egg's contents were mainly lost. The examination of the field-collected eggs showed that some wild eggs were very similar in their morphological characteristics to unfertilized and disintegrated sardine eggs mentioned above. These facts suggest that unfertilized sardine eggs may be commonly present in natural spawning.
