Hybridization Experiments in Cyprinid Fishes. VIII. Two Kinds of Reciprocal Crosses, Pseudogobio esocinus×Pseudorasbora parva and Biwia zezera×Pseudorasbora parva

抄録

The artificial crosses of Pseudogobio esocinus _??_ ×Pseudorasbora parva _??_ and Pseudorasbora parva _??_ ×Biwia zezera _??_ were successful and three hybrids were reared until they reach one or two-year old. All of them turned out to be neuters. They are not only intermediate in morphological characters but also have typically intermediate behavior between their parental forms. Time of hatching is also nearly intermediate.
In the cross of Pseudorasbora parva_??_×Pseudogobio esocinus _??_, however, only about four per cent of eggs developed to gastrula and all of them never went beyond the closure of the blastopore.
In the cross of Biwia zezera _??_ ×Pseudorasbora parva _??_, the fertilization were successful, while hybrids could not survive beyond 12 days after hatching.