Studies on the interfamiliar crossing between loach Misgurnus anguillicaudatus) and goldfish (Carassius auratus)

Abstract

This research was made to examine the reciprocal cross between mud loach (Misgurnus angaillicaudatus (C.)) and goldfish (Carassius auratus (L.)) which is of a different family, and to explain the development and the effect of the genes.
At the early stage of development, it was found that more dead eggs were among the interfamiliar hybrid ones than in the case of the normal cross, and the number of them were much more increased at the gastrula stage.
The larvae which were produced from M. a. (=mud loach) _??_×C. a. (=goldfish) _??_ survived for 14 days and those produced from C. a. _??_×M. a. _??_ survived for 24 days, but many of these larvae had an obstacle of development in the head, the tail and the yolk sac.
The time needed for hatching C. a. of the normal development was twice as long as that for hatching M. a. of the normal development, when both of them had been kept under the same condition of temperature (19-21°C) by the thermostat. But C. a. _??_×M, a. _??_ hatched faster than C. a. of the normal development, and M. a. _??_×C. a. _??_ hatched slower than M. a. of the normal development.
The nuclei of the normal larvae of M. a. were found to be very small compared with that of C. a. In the case of M. a. _??_×C. a. _??_, however, the nuclei were bigger than those of the normal larvae of M. a., while the nuclei of the larvae hatched out of C. a. _??_×M. a. _??_ were smaller than those of the normal larvae of C. a.
The number of the myotomes of normal larvae of M. a. were greater than those of the normal larvae of C. a. But through the experiment of M. a. _??_×C. a. _??_, it was known that the number of the myotomes were less than those in the case of the norrnal larvae of M. a. C. a. _??_×M. a. _??_ showed that the ndmber of the myotomes was bigger than in the case of the normal larvae of C. a.
The normal larvae of M. a. had no melanophores immediately after having been hatched, but the normal larvae of C. a. had already melanophores ranging from 120 to 240 as soon as they were hatched. More melanophores, however, appeared in the case of M. a. _??_×C. a. _??_ than in the normal larvae of M. a., and in the case of C. a. _??_×M. a. _??_ they appeared less in numder as compared with the normal larvae of C. a.
From the facts mentioned above, I think I can conclude that the size of nucleus of larvae, developmental rate of the egg, the number of myotomes, and that of melano-phores are effected by the paternal as well as maternal genes. Therefore, I can not approve of the parthenogenesis which LOEB had publicized, and I am convinced from the facts of my experiments that the interfamiliar hybrids can be produced by the fusion of the egg nucleus and the sperm nucleus concerned at the moment of the insemination.