Hybridisation of Danios and Devarios

I frequently receive correspondence regarding the possibility of hybridisation of both Danios and Devarios. I am not sure why people are interested in this subject unless it is to produce some sort of hybrid which will be attractive to the aquarium trade or maybe just to be able to say that ‘I have been successful in producing a hybrid of Danio X and Danio Y’. If it is for scientific purpose, then I can understand some of the reasons for wanting to produce hybrids.

In order to produce a possible hybrid, one should understand that both species should be closely related. It would be pointless trying to hybridise a Danio and a Devario species by natural methods. The chances of success would be zero. In previous correspondence with Dr Dave Parichy of the University of Washington he revealed that he had been successful in producing hybrids of Danio rerio and several other Danio species using in vitro fertilization techniques. The resulting hybrids always resemble Danio rerio in appearance and are infertile. In the crosses between Danio rerio and Danio nigrofasciatus, the resulting hybrids (F0) were in some cases capable of producing fertile eggs and in others not. The fertility rate was greatly reduced in all cases for F0 eggs / fry. The fertility of the F1 hybrids was again greatly reduced and only a small number of fish produced fertile eggs. The F2 fish were almost completely infertile.

Larissa Patterson also of the University of Washington was successful in crossing the spotted morph of Danio kyathit with the striped morph. Males of one were crossed with females of the other morph and vice versa. The resulting fish were in general not as attractive as the spotted kyathit. The hybrids were at least partially fertile although there appeared to be decreased viability. It should be stressed that this work was done for purely scientific purposes.

Whether other attempts to produce hybrids of Danio species have been made does not seem to have been reported in the scientific press.

My own feeling is that nature produced a perfect specimen of a species. Why should we think we can improve on it?