Recently, I crossed my Rainbow guppies with Santa Maria Endlers to increase their fitness. It is too early in this project to report on any fitness improvements. However, I can say that I am delighted with the initial phenotype results. The first generation (50% Rainbow and 50% Endler) produced a mixture of phenotypes but no significant problems; the second generation (75% Rainbow and 25% Endler) produced plenty of gorgeous, Rainbow-type individuals (Figure). Attached article explains the importance of choosing which sex to use for the outcross, “sperm turnover” time, etc. It also discusses inbreeding’s effect on fitness–a sorely neglected subject in the aquarium hobby.
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