Inheritance of Shoulder Spotting in the Red-base Tetra (Characidae: Hemigrammus stictus)

The Red-base tetra (Hemigrammus stictus) exhibits two phenotypes associated with shoulder spotting. Fish either possess a prominent black shoulder spot located directly behind the operculum or lack this spotting pattern. Segregation patterns observed from the progenies of eleven different crosses suggest that the inheritance of shoulder spotting is controlled by the action of two autosomal loci acting in a complementary recessive fashion, with dominance at either locus resulting in the expression of the spotted phenotype.