External and Internal Abnormalities Exhibited by the Crossbreds between the Ear-Tuft(hfd)and Throat-Tuft(hfdTt)Mutants of Japanese Quail(Coturnix coturnix japonica).

Abstract

Some of crossbreds between ear-tuft (ET, hfd/hfd) and throat-tuft (TT, hfdTt/hfdTt) mutant quail showed assorted anomalies involving tufts, ear-opening abnormalities, extra bones projecting from the throat, and head-skeleton abnormalities as their parental quail. They were mostly classifiable as ET-or TT-type abnormality, indicating possible correspondence between phenotypes and genotypes. Incidences of 15-day embryos with external abnormalities ranged between 27%-51%, being significantly lower than those of 5-day embryos with hyomandibular furrow (HF) defects (58%-64%). The differences in incidences of abnormal embryos at the two developmental stages suggested the existence of repair mechanisms for the HF defect. Incidences of 15-day embryos having head-skeleton abnormalities ranged between 59%-77%, being significantly higher than those of tufts, ear-opening abnormalities and/or extra bones. These results show that collective investigations on many kinds of characters may be necessary to find out a key character showing accurate correspondence to a genotype when gene effect is expressed in different organs and tissues. Incidences of the head-skeleton abnormalities in the crossbreds mentioned above (59-77%) were significantly lower than those observed in both intra-ET-(87%) and intra-TT-strain crosses (88%), which suggested that interaction among hfd and hfdTt genes and background genes lowers the incidence of the head-skeleton abnormalities. The head-skeleton abnormality was found to be an inadequate character for an allelism test.