Spontaneous pre-axial polydactyly in Swiss mice

ABSTRACT: Spontaneous polydactyly has been described in several species, but only one report about it in Swiss mice. The aim of the current study was to report the spontaneous occurrence of pre-axial polydactyly in Swiss mice. Clinical examination showed one extra toe laterally to the first digit, in the plantar region, alopecia in the back, altered face growth anatomy and changed perineal region anatomy. Pre-axial polydactyly in the tibial side, fused metatarsals and Y-shaped free phalanges were evidenced in the radiographic images. Pre-axial polydactyly observed in the plantar region differed from that in reports on albino Swiss mice with post-axial polydactyly (Po/Po+) phenotype featured by one extra toe in the ulnar side of one, or both, front limbs, which is the dominant feature. The observed findings highlight the importance of both clinical examinations and close attention by professionals involved in rodents’ breeding on physical changes resulting from different causes, including the genetic ones, since they reveal mutations and, sometimes, new biomodels.