MORPHOLOGICAL AND MORPHOMETRIC FEATURES OF THE DEFORMED CERVICAL AND CAUDAL VERTEBRAE IN A NEW MUTANT KNOTTY-TAIL (KNT KNT) MOUSE/

Morphological and morphometric examinations were conducted on skeleton s of knotty-tail (knt/knt) mouse, a new autosomal recessive mutant. Th e knt/knt mice have short and knotty tails. The number of caudal verte brae is reduced and their deformed caudal vertebrae show no parallelis m between the epiphyseal planes and no osseous fusions. Morphological changes, except for the caudal vertebrae, are confined to the neural a rches of the axis in knt/knt mice. As for the tail anomaly the knt gen e seems to have the same action as the tk gene, but knt/knt mice diffe r from other strains with respect to cervical morphology. The morphome try of the caudal vertebrae revealed that knt/knt mice have a disconti nuous and lower ratio of width to length after their 6th caudal verteb ra. The morphometry also revealed that knt/knt mice have 1) broadened cervical vertebrae in the transverse direction, 2) thickened ventral l amina of the 6th cervical vertebra and 3) shortened and broadened vent ral tuberculum of the atlas. From these results, the knt/knt mouse was considered to be a new pleomorphic mutant.