MORPHOLOGY AND EMBRYOLOGY OF DUPLICITAS POSTERIOR MICE

The duplicitas posterior syndrome, which involves both duplication and reduction of structures in the posterior region of the mouse, was investigated with reference to the morphology and embryology of its various manifestations. The four principal categories of external anomalies are (a) reduction of a hindleg, (b) reduction of a hindleg and development of an extra leg, (c) duplication of hindlimbs, and (d) kinking of the tail. The skeletal elements of the hindlimb girdle and vertebral column caudal to the thoracic region are involved. Various abnormalities of the urinary tract, male genital tract, and posterior end of the hindgut also occur. It appears from study of embryological stages of 10 to 16 days' gestation that the primary definitive effect is on the caudal end of the neural tube. Bifurcation of and apparent budding off from the primary neural tube of an accessory neural tube with accompanying limb and tail involvement are found. This doubling process may be preceded by prior subdivision of chordamesodermal tissues. The abnormalities of the urogenital and hindgut tissues are probably secondary to the duplication of axial and appendicular elements. Genetic tests indicated that the syndrome has a multifactorial basis, probably involving at least two recessive genes. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company