Experimental Investigations of Morphogenesis in the Growing Antler

Abstract

ABSTRACT Investigations of the morphogenesis of antler growth have been undertaken in the sika deer (Cervus nippon). Operations were performed on the left antlers, while the intact right antlers served as controls. Amputation of the terminal centimetre of growing antlers seriously impedes further development except for the production of an abortive outgrowth from the stump. By contrast, transverse amputation through the middle of the pedicle is followed by normal antler formation. Removal of the entire pedicle permits antler development to occur, although at a retarded rate. Therefore, antlerforming potentiality resides in the growing tips of the elongating antler as well as in the tissues of the entire pedicle. The extent of morphogenetic regulation for defects surgically inflicted on the antler bud or pedicle depends on the age of the antler and the location of the injury. Excision of the posterior halves of 1-inch antler buds results in corresponding deficiencies in the antlers produced. The same injury to an extremely rudimentary bud, however, is followed by considerable regulation, and removal of the posterior half of the pedicle prior to shedding of the old antler has no effect on the normal development of the resulting antler. Ablation of anterior or median halves of pedicles likewise causes no morphogenetic abnormality, but if the lateral half of the pedicle is removed no antler develops. The importance of the lateral half of the antler-forming structure is further illustrated by the fact that a complete and normal antler can grow from just the lateral half of a pedicle or of a 1-inch antler bud. The morphogenetic field of the antler can give rise to double antlers if bisected longitudinally; transverse subdivision, however, does not alter subsequent normal production of a single antler. It is proposed that a relationship between the initial mass of antler-forming material and the degree of morphogenetic expression may possibly exist.