Pedicle and first antler formation in deer: Anatomical, histological, and developmental aspects | Rosenstock- und Primärgeweih- Bildung bei Hirschen: anatomische, histologische und entwicklungsbiologische Aspekte Formation du pivot et du premier bois chez les Cervidés: aspects anatomiques, histologiques et de biologie du développement

Formation of primary cranial appendages (pedicles and first antlers) in deer is initiated by a specialized periosteum, for whichGOSS (1983) introduced the term antlerogenic periosteum. The antlerogenic periosteum (AP) is located on the external frontal crests, this area of the deer skull most likely being of neural crest origin. As was discovered byHARTWIG (1968b) andHARTWIG andSCHRUDDE (1974), AP is capable of autonomous differentiation even when grafted to other regions of the body, thereby causing the growth of ectopic pedicles and antlers. This means that the cells of the AP are determined for pedicle and antler formation. There is further evidence that the cells forming the bony component of regenerating antlers are derivatives of the AP and that the AP contains crucial morphogenetic information for antler shape. The cells of the AP and its derivative, the antler perichondrium, exhibit features (high glycogen content, long life spanin vitro) that are normally only found in embryonic cells. These findings support our hypothesis, originally based on studies of double-head antlers, that the growth of both primary cranial appendages (pedicles and first antlers) and of regenerated antlers depends on a population of antlerogenic periosteal stem cells.In fallow and red deer, formation of both pedicles and antlers occurs by a process of modified endochondral ossification, whereas in the roe deer there is evidence that the pedicles are formed solely by intramembranous ossification, while antler growth proceeds by endochondral ossification. The transformation of pedicle skin to antler velvet is a specific reaction of the integument to an inductive signal originating from subdermal (presumably periosteal/perichondrial) antlerogenic cells. Occurrence of ectopic antlers reveals that also skull bone periosteum from outside the pedicle anlage area is capable of producing antler structures when exposed to strong unphysiologic stimuli. Contrary to AP, this periosteum is however not determined for cranial appendage formation, since its transplantation to other body regions does not cause ectopic pedicle and antler growth.