Spinal Segmental Position Relative to the Vertebrae in Korean Water Deer and Siberian Roe Deer.

The length of the spinal cord differs from that of the vertebral column in vertebrates, and their segmental positional relationship exhibits significant variability and complexity. However, research on the spinal cord structure of the Korean water deer and Siberian roe deer remains unexplored. This study aimed to investigate the anatomical structure of spinal cord segments and their association with vertebrae in these species, as well as to compare the findings with those from previously studied species. Morphometric analyses of the spinal cords and vertebrae were conducted using various measurement parameters. Notably, the cervical enlargement extended from C6 to T1, and the lumbar enlargement from L4 to S1, with significant decreases in spinal segment length observed in these regions. Transitions were noted around these enlargements, including shifts from caudal to cranial in spinal segments relative to vertebral segments and from acute to more obtuse trapezoidal shapes in dorsal rootlets. We propose that reduced growth rates at enlargements determine the positional relationship between the spinal cord and vertebrae. Since this study provides the first anatomical characterization of the spinal cord in these two deer species, our findings advance our understanding of spinal cord structure in Cervidae. Furthermore, through comparative analysis with previous studies, these findings elucidate the segmental positional relationship between the spinal cord and vertebral column, providing a foundation for further morphological and embryological studies across various species.