A 3D journey on virtual surfaces and inner structure of ossa genitalia in Primates by means of a non-invasive imaging tool

A 3D JOURNEY ON VIRTUAL SURFACES AND INNER STRUCTURE OF OSSA GENITALIA IN PRIMATES BY MEANS OF A NON-INVASIVE IMAGING TOOL Federica Spani1*, Maria Pia Morigi2,3,4, Matteo Bettuzzi2,3,4, Massimiliano Scalici1, Monica Carosi Department of Sciences, Roma Tre University, Rome, Italy Department of Physics and Astronomy, University of Bologna, Bologna, Italy Historical Museum of Physics and "Enrico Fermi" Study and Research Center, Rome, Italy National Institute of Nuclear Physics, Rome, Italy Bio-imaging techniques, such as micro-Computed Tomography, allow to study known anatomical structures in a new perspective, overcoming obvious limits of drawings available in old anatomical/morpho-functional texts. This is the case of primate genital bones placed inside male penis (baculum) and female clitoris (baubellum). This study aims at proving micro-CT as a non-invasive technique to obtain 3D high resolution virtual reconstructions of ossa genitalia, unveiling new anatomical features. We test a 3-step methodological protocol including both inexpensive simple techniques to more expensive sophisticated ones, reaching different levels of data complexity: (1) presence/absence manual palpation method; (2) 2D X-ray plates; 3) 3D micro-CT. Manual palpation failed on 2 out of 23 specimens detecting 1 false negative and 1 false positive; radiography failed once confirming the false positive, firmly rejected by micro-CT; micro-CT analysis confirmed the presence of 9 bacula out of 11 male specimens and 1 baubellum out of 12 female specimens. A different baculum position was highlighted between strepsirrhine and haplorrhine species. Micro-CT 3D volumes showed the surface of some bones as rough, with a jagged appearance, whereas in others the surface appeared very smooth and coherent. In addition, four main types of bone internal structure were found: 1) totally hollow; 2) hollow epiphyses and solid diaphysis with few or several channels inside; 3) totally solid with intricate Haversian channels; 4) totally solid with some channels (structure of single baubellum scanned). Ossa genitalia appeared as a living tissue having its own Haversian-like channels. The morpho-functional evolution of ossa genitalia in Primates is a still unresolved biological question, that needs to be explored in-depth. The high resolution of micro-CT 3D-images of primate genital bones disclosed additional form variability to that available from genital bone drawings of old studies and showed for the first time new characters about external and internal morphology of 9 bacula and one baubellum. With an increased sample size, new genital bone features now disclosed will allow to investigate new functional hypotheses. Moreover, micro-CT non-invasive approach proved appropriate to recover much of scientific knowledge still hidden and often neglected3 in both museum specimens and autopsy primate cadavers.