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

Abstract

Novel bio-imaging techniques such as micro-Computed Tomography provide an opportunity to investigate animal anatomy and morphology by overcoming limitations imposed by traditional anatomical drawings. The primate genital bones are complex anatomical structures whose occurrence in both male penis (baculum) and female clitoris (baubellum) may be difficult to assess in individual cadavers. We tested a 3-step methodological protocol, including different techniques ranging from inexpensive/simple to more expensive/sophisticated ones, by applying it to a sample of primate species, and resulting in different levels of data complexity: (1) presence/absence manual palpation method; (2) 2D X-ray plates; 3) 3D micro-CT scans. Manual palpation failed on 2 out of 23 specimens by detecting 1 false negative and 1 false positive; radiography failed once confirming the false positive, however firmly disproved by micro-CT; micro-CT analysis reported the presence of 9 bacula out of 11 male specimens and 1 baubellum out of 12 female specimens. A different baculum position was identified between strepsirrhine and haplorrhine species. We also aim to assess micro-CT as a non-invasive technique providing updated anatomical descriptions of primate ossa genitalia. 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 identified: 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 high resolution of micro-CT 3D-images of primate genital bones disclosed additional form variability to that available from genital bone 2D images of previous studies, and showed for the first time new internal and external morphological characters. Moreover, micro-CT non-invasive approach proved appropriate to recover much of scientific knowledge still hidden and often neglected in both museum specimens and primate cadavers only destined to necropsy.Novel radiological techniques have greatly advanced our knowledge in animal morphology, allowing to quantify internal anatomy with higher degree of accuracy, also using non-invasive approaches. In the past, anatomical studies were based on bi-dimensional drawings and/or photographs that allow to obtain limited information about size and shape. To date, bio-imaging techniques overcome these methodological limits since they produce virtual 3D models which, in addition, provide the access to more detailed descriptors of morphological variation. The availability of micro-CT imaging has increased over the last decade and has shown its utility in many biological [1-3] and medical applications [4][5][6]. In comparison with other imaging techniques, the strengths of micro-CT lie in its high-resolution imaging, s...

The ultimate database to (re)set the evolutionary history of primate genital bones

“…In our study, all museum and fresh samples have undergone the same analytical investigation 91 with no exceptions. We acknowledge that although micro-CT scan is a well-known reliable technique to detect bones inside soft tissues (i.e., bones usually totally radiopaque to X-rays), the actual presence of genital bones have traditionally derived (but see 92 ) from direct pieces of evidence (i.e., invasive dissection and/or histochemistry).…”

“…Samples were of two kinds: (1) fresh samples (N = 16; 9 clitorises and 7 penises) and (2) museum wet samples (N = 132; 1 baculum , 23 clitorises, 92 penises, 8 female whole bodies, 8 male whole bodies). Fresh samples were obtained from fresh cadavers of primate specimens, dead for natural causes, before necropsy investigations (in collaboration with Italian Istituti Zooprofilattici Sperimentali, see 91 for further details). Museum wet samples were obtained from (i) the «Museo di Zoologia dell’Università di Torino» (MZUTT, Turin, IT, theriological collection 101 ; N = 1); (ii) the Natural History Museum «La Specola», (NHMLS, Zoological Section, Florence, IT, non-human primate collection 102 ; N = 1); (iii) the American Museum of Natural History (AMNH, New York, USA, Vertebrate Collection Database available at http://sci-web-001.amnh.org/db/emuwebamnh/index.php ; N = 46); (iv) the National Museum of Natural History (NMNH, Washington, D.C., USA, Mammal Collection Database available at https://collections.nmnh.si.edu/search/mammals/ ; N = 84).…”

“…In order to obtain data about the genital bone either presence or absence, the 3-step methodological protocol proposed by Spani et al 91 was applied (i.e., palpation method, X-rays, and micro-CT scanner). Three different micro-CT scanners have been used depending on the location of collected samples, whether Italy (same used by Spani et al 91 ) or USA. (PHOENIX V|TOME|X S, available at AMNH, and PHOENIX V|TOME|X M, available at NMNH) and machine settings have been reported in Table 2 .…”

“…The last kind of doubtful cases of genital bone occurrence emerged from micro-CT scanned samples (for methodological details please see 91 ). We classified these cases as ‘doubtful’ (noted with ‘?’ in Supplementary Table S2 , columns ‘Present study data—micro-CT’) because reconstructed slices showed a ‘shadow’ (where the baculum is usually placed) characterized by grey levels which were intermediate between those typical of a bone absence and those typical of a presence.…”

Chemical analysis and computed tomography of metallic inclusions in Roman glass to unveil ancient coloring methods

“…A customizable choice of scanning parameters enables to enhance the image quality depending on the sample characteristics (especially size and density). Small specimens can be scanned with high accuracy, while for bigger samples the field of view can be extended by means of mechanical translation of the detector (tile scanning techniques) 34 , 35 . The system comprises a micro-focus X-ray tube (Kevex mod.…”