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

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

Claw asymmetry in crabs: approaching an old issue from a new point of view

Abstract Crabs are considered exceptional examples of antisymmetry resulting from the phenomenon of heterochely. Here we investigate morphometrically both the size and the shape of heterochely in 28 crab species, distributed unequally along a brachyuran phylogeny. We address the importance of investigating claw size and shape for interspecific comparisons by linking geometric morphometric outputs to phylogenetic data for 134 brachyuran species. New indices introduced as new sexual dimorphic characters of size and shape, namely heterometry (right chela size/left chela size) and heteromorphy (Procrustes distance between right and left chelae shape), revealed sexually dimorphic differences in diverse crab species. We demonstrate that both size and shape heterochely occur amongst the examined species, but there are no ecological correlations. Our study demonstrates that claw similarity between two or more species was due mainly to phylogenetic relatedness rather than ecological convergence, suggesting that claw morphological features could be useful morphological markers in phylogenetic studies. Although further investigation is needed, this study represents one of the first to thoroughly analyse the origin and evolution of heterochely within the Brachyura clade

Over and beyond the Primate baubellum Surface: A “Jewel Bone” Shielded in Museums

Computed Tomography (CT), mostly used in the medical field, has also recently been involved in Cultural Heritage studies, thanks to its efficiency and total non-invasiveness. Due to the large variety of sizes and compositions typical of Cultural Heritage objects, different X-ray sources, detectors, and setups are necessary to meet the different needs of various case studies. Here, we focus on the use of micro-CT to explore the morphology and shape of a small, neglected bone found inside the clitoris of non-human primates (the baubellum), which we obtained by accessing two prestigious primatological collections of the American Museum of Natural History (New York, NY, USA) and the National Museum of Natural History (Washington, DC, USA). Overcoming methodological limits imposed by the absence of homologous landmarks, we combined the use of the non-invasive 3D micro-CT and a recently released landmark-free shape analysis (the alpha-shape technique) to objectively describe and quantify the shape complexity of scanned primate baubella. Micro-CT provided high-resolution results, overcoming constraints linked to museum policy about non-disruptive sampling and preserving samples for future research. Finally, it proved appropriate as post-mortem sampling had no impact on protected wild primate populations

"The orchids of the animal kingdom": tackling functional anatomy and phenotypic plasticity of ant nest beetles (Carabidae: Paussus) using 3D models generated by Micro-Computed Tomography (µ-CT)

The genus Paussus is a highly specialized, charismatic group of ground beetles (Carabidae) classified in the subfamily Paussinae. All species of Paussus are obligate myrmecophiles (associates of ants). As with many other myrmecophilous or termitophilous beetles, Paussus have undergone extreme phenotypic adaptations for life with ants, at the level of head, antennae, and prothorax. Host data suggest that Paussus species are likely to be species-specific ant parasites, and the structural modifications of antennae and other body parts are likely under selection by their host ants. Investigating anatomical structures have been fundamental to better understand living organisms, and their interplay with the surrounding environment, which could induce significant morphological variation. In the last few years, bio-imaging techniques paired with geometric morphometrics (GM) overcame the limits of traditional anatomical studies, becoming widely non-invasive and highly informative for both internal and external characters. The use of Computed Tomography (CT) scanners definitively allowed to advance in the knowledge of either known or neglected biological structures. For this project, we used X-ray micro-computed tomography, in order to acquire 2D serial, cross-sections of various paussines samples, with a resolution between 0.954 and 2.44 micrometers. The 2D images in high resolution are then processed using a high-performance computer system and Thermo Scientific™ Amira™ Software and Thermo Scientific™ Avizo™ Software for the reconstruction of 3D models. With these models, we will be able to conduct a morphological study of the most variable parts in the body of the genus Paussus using 3D geometric morphometrics (3D GM), as these integrative techniques allows to describe in a quantitative way even subtle differences between structures, so as to determine whether the striking diversity of phenotypes is caused by the host or by other factors, overlapping the results obtained with the molecular part of phylogeny. These innovative practices help to deepen the meaning of shape in insect biology, from both structural and evolutionary views. They will allow, in particular, to describe the relationship between phylogeny and functional morphology in the extremely variable species of the subfamily Paussinae

Primate penile bone symplesiomorphy disclosed: why a critical literature review is crucial?

PRIMATE PENILE BONE SYMPLESIOMORPHY DISCLOSED: WHY A CRITICAL LITERATURE REVIEW IS CRUCIAL? Federica Spani1, Gabriele Gentile2, Massimiliano Scalici1, Monica Carosi1 1 Department of Sciences, Roma Tre University, 2 Department of Biology, University of Rome Tor Vergata In order to reconstruct the evolutionary history of primate penile bone (baculum) we accomplished a thorough primary literature search and critical revision, collecting data about the occurrence of baculum in 306 primate species. Although our resulting presence/absence binary matrix was mapped onto the most complete primate phylogeny (N=367; Springer et al., 2012) the analysis was performed on 255 species since we had to exclude taxa either provided with occurrence data however missing in the phylogeny or viceversa. Based on data analysed it appears that the primate ancestor had a baculum which therefore is a symplesiomorphic trait for the entire order. Main results show 8 independent losses of baculum. Two cases in particular need to be deepened: the phylogenetic parallelism of loss in Lagothrix and Ateles and the exceptional presence of baculum in only one Tarsius species (T. syrichta) despite the absence in the whole genus. Our evolutionary scenario clarifies uncertainties recently reported by Schultz et al. (2016) who couldn’t set the ancestral state of baculum for the primate order. In that study, likely flaws were the literature source used (only reviews) which resulted in a low number of primate species included into the analysis (N=102), and the arbitrary choice of transferring occurrence data between congeneric species to maximize the covering of the phylogeny used. Our study confirms that a higher number of species can substantially modify results about the ancestral characterstate reconstruction of baculum. Future multidisciplinary investigations including potential correlates might contribute to disentangle both evolution and function of this neglected bone

Ancestral character-state reconstruction of baculum in Primates: why a critical literature review is crucial.

"ANCESTRAL CHARACTER-STATE RECONSTRUCTION OF BACULUM IN PRIMATES: WHY A CRITICAL LITERATURE REVIEW IS CRUCIAL" FEDERICA SPANI1 , GABRIELE GENTILE2 , MASSIMILIANO SCALICI1 , MONICA CAROSI1 1 Department of Sciences, Roma Tre University 2 Department of Biology, University of Rome Tor Vergata Selection pressures rapidly shape the anatomy of biological structures, usually affecting both their occurrence and form. This is the case of structures involved in copulatory system, as for example the penile bone (i.e. baculum), either detectable in the distal end of penis or covering its entire length. Recently, Schultz et al. (2016) reviewed this neglected topic attempting to map baculum evolution on mammalian phylogeny, using data from the literature. Among all species included in the analyses, there were also some primate species (N=102). However, they were not able to set the ancestral state of this character for the Primate order, probably due to both a low number of primate species included into the analysis, and several arbitrary choices in assessing some occurrence data. We accomplished a complete literature research and critical revision, collecting data about the occurrence of penile bone in 306 primate species. The resulting presence/absence binary matrix was mapped onto the most complete primate phylogeny by Springer et al. (2012) and counting 367 primate species. Starting from this species list, we matched our species list with tip labels of primate phylogeny by performing two analyses (1) including (N=367), and (2) excluding (N=255) taxa with missing data. By doing so we aimed at verifying whether a higher number of species could modify results about the ancestral state reconstruction of the character. No significative differences between analyses were found, rather a lower phylogenetic signal for the ancestral state of baculum. Main results show 8 independent losses of baculum, 2 of which need to be deepened: 1) in the Atelinae subfamily baculum losses observed in Lagothrix and Ateles genera might be interpreted as a phylogenetic parallelism (homoplasy); 2) in the genus Tarsius, only T. syrichta (Linnaeus, 1758) is reported to have a baculum, whereas remaining species apparently lost it, contrary to Schultz et al. (2016) who missed T. syrichta’s baculum presence, and therefore considered an absence of penile bone for the entire genus. Based on data analysed it appeared that the ancestor of primates had a baculum, which therefore is a symplesiomorphic trait for the entire order. Our study may finally clarify uncertainty reported by Schultz and colleagues, however further analyses including more primate species might help to disentangle both evolution and function of this neglected bone

Claw asymmetry in crabs: Approaching an old issue from a new point of view

Crabs are considered exceptional examples of antisymmetry resulting from the phenomenon of heterochely. Here we investigate morphometrically both the size and the shape of heterochely in 28 crab species, distributed unequally along a brachyuran phylogeny. We address the importance of investigating claw size and shape for interspecific comparisons by linking geometric morphometric outputs to phylogenetic data for 134 brachyuran species. New indices introduced as new sexual dimorphic characters of size and shape, namely heterometry (right chela size/left chela size) and heteromorphy (Procrustes distance between right and left chelae shape), revealed sexually dimorphic differences in diverse crab species. We demonstrate that both size and shape heterochely occur amongst the examined species, but there are no ecological correlations. Our study demonstrates that claw similarity between two or more species was due mainly to phylogenetic relatedness rather than ecological convergence, suggesting that claw morphological features could be useful morphological markers in phylogenetic studies. Although further investigation is needed, this study represents one of the first to thoroughly analyse the origin and evolution of heterochely within the Brachyura clade