Morphological and histological characters of penile organization in eleven species of molossid bats

Microarchitecture of the penis bone (baculum) of a seal: A 3D morphometric examination using synchrotron and laboratory micro-computed tomography

We examined the ultrastructure of the mammalian os penis at the high-resolution synchrotron level. Previously, bacular microanatomy had only been investigated histologically. We studied the baculum of the harp seal (Pagophilus groenlandicus), in which the baculum varies more in size and shape than does a mechanically constrained bone (humerus). We (1) investigated the microarchitecture of bacula and humeri from the same seal specimens, and (2) described changes in bone micro- and macro-morphology associated with age (n = 15, age range = 1-35 years) and bone type. We analyzed cross-sectional geometry non-destructively through laboratory micro-computed tomography. We suggest that the midshaft may resist axial compression while the proximal region may resist torsion, based on measurements of cross-sectional and cortical areas, perimeter, ratio of maximum and minimum moments of inertia, and polar moment of inertia. In addition, midshaft bacula may be less mechanosensitive than humeri, based on microstructural variables (e.g., volume, surface area, diameter associated with lacunae and cortical porosity) analyzed across age groupings. Our findings related to the microarchitecture of the pinniped baculum provide a basis for further studies on development, mechanical properties, functions, and adaptations in this and other pinniped species. Our use of a multi-modal imaging approach was minimally destructive for reproducible and accurate comparison of three-dimensional bone ultrastructure. Such methods, coupled with multidisciplinary analyses, enable diverse studies of bone biology, life history, and evolution using museum collections.

HISTORY OF ORIGIN, ADVANTAGES AND DISADVANTAGES, VECTORS OF APPLICATION OF THE DIAPHONIZATION METHOD: CURRENT STATE OF THE PROBLEM

The article deals with the method of diaphonization, which consists in clarification and staining of tissues, organs and whole organisms for long-term storage in the form of preparations as one of the modern methods of morphological research and, in general, a powerful tool for studying the internal structure and topography of organisms. The authors have analyzed the history of the diaphonization method, its advantages and disadvantages. Its advantages include the ability to study the internal anatomy without destroying the object, detailing structures, preserving samples for further research, and the possibility of combining with other modern research methods. Despite its advantages, the diaphonization method also has certain limitations and disadvantages (possible deformation of structures, loss of color, time and space complexity, and limitations in application to certain types of organisms). With its three main application vectors (clinical, experimental, and botanical), the diaphonization method is an essential tool for researchers in many fields, which continues to evolve and find new applications, improving the overall scientific picture of understanding the structure of organisms and contributing to scientific progress. The article also highlights the importance and prospects of combining the diaphonization method with other techniques to determine a more accurate picture of the relative location and structural features of certain tissues, organs, and systems.

Penile shape discriminates two cryptic species of Akodon Meyen, 1833 (Mammalia, Rodentia, Cricetidae) from eastern Brazil

Glans penis morphology has been used as a powerful tool in mammal taxonomy to differentiate cryptic species. Neotropical rodent species Akodoncursor and A.montensis are cryptic, and interspecific hybrids are like their parental species. We investigated non-metric and metric phallic characters aiming to differentiate A.cursor from A.montensis. We also evaluated the parental species' influence of the phallic characters on hybrids. We analysed 96 male adults-56 A.cursor, 27 A.montensis, and 13 hybrids, subgrouping species by locality and hybrids by parental species (paternal vs maternal). We verified that A.cursor and A.montensis are distinguishable by penile-shape morphology: A.cursor has an elongated penile form with a flare in the distal portion and A.montensis has a barrel-shaped form. Also, dark spots in ventral view, if present in A.montensis, distinguish A.montensis from A.cursor. Although the non-metric characters differentiate the species, they do not distinguish the subgroups of A.cursor, A.montensis, and hybrids. The metric phallic characters indicated a significant difference between species and hybrids. These characters also differentiate the population groups of A.cursor. However, A.montensis subgroups and hybrids subgroups did not present a significant difference. This study shows the importance of penis morphology in the taxonomy of the cryptic rodent species A.cursor and A.montensis, representing a powerful tool to discriminate male specimens in mammal collections without karyotyping or sequencing, even though the specimens occurred in sympatric areas. Since most taxidermy protocols do not preserve the penis in mammal preparations, liquid preservation of some specimens or the removal of the penis before taxidermy for liquid preservation could be beneficial. We also recommend the organisation in museum collections of a penis bank for the A.cursor species group (or even all rodent species) to avoid losing this important information for species identification.

Range extension and species confirmation of Rhyneptesicus nasutus (Sind Serotine Bat) (Mammalia:Chiroptera) from Bajaur Agency, FATA, Pakistan

BACKGROUND

The lack of morphological differentiation among chiropteran species and cryptic speciation impedes species identification. DNA-based approaches help species identification and contribute to the discovery of additional species. Rhyneptesicus nasutus (Sind Serotine Bat) is a rare and poorly studied species in Pakistan.

METHODS

This study explores the range extension of Sind Bat within the territorial limits of Pakistan from Sind and Baluchistan to Federally Administered Areas of Pakistan. No molecular record exists for the species in Pakistan. In the present study, we for the first time confirm species identification of Rhyneptesicus nasutus from Pakistan using a genetic marker (cytochrome b) along with morphometric analysis. A neighbor-joining tree based on Kimura-2 parameters was created to infer phylogenetic relationships. We sequenced the cytochrome b gene segment and conducted a phylogenetic analysis with previously published data from other countries.

RESULTS

Sequences from Pakistan formed a clade with Iranian Rhyneptesicus nasutus specimens suggesting a common ancestry. Various morphometric parameters (mean values) were measured, including Head and Body length (44.3 mm), Tail length (43.4 mm), Hindfoot length (8.3 mm), Forearm length (35.7 mm), and Ear length 36 mm while 5th Metacarpal Length, 4th Metacarpal Length, and 3rd Metacarpal Lengths were 33.2 mm, 34.7 mm, and 35.3 mm. Approaches based on DNA barcoding reveal a high diversity of bat species in the study area.

CONCLUSION

The data will enable researchers to build an improved evolutionary framework of the Serotine Bats from this region and subsequently reconstruct a detailed evolutionary history of the genus. Further research is required to test other molecular markers to support the findings of the current study in Pakistan.

Formation, structure, and function of extra-skeletal bones in mammals

This review describes the formation, structure, and function of bony compartments in antlers, horns, ossicones, osteoderm and the os penis/os clitoris (collectively referred to herein as AHOOO structures) in extant mammals. AHOOOs are extra-skeletal bones that originate from subcutaneous (dermal) tissues in a wide variety of mammals, and this review elaborates on the co-development of the bone and skin in these structures. During foetal stages, primordial cells for the bony compartments arise in subcutaneous tissues. The epithelial-mesenchymal transition is assumed to play a key role in the differentiation of bone, cartilage, skin and other tissues in AHOOO structures. AHOOO ossification takes place after skeletal bone formation, and may depend on sexual maturity. Skin keratinization occurs in tandem with ossification and may be under the control of androgens. Both endochondral and intramembranous ossification participate in bony compartment formation. There is variation in gradients of density in different AHOOO structures. These gradients, which vary according to function and species, primarily reduce mechanical stress. Anchorage of AHOOOs to their surrounding tissues fortifies these structures and is accomplished by bone-bone fusion and Sharpey fibres. The presence of the integument is essential for the protection and function of the bony compartments. Three major functions can be attributed to AHOOOs: mechanical, visual, and thermoregulatory. This review provides the first extensive comparative description of the skeletal and integumentary systems of AHOOOs in a variety of mammals.

Morphological changes associated with Nile crocodile (Crocodylus niloticus) phallic glans inflation

The crocodylian phallic glans is the distal inflatable structure that makes the most direct contact with the female cloacal and associated reproductive tract openings during copulation. Therefore, its form and function directly impact female tissue sensory interactions and insemination mechanics. Compared to mammals, less is known about glans functional anatomy among other amniotes, including crocodylians. Therefore, we paired an ex vivo inflation technique with magnetic resonance imaging 3D-reconstructions and corresponding histological analyses to better characterize the morphological glans restructuring occurring in the Nile crocodile (Crocodylus niloticus) at copulation. The expansion of contiguous inflatable spongiform glans tissues is variably constrained by adjacent regions of dense irregular collagen-rich tissues. Therefore, expansion shows regional differences with greater lateral inflation than dorsal and ventral. Furthermore, this enlargement elaborates the cup-like glans lumen, dorsally reorients the glans ridge, stiffens the blunt and bifid glans tip, and putatively works to seal the ventral sulcus spermaticus semen conduit groove. We suggest how these dynamic male structures may interact with structures of the female cloacal urodeum and how these morphological changes, in concert with the varying material properties of the structural tissue compartments visualized in this study, aid copulatory gamete transfer and resulting fecundity. RESEARCH HIGHLIGHTS: Nile crocodile glans inflation produces a reproductively relevant copulatory structure directing insemination and female tissue interactions. Pairing magnetic resonance imaging 3D reconstruction with corresponding histology effectively studies functional anatomy.