Studies of secondary osteons in ribs have provided a great deal of what is known about remodeling dynamics. Compared with limb bones, ribs are metabolically more active and sensitive to hormonal changes, and receive frequent low-strain loading. Optimization for calcium exchange in rib osteons might be achieved without incurring a significant reduction in safety factor by disproportionally increasing central canal size with increased osteon size (positive allometry). By contrast, greater mechanical loads on limb bones might favor reducing deleterious consequences of intracortical porosity by decreasing osteon canal size with increased osteon size (negative allometry). Evidence of this metabolic/mechanical dichotomy between ribs and limb bones was sought by examining relationships between Haversian canal surface area (BS, osteon Haversian canal perimeter, HC.Pm) and bone volume (BV, osteonal wall area, B.Ar) in a broad size range of mature (quiescent) osteons from adult human limb bones and ribs (modern and medieval) and various adult and subadult non-human limb bones and ribs. Reduced major axis (RMA) and least-squares (LS) regressions of HC.Pm/B.Ar data show that rib and limb osteons cannot be distinguished by dimensional allometry of these parameters. Although four of the five rib groups showed positive allometry in terms of the RMA slopes, nearly 50% of the adult limb bone groups also showed positive allometry when negative allometry was expected. Consequently, our results fail to provide clear evidence that BS/BV scaling reflects a rib versus limb bone dichotomy whereby calcium exchange might be preferentially enhanced in rib osteons.
Bone microstructure of domestic herbivores is still not completely understood. Indeed, works focused on the bone histology of numerous Mammalian species frequently led to misunderstandings because of the high number of variations such as the kind of bone, section orientation, species, breed and age. Moreover, attempts to identify the species in archaeozoological studies by a mere qualitative approach have not been encouraging and in recent years quantitative methods, based on image processing and statistical analysis, have appeared. The present study was undertaken to determine whether morphometrical and morphological differences exist in the compact bone structure of the femur and humerus between horses and cows. Measurements such as area, perimeter, minimum and maximum diameter of osteons and Haversian canals as well as the osteonal density were carried out on cross sections of eight humeri and eight femurs of the two herbivores investigated. In agreement with other authors, the qualitative investigation confirmed that the compact bone of horses and cows can be classified as dense Haversian tissue. Osteons of the horse were more numerous and composed of a higher number of well-defined lamellae when compared with the cow. Diameter, perimeter and area of osteons and Haversian canals were always higher in horses than in cows and this pattern could be related to the different locomotor behaviour of these animals.
A high number of differences exist in bone histological features depending on the species, breed, age and bone. Moreover, osteon distribution may vary in the different sides of a bone as a consequence of different biomechanical strains. The aim of this work was to study the distribution and morphology of osteons in different sides of the equine femoral diaphysis with the attempt to correlate them to the main strains operating on them. The following parameters of secondary osteons and Haversian canals were measured in the transverse sections of diaphyses: perimeter, area, minimum and maximum diameter, eccentricity and osteon population density. A typical Haversian tissue was observed with elliptic secondary osteons consisting in about 10 well-defined lamellae surrounding a circular Haversian canal. Quantitative analysis displays a different population density of secondary osteons depending on the side. The caudal and medial sides, where compression strains are higher, have more secondary osteons in comparison with the cranial and lateral sides, where tension strains are prevalent. These data suggest that secondary osteon population density may depend on the predominant strains. Even the elliptical shape of secondary osteons may be related to biomechanical strains, as their major axes are oriented cranio-caudally parallel to prevalent strains.
Biagi F., Piras F., Farina V., Zedda M., Mura E., Floris A., Franzoi P., Fausto A.M., Taddei A.R. and Carcupino M. 2016. Testis structure, spermatogenesis and sperm morphology in pipefishes of the genus Syngnathus. -Acta Zoologica (Stockholm) 97: 90-101.Testes, spermatogenesis and sperm morphology have been analysed in four species of the Syngnathus genus. All species show testes of unrestricted lobular type, characterized by a single germinal compartment, with central lumen, and an external tunica albuginea. The spermatogenesis occurs throughout a process of semicystic type, in which germinal spermatocysts open precociously, so germ cells complete maturation in the testis lumen. Amongst them, aflagellate and flagellate multinucleate cells are recognizable. This type of spermatogenesis may be therefore related to the reduced number of simultaneously mature sperm produced by syngnathids. Only one type of mature sperm has been identified in all examined species. It is always a monoflagellate cell, characterized by an elongated head. Elongated head has generally been correlated with the internal fertilization and/or to the production of spermatophore. As this is not the case of syngnathids, a possible function to explain the particularly elongated head of syngnathids is discussed.
Mouflon (Ovis aries musimon) and sheep (Ovis aries aries) are considered as the wild and domestic subspecies of the same species. A comparative study on the microstructure of mouflon and sheep femoral bone diaphysis is here reported. Bone microstructure is described for the first time in the mouflon. More than 200 secondary osteons from both subspecies were analyzed and qualitative evaluation was followed by quantitative determination of perimeter, area, minimum and maximum diameters of secondary osteons and Haversian canals. The basic structural patterns observed in both subspecies can be classified as plexiform and irregular Haversian tissue, in accordance with what reported in the literature for most ruminants. The presence of many secondary osteons in the mouflon means that the bone also consists of dense Haversian bone tissue. Statistical analysis demonstrated that mouflon secondary osteons are larger than in the sheep and made of a greater number of lamellae. Since mouflon and sheep are taxonomically closely related and their body size is very similar, the qualitative and quantitative differences here reported could be primarily explained on account of their different lifestyle. Indeed, the habits of wildlife typical of mouflons may lead to the presence of wide areas of dense Haversian tissue in that subspecies, as mechanical stresses are known to be related to number and size of secondary osteons. Finally, this analysis could provide a useful tool to recognize bones from different species, in forensic exam and archaeozoological studies as well.
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