Acta Zoologica最新文献

In-ovo imaging using ostrich eggs has been described as a potential alternative to common animal testing. This approach is independent from small animal imaging devices as ostrich eggs provide good image quality on computed tomography (CT), MRI or PET scanners used in clinical routine examinations. However, questions regarding physiological development and systematic evaluation of image quality are open. This study aims at describing physiological development of ostrich embryos on serial CT scans. One hundred eggs (63 fertilized and 37 non-fertilized) were artificially incubated for 37 days. On developmental days (DD) 0, 10, 19, 22, 25, 28, 31, 34 and 37, CT scans were performed using a Siemens Biograph mCT40. Density of yolk, albumen and shell as well as volumes of air cell, egg content and egg shell were determined. In fertilized eggs, the size of different osseous structures was investigated. Detection of embryonal development was technically successful in 100%. Distinguishing of fertilized and non-fertilized eggs is achieved as early as DD 22. After that, continuous development is depicted and osseous structures become visible on DD 25. Ostrich eggs might open the door for preclinical imaging studies if small animal imaging devices are not available. This study contributes to the implementation of ostrich eggs as an alternative to common animal testing.

Brachycephalus is a small, endemic genus of anurans that occur throughout the Brazilian Atlantic Forest. Recent analyses corroborated the monophyly of two species groups within this genus (B. ephippium and B. pernix), whereas the B. didactylus group appears to be polyphyletic. Herein, we compare and describe the skeletal system of all species from the Brachycephalus ephippium species group. We investigated diagnostic characters that are potentially useful to delimit similar species, confirmed the previously proposed genus definition and added six extra characters. We propose an osteological diagnosis for each species of the B. ephippium group, evaluating and describing intraspecific variations. Our results suggest that adults of B. ephippium group have ornamented parotic plates, ornamented post-orbital crests, absence of quadratojugal and neopalatines, distal end of the otic ramus of squamosal expanded towards the parotic plate, reduced zygomatic ramus of the squamosals, posterolateral projection of the crista parotica, presence of ornamented spinal plates (except B. alipioi) and ornamented paravertebral plates. We highlighted the importance of including more than one specimen per species when dealing with miniaturized taxa. A comparison with other Brachycephalus species groups and with Ischnocnema was also provided. Lastly, we suggest some characters to be included in future phylogenetic analysis.

Late Pleistocene Ice Age spotted hyena remains are described from the “Unicorn holotype skeleton” gypsum karst site Quedlinburg-Sewecken-Berge, Germany (Central Europe). The hyena population consists of adolescent to late adult individuals (96% of hyena NISP; 15% of megafauna NISP) indicating a commuting den site type. The comparisons to other European bone assemblages support hunting specialization on woolly rhinoceros (19% of NISP) and horses (27% of NISP). Specialization on bovids (Bison/Bos) can be added for this site. The megafauna contain few Eemian warm period remains of a large horse Equus ferus fossilis. Most (95%) of the megafauna is attributed to the Late Pleistocene glacial (Weichselian/Wuermian). Horse bones are dominated by distal leg elements from the smaller Przewalski horses Equus ferus przewalskii (26% of NISP). The Unicorn “holotype” skeleton originates from a composed horse skull, vertebrae and front legs, whereas the elephant remains added to this biologically not valid species must have been a straight-tusked elephant tusk.

Neurodegenerative diseases afflict a significant percentage of the world's population. The human nervous system is unable to regenerate after an insult, or due to senility, while low vertebrates still exhibit this ability. Comparative neurobiology can increase knowledge about neuronal degeneration and regeneration. Anamni vertebrates retain the ability to regenerate up to large areas of the nervous system. The regenerative ability of central nervous system components depends on the phylogenetic distance between classes of vertebrates. It decreases during evolution. Teleosts can skilfully regenerate brain, spinal cord and retina. Amphibians and reptiles can only regenerate certain areas; spinal cord regeneration in reptiles is limited to axonal regrowth. Retina regeneration is possible in bird embryo but not in the adult. In this review, we analyse how the regeneration of neurons occurs in different classes of vertebrates, and how the study of these mechanisms could be applied to the search for new therapies for neurodegenerative disorders.

The objective of this study was to assess testicular morphology and spermatozoal structure spatially within the reproductive tract and temporally among seasons in the sauger (Sander canadensis). The testis exists as two separate lobes joined at the urogenital pore and were characterised as unrestricted lobular with seminiferous tubules terminating at the ventral periphery and coalescing dorsally on the main sperm duct. Differences were observed between the pre-breeding season (November) and breeding season (March), with every stage of spermatogenesis occurring in spermatocysts in pre-breeding season in contrast to only spermatozoa being present in the tubules and main duct during the breeding season. Longitudinal folds in the main duct epithelium increased in number with increasing proximity to the urogenital pore, greatly increasing epithelial height regardless of season. Sauger spermatozoa consisted of an ovoid head, a midpiece containing 2 – 4 mitochondria incorporated into the head and a single flagellum containing an asymmetrical lateral ribbon. Motile spermatozoa were found throughout the testis during the breeding season. A decrease in sperm concentration was quantified moving proximally, suggesting a hydration effect by the main duct epithelium during the breeding season. These observations fill an important knowledge gap regarding reproductive biology of this impactful recreational fish species.

Basal avialans have been the focus of numerous histological studies in the past decade, from which different osteohistological patterns have been described. In this review, we look at the osteohistology in selected specimens from the four major avian groups: the long-tailed Avialae (Archaeopteryx and Jeholornithiformes), basal Pygostylia, Enantiornithes and Euornithes. Developmental and evolutionary changes in the three major bone layers are observed throughout the bone cortex of the limbs, may it be interspecific or intraspecific. Most noteworthy is the adaptive change from the overall lamellar/parallel-fibered bone tissue to a fibrolamellar complex in the mid-cortex as of the basal Pygostylia, potentially even as of the Jeholornithiformes. This change is generally associated with an increase in the density and complexity of the neurovascular network. Another evolutionary-developmental feature is the progressive loss of post-natal growth marks as of the non-ornithurine Euornithes, indicative of uninterrupted bone growth as observed in extant Neornithes. Our comparisons of the osteohistological patterns allow us to better determine how and when specific features typical observed in the avian crown group developed, associated with external and internal factors, and how they lead to what is commonly observed in extant Neornithes.

The rostral epidural rete mirabile appears in many studies on cerebral vascularisation; however, its exact characteristics are poorly understood. Its structure and location have a mechanism of selective cooling of the brain, protecting the animal from hyperthermia and affecting the body water balance. The aim of this study was to analyse the structure of the rostral epidural rete mirabile along with its tributaries. The study material consisted of a total of 61 specimens from the deer family belonging to the European roe deer, red deer and fallow deer species and those belonging to the beef family: domestic cattle, European bison, domestic sheep and domestic goat. The rostral epidural rete mirabile in the families of this study is well developed. It is formed of many small arteries anastomosing with each other and its main tributary is the maxillary artery, which is an extension of the external carotid artery. Additionally, in cervids, blood is supplied by the condylar artery. Within the families analysed, there was considerable similarity in the plan of construction within the rostral epidural rete mirabile, with minor differences among individual taxa.

Toads are considered poisonous animals since they have a passive mode of defence relying on cutaneous poison glands, differently from venomous animals who can inject venom in predators/aggressors or prey. Toads of Rhinella marina group are generally large and have a broad distribution in South America, inhabiting a wide range of environments. In this paper, we studied the toads Rhinella icterica from the Atlantic rainforest, and Rhinella jimi from the Brazilian Semiarid Caatinga, analysing aspects of natural history and comparing their skin morphology, the presence of macroglands, their resistance to water loss and rates of water uptake. In periods of extreme drought, R. jimi uses rock cracks as refuges, exposing only the head and regions of accumulation of poison glands. The skin of R. jimi showed higher number of poison glands with hydrophilic content than R. icterica. R. jimi also had a thicker skin, which can be related to its superior resistance to water loss. It also showed high rates of rehydration in association with a peculiar behaviour using the limbs to spread water onto highly glandular skin areas, suggesting that poison glands may also act in water balance in addition to chemical defence.

The African pygmy hedgehog (Atelerix albiventris) is commonly considered as a pet animal, which makes it widely studied. This study focused on lingual morphology due to its relation to the type of food consumed. Light and scanning electron microscopy on the tongues of 3 adult male hedgehogs was performed. Five types of papillae were distinguished on the dorsal lingual surface: filiform (fork-like), conical, fungiform, vallate and foliate. Small conical papillae covered the dorsal surface of the apex, filiform (fork-like) papillae were found on the corpus, fungiform papillae were scattered among conical as well as fork-like papillae. Three vallate papillae localized on the lingual radix were arranged in an inverted V shape. Taste buds were opened to the circumpapillary sulcus. Histochemical analysis of seromucous salivary glands in the radix and purely serous glands in the vicinity of the vallate papillae showed the composition of their secretions in more detail. A comparison of the ultrastructure of the tongue within the family Erinaceidae was performed, as well as to species with similar feeding habits.

The anatomy of Squalus acanthias has been explored and investigated for the past 150 years. Despite being a relatively well-known species, some anatomical inaccuracies on the paired fins persist throughout the literature, such as the presence of suprascapular cartilages and the morphology of the articular region of the pectoral fin. This study reassesses and provides new descriptions of the paired fins of Squalus acanthias, including comparisons with other representatives of Squalidae, aimed to expand the anatomical information of these species. All examined species of Squalus have two sites in the scapulocoracoid for the articulation of the pectoral basals: one facet articulating with the propterygium and a condyle for the mesopterygium (or both meso- and metapterygium). Additionally, the scapulocoracoid does not have a scapular process. Squalus acanthias is unique for having a series of barrel-shaped elements in the anterior region of the scapula. These elements are lacking in all other examined species of Squalus and Cirrhigaleus (and sharks in general) and are likely an autapomorphy of S. acanthias.