Surface contrast enhancement of integumentary structures in X‐ray tomography

Micro-computed tomography (mu CT) has become standard in the biological sciences to reconstruct, display and analyse 3D models of all kinds of organisms. However, it is often impossible to capture fine details of the surface and the internal anatomy at the same time with sufficient contrast. Here we introduce a new approach for the selective contrast-enhancement of integumentary surface structures. The method relies on conventional and readily available sputter coaters to cover the entire sample with a thin layer of gold atoms. This approach proved successful on a diverse array of plants and animals. On average, we achieved a 14.48-fold gain of surface contrast (ranging from 2.42-fold to 86.93-fold) compared with untreated specimens. Even X-ray-transparent samples such as spider silk became accessible via mu CT. This selective contrast-enhancement, makes it possible to digitally reconstruct fine surface structures with low absorbance while the tissue-dependent grey value resolution of the inner anatomy is maintained and remains fully visualisable. The methodology is suited for a broad scientific application across biology and other sciences employing (mu)CT, as well as educative and public outreach purposes

First assessment of the endoparasitic nematode fauna of four psammophilous species of Tropiduridae (Squamata: Iguania) endemic to north-eastern Brazil

Tropiduridae (Squamata: Iguania) is a lizard taxon widely distributed in the neotropics. Among its representatives, some species are classified as generalists regarding habitat usage. Others exhibit a very restricted and probably relict distribution, and are strongly associated with predominantly sandy and dry habitats. Within this rather ecologically similar than phylogenetically closely related group we examined specimens of Eurolophosaurus amathites, E. divaricatus, Tropidurus hygomi, T. psammonastes for endoparasites. In all four species examined we recorded parasitic nematodes (Nemathelminthes: Nematoda). At least three nematode species were recovered: Parapharyngodon sp., Physaloptera lutzi and Strongyluris oscari, with Ph. lutzi being the most abundant parasite encountered in all lizard species examined. In spite of the hosts’ habitat specialization, these parasites are also found frequently in non-psammophilous tropidurid species as well as in other squamates. Individual species richness per lizard was low, with usually just one species parasitizing at a time. These are the first parasites registered for these tropidurids and constitute a total of six new host records

On the date and organ of publication for the endemic Gal\ue1pagos scorpion Centruroides exsul (Scorpiones: Buthidae) by Wilhelm Meise, with a revision of its distribution and type material

Volume: 41Start Page: 412End Page: 41

Remarks on the northeasternmost distribution of Elgaria coerulea principis Baird & Girard, 1852 (Squamata: Anguidae) in British Columbia

Volume: 60Start Page: 229End Page: 23

Variability in pulmonary reduction and asymmetry in a serpentiform lizard: The sheltopusik, Pseudopus apodus (Pallas, 1775)

Besides snakes, numerous lineages of squamates gave rise to limb-reduced and elongated (serpentiform) species, indicating the evolutionary success of this modification of the plesiomorphic lizard Bauplan. Concerted with a serpentiform habitus are several morphological adaptations, many of which also concern the structure and arrangement of the viscera, such as frequently a pronounced pulmonary asymmetry in which one lung is reduced or even absent. The European glass lizard or sheltopusik, Pseudopus apodus, is the largest species of the exclusively serpentiform Anguinae. Driven by pre-existing conflicting statements on pulmonary asymmetry, we examined the lungs of 14 sheltopusiks and compared the condition to 11 slow worms (Anguis fragilis). We consistently found the left lung pronouncedly shorter for the slow worm, but indeed a highly variable pulmonary asymmetry between left and right sides in the sheltopusik. This is the first verified case of such variability in pulmonary reduction for any serpentiform squamate and raises several questions about the underlying developmental program for this otherwise taxon-specifically conservative trait

Bone histological correlates for air sacs and their implications for understanding the origin of the dinosaurian respiratory system

Air sacs are an important component of the avian respiratory system, and corresponding structures also were crucial for the evolution of sauropod dinosaur gigantism. Inferring the presence of air sacs in fossils so far is restricted to bones preserving internal pneumatic cavities and foramina as osteological correlates. We here present bone histological correlates for air-sacs as a new potential identification tool for these elements of the respiratory system. The analysis of several avian and non-avian dinosaur samples revealed delicate fibers in secondary trabecular and secondary endosteal bone that in the former case (birds) is known or in the latter (non-avian dinosaurs) assumed to have been in contact with air sacs, respectively. The bone histology of this “pneumosteal tissue” is markedly different from those regions where muscles attached presenting classical Sharpey’s fibers. The pneumatized bones of several non-dinosaurian taxa do not exhibit the characteristics of this “pneumosteum”. Our new histology-based approach thus can be instrumental in reconstructing the origin of air sacs among dinosaurs and hence for our understanding of this remarkable evolutionary novelty of the respiratory system

Data from: Bone histological correlates for air sacs and their implications for understanding the origin of the dinosaurian respiratory system

Air sacs are an important component of the avian respiratory system, and corresponding structures also were crucial for the evolution of sauropod dinosaur gigantism. Inferring the presence of air sacs in fossils so far is restricted to bones preserving internal pneumatic cavities and foramina as osteological correlates. We here present bone histological correlates for air-sacs as a new potential identification tool for these elements of the respiratory system. The analysis of several avian and non-avian dinosaur samples revealed delicate fibers in secondary trabecular and secondary endosteal bone that in the former case (birds) is known or in the latter (non-avian dinosaurs) assumed to have been in contact with air sacs, respectively. The bone histology of this “pneumosteal tissue” is markedly different from those regions where muscles attached presenting classical Sharpey’s fibers. The pneumatized bones of several non-dinosaurian taxa do not exhibit the characteristics of this “pneumosteum”. Our new histology-based approach thus can be instrumental in reconstructing the origin of air sacs among dinosaurs and hence for our understanding of this remarkable evolutionary novelty of the respiratory system

LambertzEtAl_BiolLett_Bone-Histological-Correlates-AirSacs_ESM2

Interactive three-dimensional model of the Europasaurus holgeri vertebral neural arch