Variability of dermal bones and other parameters in the skull of Amia calva

A sample of 84 dried skulls of Amia calva has been examined for variations in dermal bones and other parameters. One specimen was found with a single parietal and another with incomplete division of the parietals. Observations on parietal asymmetry, disposition of sutures, number and disposition of postorbitals, infraorbitals, number of dentary and premaxillary teeth, and tooth row/jaw length relations are quantified. Statistical analysis of five paired characters and dispersion analysis of 12 characters shows that the skull growth is isometric. Given a few measurements on a skull it is possible to predict several others.     

Sculpture and vascularization of dermal bones,and the implications for the physiology of basal tetrapods

Sculpture of dermal bones and their vascularization in basal tetrapods are closely connected. Ontogenetic data suggest that the large vessels that coursed to the superficial bone surface induced the formation of sculptural ridges and tubercles around their openings. Imprints show that the vessels continued on the bone surface and coursed within furrows or pits, where they were protected by the sculpture from mechanical damage. Dermal bone histology indicates a consolidation of the integument in basal tetrapods by strong, mineralized Sharpey's fibres in the sculptural ridges and tubercles, and by the presence of metaplastic tissue in several taxa. Because of the tight integration of bone and dermis, the large vessels were not able to spread over the sculptural elements, but instead had to pass interosseously. The diverse sculptural morphologies depend on the variation in height and width of the ‘nodal points’ and their connecting ridges, and in the size and shape of the enclosed cells and furrows. A principal component analysis (PCA) and discriminant function analysis (DFA) of 47 basal tetrapod taxa with 12 discrete characters shows that dermal sculpture is suited for distinguishing some main basal tetrapod lineages. Taxa that are interpreted as being largely aquatic have generally a more regular sculpture than presumably terrestrial ones. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 302–340.     

Inter‐ and intraspecific variation in the surface pattern of the dermal bones of two sturgeon species

Archaeological bone remains of sturgeon (Acipenser sturio/Acipenser oxyrinchus) from northwestern Europe are often identified to species on the basis of their surface morphology and then used to reconstruct the spatial distribution of the two species through time. The dermal bones of A. sturio are said to have an exterior surface pattern consisting of tubercles, while those of A. oxyrinchus are said to display alveoli. In the present paper, the validity of the surface pattern as a species‐specific characteristic is critically assessed. To this purpose, dermal plates from modern, genetically identified museum specimens were studied and the surface morphology observed in a series of archaeological remains was compared with the genetic identifications obtained on these same remains. The analyses show that the surface pattern of dermal bones is related to the size of the individual, with the pattern of small A. oxyrinchus being similar to that of A. sturio. In addition, variations in the surface pattern among the bones of a single individual and within the same bone have been observed. These findings explain previous conflicting results between morphological and genetic identifications and allow the formulation of some recommendations for more accurate morphological identification of isolated archaeological sturgeon dermal bones.     

Development of dermal bones related to sensory canals of the head in the fishes Ophicephalus punctatus Bloch (Ophicephalidae) and Wallago attu Bl. & Schn. (Siluridae)*

Studies based on about 18 larval stages of each of two fish (a snakehead and a catfish) supply data about the development of those dermal bones of the head which are associated with the latero-sensory canals. Comparisons are made with other fish, living and extinct.     

The sculpture and morphology of postcranial dermal armor plates and associated bones in gasterosteiforms and syngnathiforms inhabiting Estonian coastal waters

Lees, J., Märss, T., Wilson, M. V. H., Saat, T. and ?pilev, H. 2011. The sculpture and morphology of postcranial dermal armor plates and associated bones in gasterosteiforms and syngnathiforms inhabiting Estonian coastal waters. ―Acta Zoologica (Stockholm) 93 : 422–435. Five fish species inhabiting Estonian coastal waters (Gasterosteus aculeatus L., Pungitius pungitius (L.), and Spinachia spinachia (L.) of the order Gasterosteiformes and Syngnathus typhle L. and Nerophis ophidion (L.) of the order Syngnathiformes) are described on the basis of the sculpture and morphology of their postcranial dermal armor plates, as revealed and illustrated by SEM images. This study shows that the shapes of these superficial skeletal elements vary by species as well as by their position on the body, whereas the sculpture on the bones is taxon specific. The detailed features allow the identification of isolated fossil and subfossil remains and show promise for future systematics studies.     

The thickness of the walls of tubular bones

Some bones have slender marrow cavities and relatively thick walls. Others have wide cavities and thinner walls. Such differences are described by a quantity K , the ratio of the internal to the external diameter. A theoretical analysis shows that the optimum value of K , which allows the mass of a bone to be minimized, depends on whether the bone is selected principally for yield or fatigue strength, for ultimate strength, for impact strength or for stiffness. It also depends on whether the cavity is filled with marrow or with gas. The values of K found in the limb bones of mammals, birds and a few reptiles are surveyed, and compared to the theoretical optima.     

The dermal chromatophore unit

Rapid color changes of amphibians are mediated by three types of dermal chromatophores, xanthophores, iridophores, and melanophores, which comprise a morphologically and physiologically distinct structure, the dermal chromatophore unit. Xanthophores, the outermost element, are located immediately below the basal lamella. Iridophores, containing light-reflecting organelles, are found just beneath the xanthophores. Under each iridophore is found a melanophore from which processes extend upward around the iridophore. Finger-like structures project from these processes and occupy fixed spaces between the xanthophores and iridophores. When a frog darkens, melanosomes move upward from the body of the melanophore to fill the fingers which then obscure the overlying iridophore. Rapid blanching is accomplished by the evacuation of melanosomes from these fingers. Pale coloration ranging from tan to green is provided by the overlying xanthophores and iridophores. Details of chromatophore structure are presented, and the nature of the intimate contact between the chromatophore types is discussed.     

Recovery and identification of DNA sequences harboured in preserved ancient human bones.

A new method is presented to extract and identify specific DNA fragments from well preserved human bones, dating from three different time periods. Bone samples were thoroughly freed from surfacial contaminating DNA. Access to the inner bone spongiosum was achieved by removing the covering bone layers of the vertebra or sternum, whereas the patella, tibia and caput of the femur or humerus were cleaved with an iron saw. After the spongiosum was taken out, extraction of nucleic acids from this "sand" like material was performed by heating at 94 degrees C during 20 min in a buffer containing essentially minor concentrations of detergent, chelating and reducing agents. The extracts were used in various Polymerase Chain Reaction (PCR) protocols to amplify different human specific DNA fragments (originating from chromosomes X and 12). From 15 out of 20 bone samples human-specific gene fragments could thus be identified.     

Species identification and likely catch time period of whale bones from South Georgia

Skeletal remains of baleen whales killed during the onset of 20th century commercial whaling lie scattered across the shores and abandoned whaling stations of the subantarctic island of South Georgia. Here we report on genetic species identification of whale bones collected from South Georgia using standard historical DNA protocols. We amplified and sequenced short fragments of the mitochondrial DNA (mtDNA) control region from 281 available bone samples. Of these, 231 provided mtDNA sequences of sufficient quality and length (174–194 bp) for species identification: 158 bones were identified as humpback whale (Megaptera novaeangliae), 51 bones were identified as fin whale (Balaenoptera physalus), 18 bones were identified as blue whale (B. musculus), two bones were identified as sei whale (B. borealis), one bone was identified as a southern right whale (Eubalaena australis), and one bone was identified as a southern elephant seal (Mirounga leonina). The prominence of humpback, fin, and blue whale bones in the sample collection corresponds to the catch record of the early years of whaling on the island of South Georgia (pre‐1915), prior to the depletion of these populations.     

Histology of sculptured cranial dermal bones of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan

Kokartus honorarius from the Middle Jurassic (Bathonian) of Kyrgyzstan is one of the oldest and basalmost salamanders in the fossil record, and this taxon is useful for documenting a primitive caudate condition and patterns of character state transformations within Caudata. Here, we provide a histological analysis of its dermal bones based on two thin sections of a fragment of a sculptured dermal skull roof bone (squamosal?). The dermal bone histology of Kokartus is similar to that of basal crown-group tetrapods (e.g. temnospondyls, lepospondyls and seymouriamorphs) in the following features: the presence of basic pattern of organisation of dermal bones (diploë structure); the cancellous middle region occupies larger space than the compact cortices; active remodelling with the formation of numerous erosion bays and secondary osteons; high number of vascular canals with the formation a dense vascular network (= ‘rete vasculosum’); and parallel-fibred bone is a dominant type of primary bone matrix. Crown-group salamanders retained the diploë structure, but demonstrate features of simplification (in comparison with Kokartus): absence of pronounced sculpture, lower degree of vascularisation and lower degree of remodelling. The simplification of the histological structure is a derived feature for the Caudata which appeared during the transition from stem-group to crown-group salamanders.     

The photophysics of a Rhodamine head labeled phospholipid in the identification and characterization of membrane lipid phases

The organization of lipids and proteins into domains in cell membranes is currently an established subject within biomembrane research. Fluorescent probes have been used to detect and characterize these membrane lateral heterogeneities. However, a comprehensive understanding of the link between the probes' fluorescence features and membrane lateral organization can only be achieved if their photophysical properties are thoroughly defined. In this work, a systematic characterization of N-(lyssamine Rhodamine B sulfonyl)-1,2-dioleoyl-sn-3-phosphatidylehanolamine (Rhod-DOPE) absorption and fluorescence behavior in gel, liquid-ordered (l(o)) and liquid-disordered (l(d)) model membranes was performed. In agreement with a previous study, it was found that Rhod-DOPE fluorescence lifetimes present a strong sensitivity to lipid phases, becoming significantly shorter in l(o) membranes as the probe membrane concentration increases. The sensitivity of Rhod-DOPE absorption and fluorescence properties to the membrane phase was further explored. In particular, the fluorescence lifetime sensitivity was shown to be a consequence of the enhanced Rhod-DOPE fluorescence dynamic self-quenching, due to the formation of probe-rich membrane domains in these condensed phases that cannot be considered as typical probe aggregates, as excitonic interaction is not observed. The highly efficient dynamic self-quenching was shown to be specific to l(o) phases, pointing to an important effect of membrane dipole potential in this process. Altogether, this work establishes how to use Rhod-DOPE fluorescence properties in the study of membrane lipid lateral heterogeneities, in particular cholesterol-enriched lipid rafts.