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7
Content available Melanophores inside frogs
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EN
Melanocytes/melanophores were known for some decades as pigment cells in skin. The origin of these cells in embryogenesis from neural crest cells is actively investigated now. Some melanocytes/melanophores were described inside adult vertebrates. Historically, these internal melanocytes have been largely ignored, until recently. In frogs, the melanophores populate not only the skin, but all the inner connective tissues: epineurium, peritoneum, mesentery, outer vascular layer and skin underside. In adult avian, melanocytes were also found in visceral connective tissues, periostea, muscles, ovaries and the peritoneum. In mammals and humans, melanocytes are also revealed in eyes, ears, heart and brain. A black-brownish pigment, which can be found in brains of humans and some mammals, was called neuromelanin. Currently, attempts are being made to treat neurodegenerative diseases and various nerve injuries with medications containing melanin. In this micro-review, we wanted to remind again about the inner melanophores on visceral organs and lining blood vessels and nerves, their importance in organisms resistance to adverse environmental factors.
EN
This paper describes the vertebrate ichnofauna from the Tumlin Sandstone (Buntsandstein) of the Holy Cross Mountains in Poland. The footprint assemblage has previously been regarded as Early Triassic in age; however, ichnogenera characteristic of the Late Permian are now recognized. Lack of representatives of the ichnofamily Chirotheriidae, characteristic of continental Triassic sediments worldwide, also indicates a Permian rather than a Triassic age for the studied assemblage. Three ichnogenera (Batrachichnus, Limnopus, and Amphisauropus) produced by amphibians are recognized, the remainder (Varanopus, Chelichnus, Dimetropus, Rhynchosauroides, Palmichnus, Paradoxichnium, and Phalangichnus) being of reptilian origin. Batrachichnus cf. salamandroides (Geinitz, 1861), Limnopus cf. zeilleri (Delage, 1912), Amphisauropus cf. latus Haubold, 1970, Varanopus aff. microdactylus (Pabst, 1896), Chelichnus cf. duncani (Owen, 1842), and Dimetropussp. are recorded in the Lower Buntsandstein for the first time. The following new ichnospecies are erected: Rhynchosauroides kuletae ichnosp. nov., Palmichnus lacertoides ichnosp. nov., Paradoxichnium tumlinense ichnosp. nov., Phalangichnus gradzinskii ichnosp. nov., and Phalangichnus gagoli ichnosp. nov.
EN
Computer modelling related to the real dimensions of both the whole filament and the myosin molecule subfragments has revealed two alternative modes for myosin molecule packing which lead to the head disposition similar to that observed by EM on the surface of the cross-bridge zone of the relaxed vertebrate skeletal muscle thick fil­aments. One of the modes has been known for three decades and is usually incorpo­rated into the so-called three-stranded model. The new mode differs from the former one in two aspects: (1) myosin heads are grouped into asymmetrical cross-bridge crowns instead of symmetrical ones; (2) not the whole myosin tail, but only a 43-nm C-terminus of each of them is straightened and near-parallel to the filament axis, the rest of the tail is twisted. Concurrent exploration of these alternative modes has re­vealed their influence on the filament features. The parameter values for the filament models as well as for the building units depicting the myosin molecule subfragments are verified by experimental data found in the literature. On the basis of the new mode for myosin molecule packing a complete bipolar structure of the thick filament is cre­ated.
EN
We identified vertebrate scavengers of small mammal carcasses at the 780-km2 Savannah River Site during the winter of 2000-2001. Rodent carcasses, differing in size and visual conspicuousness, were placed in upland pine forests and bottomland hard­wood forests during six 2-week periods. Sixty-two of the 96 carcasses (65%) were removed by vertebrates. With the aid of remote photography, we identified 11 species of scavengers removing carcasses. Raccoons Procyon lotor, gray foxes Urocyon cine- reoargenteus, and feral pigs Sus scrofa scavenged most frequently. The mean elapsed time for carcass removal was 5.6 days. The number of carcasses removed by vertebrates did not differ significantly with respect to carcass size, visual conspicuousness, or habitat type; however, air temperature was strongly correlated (positively) with carcass removal. Our study demonstrates that many mammal species are capable of utilizing small carrion items as a food resource, and suggests that scavenging may account for a higher proportion of the diet of some facultative scavengers than is now widely assumed.
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EN
Conodonts, a large group of tiny extinct marine animals ranging in age from the Late Cambrian to Late Triassic (ca. 500 to 200 Mya), are usually considered as jawless vertebrates. Their only commonly occurring fossilized remains are minute, phosphatic, teeth−like elements of their feeding apparatuses. In most of the early conodonts the elements were conical and strongly elongated. Many of them are characterized by possession of a deep, longitudinal groove, usually associated with sharp edges or ridges. A comparative study of the grooved elements and venomous teeth and spines of living and extinct vertebrates strongly suggests that the groove in conodonts was also used for delivery of venom. Structural convergence of the conodont apparatus Panderodus with the grasping apparatus of chaetognaths, a group of extant, venomous invertebrate predators of similarly ancient origin, provides additional support for this conclusion.
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