Ist eine intrazelluläre Eisbildung bei Tieren tödlich? Versuche mit Polypen der Gattung Laomedea

Many authors are of the opinion that intracellular freezing causes death of cells. Observations on organisms tolerating intracellular freezing have been regarded not convincing or exceptional. In this investigation, experiments dealing with polyps of the cnidarians Laomedea flexuosa and L. loveni are described. A special experimental procedure made it possible to induce, selectively, extra- and intracellular freezing or extra-cellular freezing alone. Ice crystals could not be observed directly, but darkening of the test individuals is indicative of ice formation in the cell; this darkening (flashing or black-out) always follows ice formation in the surroundings. Intracellular ice formation is endured for a short period of time (Fig. 1). Small differences in freezing temperature exert great influence on survival rates (Fig. 2). These depend also on the duration of exposure to freezing conditions. Freezing resistance is lower after intracellular ice formation; the difference, however, appears to involve quantitative rather than qualitative aspects, although intracellular ice formation could possible destroy protoplasmic structures.     

Grooves to tubes: evolution of the venom delivery system in a Late Triassic “reptile”

Venom delivery systems occur in a wide range of extant and fossil vertebrates and are primarily based on oral adaptations. Teeth range from unmodified (Komodo dragons) to highly specialized fangs similar to hypodermic needles (protero- and solenoglyphous snakes). Developmental biologists have documented evidence for an infolding pathway of fang evolution, where the groove folds over to create the more derived condition. However, the oldest known members of venomous clades retain the same condition as their extant relatives, resulting in no fossil evidence for the transition. Based on a comparison of previously known specimens with newly discovered teeth from North Carolina, we describe a new species of the Late Triassic archosauriform Uatchitodon and provide detailed analyses that provide evidence for both venom conduction and document a complete structural series from shallow grooves to fully enclosed tubular canals. While known only from teeth, Uatchitodon is highly diagnostic in possessing compound serrations and for having two venom canals on each tooth in the dentition. Further, although not a snake, Uatchitodon sheds light on the evolutionary trajectory of venom delivery systems in amniotes and provide solid evidence for venom conduction in archosaur-line diapsids.     

Critical loads and their exceedances at intensive forest monitoring sites in Europe

Intensive forest monitoring by means of harmonised methods has been conducted in Europe for more than a decade. Risks of atmospheric nitrogen and sulphur deposition are assessed by means of calculations of critical loads and their exceedances. In the present study throughfall and bulk deposition of nitrate (N-NO(3)), ammonium (N-NH(4)) and sulphate (S-SO(4)) show marked spatial patterns and temporal trends. In the period of observation (1999-2004), sulphate deposition on intensive monitoring plots decreased by about one quarter. This is in line with the reduction of S deposition by 70% since 1981 in Europe as a result of successful air pollution control politics under the Convention on Long-range Transboundary Air Pollution (CLRTAP). However, sulphate and especially nitrate and ammonium deposition were found to still exceed critical loads at many forest sites, indicating a continued need for further implementation of air pollution abatement strategies.