Retention of ice-associated amphipods: possible consequences for an ice-free Arctic Ocean.

Recent studies predict that the Arctic Ocean will have ice-free summers within the next 30 years. This poses a significant challenge for the marine organisms associated with the Arctic sea ice, such as marine mammals and, not least, the ice-associated crustaceans generally considered to spend their entire life on the underside of the Arctic sea ice. Based upon unique samples collected within the Arctic Ocean during the polar night, we provide a new conceptual understanding of an intimate connection between these under-ice crustaceans and the deep Arctic Ocean currents. We suggest that downwards vertical migrations, followed by polewards transport in deep ocean currents, are an adaptive trait of ice fauna that both increases survival during ice-free periods of the year and enables re-colonization of sea ice when they ascend within the Arctic Ocean. From an evolutionary perspective, this may have been an adaptation allowing success in a seasonally ice-covered Arctic. Our findings may ultimately change the perception of ice fauna as a biota imminently threatened by the predicted disappearance of perennial sea ice.

[Diagnosis of ligament injuries of the ankle joint using exposures under pressure]. / Zur Diagnostik von Bandverletzungen des oberen Sprunggelenks mit gedrückten Aufnahmen.

Pressure exerted against the ankle joint during lateral exposures shows a typical form of subluxation of the talus in respect of the tibia if there has been rupture of the anterior fibulo-talar ligament. This displacement can be quantified by using the standard technique of Seiler and Holzrichter. Retrospective evaluation of exposures carried out with pressure in 206 patients with stretching or rupture of the ligaments of the ankle joint have shown that stretching can be diagnosed if the joint space reaches 7 mm, and a rupture can be diagnosed with a joint space of 11 mm. If there is a difference of more than 5 mm in the joint space of the two joints, a rupture is present. With these criteria, 85% of all ligament injuries can be correctly diagnosed. In the remaining 15%, early arthrography provides the necessary information.