Abstracts - Deutsche Zoologische Gesellschaft

Ecology Posters 141P EC.5 - ENFreeze tolerance in tardigrades – subzero temperature survival and supercoolingpointsSteffen Hengherr 1 , M. Roger Worland 2 , Franz Brümmer 1 , Ralph O. Schill 11Biological Institute, Zoology, Universität Stuttgart; 2 British Antarctic Survey, Natural EnvironmentResearch Council, Cambridge, UKMany limno-terrestrial tardigrades live in harsh and variable habitats where they experience extremeenvironmental conditions like draught, heat and subzero temperatures. By entering an extreme dehydratedstate known as anhydrobiosis tardigrades are able to survive heat stress and long draughtperiods. However, they also can be exposed to great daily temperature fluctuations in winter withoutdehydration. Survival of the resulting freeze/thaw cycles in an active state, requires either the abilityto tolerate freezing of the body water or mechanisms to decrease the freezing point (supercooling).Therefore we studied the survival rate of 9 tardigrade species by cooling them at five different ratesdown to –30°C and thawing up to room temperature at 10°C/h. The resulting moderate surival afterfast and slow cooling rates and a low survival after cooling at rates in between, may indicate theinfluence of a physical effect during fast cooling and the possibility to synthesize some cryoprotectantsduring slow cooling. The supercooling points (SCP) measured in individual specimens by usingDifferential Scanning Calorimetry (DSC) range in the different species between -11°C and -23°Cand showed no difference compared with SCPs of cold hardened specimens. These results indicatethat tardigrades are freeze tolerant and do not decrease their SCP with cryoprotectants synthesizeddue to cold hardening. This study is part of the project www.FUNCRYPTA.de, funded by the GermanFederal Ministry of Education and Research, BMBF (0313838)P EC.6 - ENDNA damage in storage cells of anhydrobiotic tardigradesSimon Neumann, Andy Reuner, Franz Brümmer, Ralph O. SchillAbteilung Zoologie, Universität StuttgartTardigrades are small metazoans, ranging in size from 0.2 mm to 1.5 mm. They live in micro-habitatswhich frequently undergo changes in the environmental conditions, e.g. periodic desiccation.In response to such unfavourable circumstances tardigrades can enter a state of latent life, knownas anhydrobiosis, which is characterized by a metabolic arrest and the transition of the animal intoa so-called tun state. In order to be able to recover without any apparent damage, tardigrades haveeffective adaptations to preserve the integrity of cells and tissues. Yet, animals can persist in thisanhydrobiotic state only for a limited period of time. With increasing duration of anhydrobiosis thesurvival rate decreases, although time spent in anhydrobiosis does not add to the usual life expectancyof tardigrades, and recovery is possible even after years in anhydrobiosis. Evidence suggests,that oxidative processes are the cause of damage during anhydrobiosis. These processes are mediatedby reactive oxygen species, whose primary target is the DNA. We adapted the Comet Assay forthe use with storage cells isolated from the tardigrade species Milnesium tardigradum and showedthat tardigrades sustain only minor DNA-damage during transition into the anhydrobiosis. However,the longer the specimens remained in anhydrobiosis, the more DNA lesions accumulated. This studyis part of the project www.FUNCRYPTA.de, funded by the German Federal Ministry of Educationand Research, BMBF (0313838).