Respiration of Cytherissa lacustris (Ostracoda) at different temperatures and its tolerance towards temperature and oxygen concentration.

The ostracod species Cytherissa lacustris was investigated with respect to its temperature and oxygen tolerance limits. In laboratory experiments the tolerance limits were found to be much wider than expected from field data. Hatching of first instars was observed in cultures up to 20° C. The tolerance limit for oxygen concentrations was less than 1 mg O2·l-1 at 10° C and 20 h exposure. The distribution pattern of C. lacustris along a depth profile in lake Attersee showed a maximum density between 10 and 20 m depth coinciding with temperatures between 4 and 15°C throughout the year. The size dependence of respiration rates of well adapted C. lacustris is within the normal range of small metazoans. Its weight specific rates of oxygen uptake indicate an adaptation plateau in the range between 10 and 15°C. Possible reasons and advantages of such an adaptation for C. lacustris are discussed.