The combined effect of temperature and salinity changes on osmoregulation and haemocyanin concentration in Saduria entomon (Linnaeus, 1758)

Global warming is having an impact on the temperature and salinity of Baltic Sea waters. Therefore, it is important to determine the conditions in which animals can exist and how these changes may influence their functioning. Hence, the purpose of this research was to determine the broad tolerance limits of temperature and salinity of the glacial relict Saduria entomon by studying its behaviour, osmoregulatory ability and haemocyanin concentration. This effect of temperature was confirmed in the laboratory for individuals acclimated to different salinity and temperature regimes. Changes in the physiological parameters of S. entomon at various temperatures (5.5-21.5 degrees C) and salinity levels (1-15 PSU) were recorded. There were statistically significant differences in haemolymph osmotic pressure under the influence of salinity and temperature. The mean haemolymph osmotic pressures were the lowest at 1 PSU at all the temperatures examined and the highest at 15 PSU and high temperatures 16.5 and 21.5 degrees C. The haemocyanin concentration decreased significantly with increasing temperature at 1 PSU. There was a significant difference in haemocyanin concentration due to salinity at temperatures of 5.5 and 10.0 degrees C (the haemocyanin concentration decreased with increasing salinity). The results showed that, although S. entomon is classified as a cold-water animal, it can survive at high temperatures above 16.5 degrees C at least for a short time, as it is capable of osmoregulation. The tolerance to temperature changes was better than expected.