The impact of the salinity of soil-water and food on the physiology, behaviour and ecology of salt-marsh Collembola

The impact of salt in soil-water and food was investigated on the osmotic and ionic regulation, behaviour, growth and reproduction of the salt-marsh dwelling Hypogastrura viatica (Tullberg). An experimental design was applied in which both factors were considered simultaneously. H. viatica regulated its osmotic concentration at soil-water salinities up to 50% S.W. At higher salinities it was an osmoconformer. Food salinity had no significant effect on the osmotic concentration of the collembolans. Both soil-water and food salinity had an effect on the ionic concentration of the haemolymph. A higher conductivity was measured at higher soilwater and food salinities. Both soil-water and food salinity also had a significant effect on growth and reproduction. At higher salinity the collembolans showed a lower feeding activity and consequently a lower growth and reproduction but the effect of the soil-water salinity was stronger than that of the food salinity. At an increasing salinity of the soil-water H. viatica showed a stronger avoidance of food of high salt concentration. Key-words: Collembola, salinity, salt marsh, marine littoral, osmoregulation, ionic regulation, growth, reproduction, mortality, behaviour