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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1391

Yngvar Olsen, K.I. Reitan, and O. Vadstein; Dependance of temperature on loss rates of rotifers, lipids and w3 fatty acids in starved Brachionus plicatilis cultures. Hydrobiologia 255/256:13-20, 1993

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Rotifer cultures of Brachionus plicatilis (SINTEF-strain, length 250 um) rich in w3 fatty acids were starved for >5 days at variable temperature (0-18 degrees C). The net specific loss rate of rotifer numbers were 0.04 day-1 (range 0-0.08 day-1) at 5-18 degrees C, but reached values up to 0.25 day-1 at 0-3 degrees C. The loss rate was independent on culture density (range 40-1000 ind.ml-1), but was to some extent dependent on the initial physiological state of the rotifers (i.e., egg ratio). The loss rate of lipids was 0.02-0.05 day-1 below 10 degrees C, where the potential growth rate of the rotifer is low (0-0.09 day-1). The loss rate of lipids increased rapidly for higher temperatures where the rotifer can maintain positive growth, and reached 0.19 day-1 at 18 degrees C. The Q10 for the lipid loss rate versus temperature was higher than the Q10 for respiration found in other strains. This may suggest the other processes than respiration were involved in lipid catabolism. The content of w3 fatty acids became reduced somewhat faster than the lipids (i.e. in particular 22:6 w3), but the fatty acid per cent distribution remained remarkably unaffected by the temperature during starvation. The results showed that rotifer cultures could be starved for up to 4 days at 5-8 degrees C without essential quantitative losses of lipids, w3 fatty acids, and rotifers. The rotifers exhausted their endogenous lipids through reproduction (anabolism) and respiration (including enhanced locomotion) at higher temperatures. At lower temperatures, the mortality rate became very high.