INFLUENCE OF RAPID CHANGES IN SALINITY AND TEMPERATURE ON THE MOBILITY OF THE ROTIFER BRACHIONUS-PLICATILIS

The rotifer Brachionus plicatilis can grow in a wide range of saliniti es and temperatures, but rapid shifts in both salinity and temperature may result in immobilized, non-swimming rotifers. The goal of this st udy was to examine the effect of perturbations in temperature and sali nity on the swimming pattern of the rotifer. Only slight changes in mo bility were observed when rotifers were exposed to changes in temperat ure (from 20-degrees-C to 8-30-degrees-C) and to an increase in salini ty (from 20 parts per thousand to 30 parts per thousand). When the sal inity was reduced to 15 parts per thousand and 5 parts per thousand th e proportion of mobile rotifers was reduced to 50% and 5%, respectivel y. The rotifers were throughout more resistant to perturbations in tem perature than to those of salinity. Combined temperature and salinity perturbations compared to perturbations in each factor separately sugg ested a synergetic effect of temperature and salinity on the rotifers locomotion. Transfer from cultivation conditions to low salinity (5 pa rts per thousand) and high temperature (28-degrees-C) resulted in very low percent of mobile rotifers (0-10%). However, if the temperature w as reduced to 8-degrees-C concomitant with the changes in salinity, th e percent of mobile rotifers was 85%. Rotifers use a high share of the ir metabolic energy for locomotion, and it is therefore not surprising that perturbations in salinity and temperature may result in partial or complete immobilization.