Biometric variation in three strains of Brachionus plicatilis as a direct response to abiotic variables

Morphometric variation in three clones of Brachionus plicatilis cultured at 20°C, 25°C and 30°C, and 9‰, 12‰ and 24‰ salinity was analysed. Size appeared to be largely under genetic control and this defined the narrow limits within which variation due to abiotic factors could occur. Temperature had a significant effect on size, but affected the three clones differently. The most general effect of temperature was a reduction in size which levelled off as the temperature rose. Of the measurements taken, only distance between the median spines was affected by salinity. An important inter-relationship between the effects of temperature and salinity was also detected.