Compensatory growth in tadpoles after transient salinity stress

Many freshwater habitats worldwide are being degraded by an anthropogenic increase in salinity. Although salt concentrations are known to fluctuate with variable freshwater inflows, we know little about what effects this may have on freshwater organisms. Using a species of frog, Litoria ewingii, we measured tadpole growth both during and after salt stress to determine their capacity to compensate or recover from this stress. During exposure to ecologically relevant concentrations of salt (5 , 10 and 15 seawater), tadpoles grew slower and were significantly smaller than those in our freshwater control (0.4 seawater). Upon return to fresh water, previously salt-exposed tadpoles grew faster than those in the control group, and by the eighth day of the recovery period, no longer differed significantly in size. The results of our study demonstrate a capacity for tadpoles to compensate for a period of environmental stress by temporarily increasing growth rate when the stress abates.