Effects of salinity on the survival, growth, development, and metamorphosis of Fejervarya limnocharis tadpoles living in brackish water.

We studied salinity tolerance and the effects of salinity on growth, development, and metamorphosis in Fejervarya limnocharis tadpoles living in brackish water. Specifically, we examined whether tadpoles exhibit adaptive plasticity in development when exposed to different salinities. Tadpoles collected on Green and Orchid Islands off Southeastern Taiwan were assigned to salinities of 0, 3, 5, 7, 9, 11, and 13 parts per thousand (ppt). The daily survival, weekly growth, and development of tadpoles were recorded until metamorphosis. More than 50% of tadpoles survived in 9 ppt for over a month, and a few individuals survived in 11 ppt for 20 days, suggesting that F. limnocharis tadpoles tolerate salinity better than the tadpoles of most species studied to date. Tadpoles at 9 ppt had lower survivorship, and retarded growth and development (from Gosner stage 26 to 35) compared to the other treatments. Tadpoles metamorphosed early at a smaller size as salinity increased, suggesting the existence of adaptive developmental plasticity in F. limnocharis in response to osmotic stress. Phenotypic plasticity in the age and size at metamorphosis in response to salinity may provide a means for tadpoles to adapt to the unpredictable salinity variation in coastal rock pools.