Low Temperature and Polyploidy Result in Larger Cell and Body Size in an Ectothermic Vertebrate

Previous studies reported that low temperatures result in increases in both cell size and body size in ectotherms that may explain patterns of geographic variation of their body size across latitudinal ranges. Also, polyploidy showed the same effect on body size in invertebrates. In vertebrates, despite their having larger cells, no clear effect of polyploidy on body size has been found. This article presents the relationship between temperature, cell size, growth rate, and body size in diploid and polyploid hybridogenetic frog Pelophylax esculentus reared as tadpoles at 19° and 24°C. The size of cells was larger in both diploid and triploid tadpoles at 19°C, and triploids had larger cells at both temperatures. In diploid and triploid froglets, the temperature in which they developed as tadpoles did not affect the size of their cells, but triploids still had larger cells. Triploid tadpoles grew faster than diploids at 19°C and had larger body mass; there was no clear difference between ploidies in growth rate at 24°C. This indicates better adaptation of triploid tadpoles to cold environment. This is the first report on the increase of body mass of a polyploid vertebrate caused by low temperature, and we showed relationship between increase in cell size and increased body mass. The large body mass of triploids may provide a selective advantage, especially in colder environments, and this may explain the prevalence of triploids in the northern parts of the geographic range of P. esculentus.