Intra-specific variation in Pelophylax ridibunda (Rana ridibunda) in Southern Iran: life history and developmental patterns

This study describes the influences of variations in life history traits and developmental patterns of Pelophylax ridibunda. The causes of this variation were investigated by comparing observed patterns of inter-populational differences from geographic variables. The aim of the study was to investigate whether embryos and larvae from different populations of P. ridibunda show the same pattern of development when they are reared in the same conditions in the laboratory and to find out further whether if any differences appearing in the pattern among populations is environmentally or genetically based. Egg masses of P. ridibunda were collected from four sites in Fars Province, Iran and reared in the same conditions. Samples from most of the developmental stages were fixed and clutch parameters were measured at early developmental stages. Morphological characters in embryos and larvae including egg diameter, growing size of embryos and larvae at different stages, external gill, cement gland and mouth parts structures were examined with light and scanning electron microscopy. Statistical analysis showed that the mean diameter of eggs and jelly coats were significantly different (p < 0.05) from each other in all four populations. In addition, variation among sites in developmental stage at time of embryos and larvae were found. The results also showed at least three different types of dental formula, two main branches of external gill on each side, and type A cement gland developmental pattern among the populations. Our data suggest that local adaptation may be responsible for life history, and morphometric and morphological variations among eggs, embryos and larvae of P. ridibunda. Further study is needed to quantify the relative contributions of the genotype and the environment to embryo and tadpole morphology and to assess the adaptive significance of morphological differences.