Frequent Anomalies in Larvae of Common and Moor Frogs in Moscow area and in the Suburbs of Moscow, Russia

Abstract

We studied influence of anthropogenic pollution of spawning ponds on embryogenesis of the common and the moor frogs ( Rana temporaria Linnaeus 1758, and Rana arvalis Nilsson 1852) from the natural population of the urban and the suburban territories of Moscow. Counts of larvae with anomalies in samples, fixed at different stages, indicated that in Moscow city and in the suburban territory the anomalies occur with approximately equal frequency. Spinal curvature, bradygenesis and skin damage were the most common anomalies. Edema (hydropsy), anomalies in gills, pigmentation disorders and complete malformation were also observed. In both species at all sites, most of the larvae had only one kind of anomaly, but some of them had two or more. Morphometric analysis of the spinal curvature showed that in abnormal tadpoles the angle between the body planes and tail plates was significantly less than in normal tadpoles, and is observed the underdevelopment of the tail. This anomaly is lethal because such embryos are not able to swim normally at later stages of development. Histological studies showed that the causes of spinal curvature in dorso-ventral direction is usually caused by somitogenesis defects or incomplete rotation of somites. Differences between species were observed in frequency of the less common anomalies. For Rana temporaria , edema, as well as a combination of complete malformation and skin defects were typical, while for Rana arvalis — a combination of edema and slow time of development was most common. No significant differences in frequency and nature of the anomalies were found between these species. However, inter-annual variability was remarkable. This suggests that frequency of occurrence of anomalies depends on the annual environmental situation.